Work piece surface treatment

[Detailed Description of the Invention]

The present invention relates to the disposal method of a surface of metal, and relates to a shot peening method which gives compression stress and a set organization especially to a surface of metal. Shot peening is particles, i.e., the processing method which consists of making a shot hit to the surface of the piece of processing. One of the important objects of peening forms remains compression stress in the surface of the piece of metal processing, and there is in improving the fatigue strength. Therefore, they can be effectively prevented from local tensile stress, a phase change, Deleting or a grinding scar, a small hole, and scratching, uniforming a crack etc. and functioning as a stress concentration point. In many cases, shot peening using the bead of glass which is not comparatively intense is used in the field of the gas turbine engine of an airplane, and it is used in order to raise the performance of the disk put to high fatigue stress, Behn, and a braid. A certain surface state by the in general spherical hollow where each shot particle usually left shot peening to the I got it surface is formed. It is solution intermediary Came that the efficiency of a gas turbine engine is improvable by smoothing highly the surface of the Aero foil of the compressor by which peening was carried out these days. In that case, 15AA (arithmetic average-2.54x10)^-5mm(10^-6It is preferred for it to be equal to an inch and Ra in ANSI B46-1-77, or to attain the degree of finish beyond it. however, Aero foil usual -- it is difficult to obtain the desired degree of smoothness, without changing the size more than tolerance level, since it is what has special outline shape. Therefore, it is preferred to use the grinding smoothing process using the mass medium which usually vibrates after a peening process. a deer -- this deletes the surface coat by which peening was already carried out as well as other surface treatment processes more than needed, and has last fear. Such a process tends to require great time. The improvement-ized methods simple at such a translation are necessity and intermediary To have. In peening, the size of a shot is selected according to the size of the piece of processing, and the desired degree of finish. Many bases of selection exist as shown by the specification of SAE(SOCIETY OF AUTOMOTIVE ENGINEERS) J444a. the size on the title of a shot is widely distributed from 4.75 mm to 0.075 mm -- usually -- cast iron or steel-casting material -- intermediary To have [ from ]. The bead of the glass which has a diameter on a title (1.4 mm thru/or 0.038 mm) is also used widely. As for the shot marketed, it is common to be on the title, namely, to have the diameter distributed in the range comparatively wide as a center in the average size. In addition, a shot tends to be crushed with use and the small fragment which has an acute projection comes to be contained. Even if shot peening finishes the surface coarsely and moreover uses the shot of fixed mass as a result, the result which becomes uneven [ the degree of finish ] is caused. Even if it acts as an intermediary also of the fixed peening strength, the shot of the diameter of a large has the tendency to attain the degree of surface finish smoother than the shot of a byway. However, since time great in order to complete peening is required and productivity is spoiled, the shot of the diameter of a large is not preferred. When the piece of processing has complicated shape and peening also of the surface inside a narrow gap must be carried out appropriately, the shot of the diameter of a large cannot be used. Therefore, it is supposed that it is preferred to perform shot peening using a small shot generally. In order to improve fatigue strength and except to obtain the various degrees of surface finish of the piece of processing, the shot-peening process of various forms has been used from the former. For example, the method for making the state where there is a spot to the surface smooth, from the first is indicated by the U.S. Pat. No. 937180 specification. In this method, the hard steel ball which passed a series of funnels falls to tabular processing Kataue placed on that lower part by inclining. In order to fabricate aluminum plate material, aluminum plate material is placed on a concave-like stand, and the method of making the ball which has low permeability in it hit is indicated by the U.S. Pat. No. 3705511 specification. A steel ball has a diameter of 3~6 mm, falls from the edge of a slope by the operation of gravity, and hits the surface of the board material made into the shape of intermediary concave also in the speed of 5 m/s of abbreviation. The piece of processing is moved, being put to the flow of the time shot which does not change more greatly [ in order to change eternally by remaining stress, it is enough, however ] than the curvature defined by the stand. Thus, in using the formed aluminum plate material as a panel of the wings of an airplane, the usual shot peening is performed after this molding process using S230 (~0.7mm) smaller shot, and it attains required homogeneous remaining stress so that the intensity to fatigue may be given. the main objects of the present invention have uniform remaining stress -- And -- it is in providing the method for manufacturing parts provided with the surface which has the smooth degree of finish. The method based on the present invention is based on research of the delicate correlation between the size of a shot, energy, peening strength, and the degree of surface finish. A spherical shot which has an in general uniform diameter of 1~2.5 mm, preferably 1.5~2 mm which exercises at an in general fixed speed to a piece of processing is made to hit in the present invention. Therefore, remaining stress and the degree of surface finish of 40 or more AA corresponding to peening strength of 0.1 or more mmN can be attained simultaneously. The degree of surface finish must also be 30 or more AA so that a shot may not be crushed and may always maintain the globular form. Having an in general uniform diameter means that most shots are what is distributed among less than about ±0.05 mm, i.e., ±5%. If this is said both in quality and in quantity, it means a uniform thing in about ±16% of range. In the present invention, the shot which should hit the piece of processing has speed of per second 2.5~7.8 m most preferably per second 1.4~12 m 15 m/s or less. Although this hit speed changes with desired peening strength and the diameters of the shot used, when a smaller shot tends to attain the general more strong peening effect, a high shot speed is used. In using gravity as a suitable accelerating method of a shot, hit speed will become uniform in about ±4% of range. The unit hit energy obtained as a result is 0.2x10.^-4~12x10^-4It becomes uniform in the range of Joule, i.e., ±25% of within the limits. The degree of surface finish finally obtained is dependent on the degree of surface finish before adding shot peening. In the case of the piece of titanium processing which has the degree of surface finish of about 40 or less AA from the first, the method based on the present invention can attain 15AA or the smoother degree of surface finish than it. When the piece of processing is what has the still better degree of smoothness from the first, finally the degree of surface finish which also reaches 6AA can be obtained. The degree of surface finish of the piece of processing is dependent also on the diameter of peening strength and a shot. When the higher peening strength about a fixed shot is generally used, the degree of surface finish which is not so smooth is obtained. However, when the bigger shot about fixed peening strength is used, the smoother degree of surface finish is obtained. For example, in order to obtain the degree of surface finish smoother than 15AA, peening strength must be about 0.30 mmN(s). When a 1.8-mm shot is used, peening strength can be carried out to to about 0.5 mmN(s). About the point that such a degree of finish smooth about fixed peening strength that the diameter of a shot is large is obtained, For example, about the peening strength of 0.20~0.30mmN used ordinarily, Although the degree of surface finish of 15AA needed if the shot quite smaller than 1 mm was used to the good degree of surface finish being obtained when a bigger shot than 2 mm was used cannot be obtained, Even if it uses the shot which has a diameter of 2 mm or more, a result with more than good it is not expectable. However, when big peening strength is generally needed, the shot which has a diameter up to 2.5 mm is useful. However, since peening (saturation) time becomes long and hit speed becomes small when the shot which has a diameter over a shot, especially 2.5 big mm is used, homogeneity is lost and good smoothing cannot be performed to the processing single surface which makes a concave. When a shot is accelerated with intermediary gravity also in the fall which is 0.1~6 m based on the device and method which are written in another patent application specification by the same applicant, a uniform speed needed in the present invention is obtained, and movement in which a shot is in general regular can be carried out. Therefore, according to the present invention, the former is impossible and it can obtain Oh shot-peening accuracy and the degree of surface finish at a low price. Also since the present invention improves the quality of the surface coat by physical vapor deposition (PVD) or plasma arc spray again, it can be used. For example, intermediary shot peening also of the 0.3~0.6-mm peening strength can be carried out for the field where MCrAlY PVD and plasma coating of a thickness of 0.13 m were carried out using a 1~2.5-mm shot, and it can be heat-treated. It can correct to the possible above with the peening method by the bead of the glass with which the projection in a surface coat and Depletion were accelerated by this by the air based on known art, and, moreover, can smooth a surface coat considerably. The PVD layer which has the degree of finish of 60AA is improved by the degree of finish of 25 thru/or 35AA, and the plasma coating layer which has the degree of finish of 300AA is improved by the degree of finish of 100 or less AA. When the method based on the present invention is applied to the piece of processing which has the edge of thin meat, such as Aero foil of a gas turbine engine, the piece of processing is operated so that the edge of the thin meat may not receive damage to the flow of the Collimation(ed) shot and desired remains compression stress may moreover be formed in the portion. This operation consists of making it put to the flow of the shot which is made to rotate the piece of processing carefully around an axis parallel to that edge and by which a part of edge was Collimation(ed), and it makes it a shot not directly hit to the center line of the edge. Therefore, one side of the Aero foil will be first put to the flow of a shot, the braid of a gas turbine engine will rank next, and the field of the another side will be put to the flow of a shot. When each field of Aero foil is put to the flow of a shot, Aero foil is rocked mainly in case of the axis, and each field of the edge is finished. The drawing of attachment of the suitable example of the present invention is explained below. The suitable example of the present invention explained below is related with surface finish processing of the braid which consists of a titanium alloy (what has Ti-6AL-4V weight ratio) designed in order to have been used in the compressor portion of a gas turbine engine. This suitable example aims at obtaining the degree of surface finish better than 15AA, and (let mm based on the Almen examining method be a unit) the remains compression stress of 0.25~0.30N. Both these parameters are explained in detail later. However, the method based on the present invention should understand that it is what can be used conveniently, in order to finish the piece of processing of other kinds and the metaled surface accompanied by the degree of surface finish to 40AA, and the peening strength of the range of 0.10~1.0N. The method based on the present invention uses the spherical shot which has a serious uniform size which is used for manufacture of a ball bearing to shot peening based on known art. The hardness of a shot needs to be higher than the hardness of the metal by which peening should be carried out so that it may not change while performing peening. There are carbon tool steels, such as AISI C1013 heat-treated by the hardness of Rc60 as a suitable material for carrying out peening of the Ti-6aluminum-4V which has hardness Rc40. As for a shot, it is preferred that it is the material which has comparatively big density like steel. Although the material of other kinds can also be used as a shot, there is a trade-off that the material into which the material which has big density and high hardness in many cases has small density with low cost [ like / it is high-cost and / ceramics ] it is has a small effect. While a shot performs peening, as shot material does not serve as small particles, it must not be crushed. The importance is explained below. Many of shots used in peening based on known art are based on standards, such as SAE-J827 about iron or a steel ball and SAE-J1173 about a glass bead, or MIL-SPEC-S-13165B, and they are Oh. The example of the size of a shot based on SAE and a MIL-SPEC standard is shown in the 1st table. The same data about three kinds of shots which consist of NL-10 which have 1.0 mm in diameter on the title used in the present invention, 1.8 mm, and 2.5 mm, respectively, and 18 Facial expression 25 is shown in this table. Now, according to this 1st table, it turns out that the diameter of the shot based on known art is carrying out Over distribution comparatively broadly. For example, it turns out that the thing of S550 grade has a diameter of the range of 1.18 mm ~ 2 mm, and when it is a glass bead of GB20 grade, it turns out that it is distributed over the range 0.125~0.300 mm in diameter. About the shot based on the present invention, it turns out to it that it is uniform by within the limits ±0.05 mm in diameter. About the shot based on SAE and a MIL-SPEC standard, since the diameter is distributed based on a normal distribution, a certain amount of detailed shot particles are contained. This is understood from there being no screen data corresponding to the column of 99 thru/or 100% of accumulation percentage. 100% of the diameters of Tottering of the grade of the shot used in the present invention to it are I'm stucks within limits with predetermined [ narrow ] based in general on NL grade. It is important that a shot is a globular form when carrying out the present invention. This means that the variation in the radius of the particles of a shot does not exceed about 2%. A required spherical degree should be grasped from a viewpoint of the homogeneous request of a size, and it is explained in detail below about Tottering. When the shot which has irregular shape is used, compared with a corresponding spherical shot, the smaller Some may be unable to attain a result with Then and the present invention preferred for giving a shock of bigger strength.

[Table]

[Table]

As described above, the present invention provides the method of carrying out intermediary shot peening also of the degree of smoothness which reaches 6AA smoother than 40AA in the surface of the piece of processing. In order to achieve this object, it is required to have the smoothness of the surface corresponding to the degree of surface finish which shot particles make profitably at least like. It is preferred that the surface of a shot has 6AA or the degree of finish beyond it preferably. However, when so high the degree of finish is not required, the shot which has about 30 AA and the low Comparison degree [ when ] of smoothness can also be used. A request which was described above about the degree of smoothness about the degree of surface finish of the shot especially in prior art is inside Ivy. The shot which has comparatively irregular shape peculiar to the microatomized metal particles has also been used. It is supposed that a shot which contains a fragment from the request about the degree of globular form and the degree of surface finish of a shot which were described above in the present invention will not be used. Shot particles must have in general fixed energy, when it collides with the surface of the piece of processing. The suitable method of attaining this is a method of dropping the shot which has a uniform size from the discharge gate which consists of a madreporic plate formed above the piece of processing at a very low uniform speed. By that cause, a shot will carry out free fall with gravity, and fixed acceleration power, i.e., collision speed, will be given irrespective of the size to a shot. The speed of the shot at the time of a collision is dependent on the height of the gate located above the piece of processing. Energy E per shot is E=0.5mv.²It is expressed with the formula to say. m is mass here and v is the speed of the shot at the time of a collision. Speed is v as known well.²It is expressed with a formula called 2gh. h is the distance between height, i.e., a discharge gate, and the piece of processing here, and g is acceleration due to gravity. Thus, the energy at the time of shot particles colliding with the piece of processing is proportional to h. If the shot particles which have sufficiently big mass also collide sufficient speed with the piece of intermediary processing, this plastic deformation by which plastic deformation happens and remains compression stress is formed in the surface of the piece of processing will change the outside of the surface of the piece of processing locally. As far as remains compression stress is concerned, the effect of shot peening can change in fixed quantity by strength I measured by the Almen specimen (SAE-J442 and AMS2430). According to this test method, the small piece of SAF1071 steel corresponding to reading of an Almen "N" range is clamped to a flat holding fixture, and shot peening is added to it. If a specimen is removed from a holding fixture, a specimen will curve by the remains compression stress applied to the surface by which shot peening was carried out. The Almen number is denoted by the number which shows the height obtained by the curve of this specimen considering mm as a unit in Then and this specification. In order to examine the limit of the present invention, it is I got it about many examinations to an Almen steel specimen, an AMS4928 titanium (Ti-6aluminum-4V) specimen, and the braid made from AMS4928 titanium alloy. Strength I of shot peening measured about the above-mentioned Almen steel specimen. The degree of surface finish of titanium is Ohio [ U.S. ] Bendix's Bendix Model QEH Digital Profilometer and. It measured using standard surface finish degree measuring devices, such as Amplimeter Peak Counter. Saturation time T is set using Then and an Almen specimen with the shot-peening parameter showing the time taken to complete surface peening. When the twice as many time as this is spent, it is defined as saturation time as time that increase of the strength of peening will be 10% or less. For an economical process of production, a thing with short saturation time is preferred. They are accelerated with gravity using the shot of various sizes, and I got it explains many experiments in detail about the result later. It is I solved it. that it may be better to use the case where it is better to use a small shot, and a big shot according to the data obtained from these experiments. However, it is I solved it. that the result of a request is obtained about the surface degree of finish and both of compression stress by using I will try it. and the parameter of the comparatively narrow range in an experimental result. Drawing 1 shows the saturation time in 0.025N about the shot of a homogeneous size which has various diameters which carry out intermediary movement also of the mass of a fixed rate per unit time. as the size of a shot becomes large -- intermediary To have in which saturation time is quite large -- things are understood. For example, if the diameter of a shot is increased 5 times from 0.5 mm to 2.5 mm, saturation time will increase by 18 times. Drawing 2 -- per unit time -- the mass of a fixed rate -- with, the change of saturation time to I about the flowing shot is shown. If I is large, saturation time will decrease quickly. This is based on the fact of being more effective, when the shot which has high energy, i.e., a high speed, transmits energy to the piece of processing. Drawing 3 shows the relation between fall h and peening strength I. It turns out that needed h increases quickly, so that required I is large therefore. In order to try to perform peening which has big strength, the shot of the diameter of a large which has big mass is chosen. as long as according to Drawing 3 it turns out [ in which I increases ] that it is alike, it takes and extremely big h is [ a thing ] needed and the remaining stress effect is made profitably like to a metal specimen -- in -- it turns out that there is a certain fixed limit. The slope of the straight line about the size of three kinds of shots is seen change irregularly in the graph shown in Drawings 2 and 3. Although there is few data about a shot 2.5 mm in diameter, it is thought that effective data is shown. It is thought that an irregular change of a linear inclination is based on the influence of the energy transfer phenomenon and rate effect which carry out I and change complicated as a function of the size of a shot, and it is thought that a peak is within the limits of 1~2.5 mm. It is I solved it. that the result which changes greatly with sizes of a shot is obtained when it investigates about an energy transfer phenomenon. The obtained result, ""single shot and a repetition surface-of-a-sphere shock Occurring remains plasticity distortion (Residual Plastic Strains Droduced by Single and Repeated Spherical Impact)"J.A.Pope and A.KMohamed, Journal of Iron Steel it is what is supported by Institute (1955) Vol.180, and the data shown in 285 - 297 pages", and moreover has fixed correlation -- I solved it.. The detailed explanation about the newly obtained data is omitted. The 2nd table shows the value of various parameters measured about the size of three sorts of shots. These parameters are peening strength. - I (N), fall - h, saturation time - T, The total degree of energy Et (it is product of the square of 1/2, lapsed time T, and shot collision speed to all the mass flows per unit area) efficiency-E finish (it is a Then shot at the ratio to the collision energy of the shot particles of what subtracted rebounding energy from collision energy) the energy transmitted to the piece of processing is shown -- transfer energy Etr (ratio of Et and Eff), and surface finish degree-SF -- intermediary To have [ from ].

[Table]

[Table]

Drawing 4 plots the data about the efficiency acquired from the 2nd table as a function of a fall about the size of a different shot. The 2nd table and Drawing 4 show the following. (A) In order to attain specific I, if the size of a shot is large, so high Et is required. (B) It is more efficient to use a bigger shot, in order to transmit kinetic energy to the piece of processing. (C) If a fall is set to about 0.8 m or less about a 1~1.8-mm shot, efficiency will fall rapidly. (D) When making a certain specific peening strength profitably like, and a bigger shot is used, it is necessary to transmit a lot of energy Etr. Suppose that it cannot touch any more in this specification about the hypothesis and the more detailed research based on the above-mentioned experiment. If a bigger shot than (A) is used in short, more energies will be consumed, and the conclusion that inconvenience which was described above when the (B) fall was small not only arises, but the transmission efficiency of energy falls can be obtained. These conclusions have suggested that it is preferred that all use a small shot. The relation between a fall in case Drawing 5 I is 0.25N, and the size of a shot is shown. The fall is decreasing geometric-progressive as the size of a shot increases. It turns out that h permissible if the size of a shot amounts to 2.5 mm ~ 3 mm from Drawing 5 becomes a small value which is 0.25~0.40 m. Thus, it must be avoided, in order that collision speed may serve as a small value of about 3 m/s or less and may enlarge influence of change of initial velocity, if a fall becomes small. As for the piece of processing rotated or tilted to the direction of the flow of the piece of processing which has the three-dimensional shape of Aero foil etc., especially a shot, height may change no less than 50 mm. In such a case, an effective fall may change, collision speed may be changed more than tolerance level, and the result I and the degree of finish may change with processing Kataue's points. When very small, an extremely big fall is needed and it becomes conversely, less practical like the case in shot peening of the kind of others [ size / of a shot ]. Thus, collision speed will be restricted by air resistance if a great fall is taken about a small shot. When a fall is generally not much great, it will be contrary to the request which the height of a device is so much needed and is going to enable it to deal with the shot of other types with one device. Generally, when a fall must be great, the cost of a device becomes high so much. Drawing 6 shows the degree of surface finish produced by processing the piece of processing which consists of titanium alloys during saturation time T by various peening strength by the shot of various sizes. About the specimen which has the degree of finish of 9AA from the first, the more the diameter of a shot is large, the more it turns out that the degree of surface finish becomes smooth. For example, as for a I got it case, the degree of surface finish of about 6 AA is obtained in shot peening by the strength of 0.25N using a 1.8-mm shot, and when the shot which has a diameter which is 1 mm is used, the degree of surface finish of 12AA is obtained. The more peening strength is large, the more Drawing 6 shows that the coarseness of the piece of processing obtained gets worse as for increase of surface finish, i.e., the degree. This understands that it sees the data about the shot which has a diameter of 1 mm and 1.8 mm. This is because the power of acting as the strength of peening increases becomes large and the degree of surface modification of the piece of processing becomes large. The degree of finish obtained with GB20 glass bead is also shown in Drawing 6. When making the degree of finish of about 40 AA profitably like, compared with what is obtained by the present invention, it turns out that the result obtained with this glass bead is quite bad. Drawing 6 shows the effective thing, when a shot (1 more mm and 1.8 mm) carries out shot-peening processing of the surface coarse from the first. For example, the panel to which the degree of finish of 42AA was made by GB20 comes to have the degree of finish of about 15 AA by carrying out shot peening for a 1.8-mm shot by the strength of 0.25N. Drawing 7 shows the smoothing effect. When a specimen smooth first from the first will become coarse, will rank next, and it will be smoothed in time T, if curves A and B are seen, and peening is continued further, it turns out that the degree of smoothing improves further. About a panel coarse from the first, as shown in curve C, the smoothing effect continues from the start to the end, and it turns out that the possible degree of finish is obtained to the utmost in time T. Curve D shows the action of the usual GB20 glass bead. Since the bead in which a certain grade was crushed is usually contained in GB20 glass bead, the degree of finish is not continuously improved so much for a line intermediary in peening. However, if peening is performed exceeding saturation time when the comparatively perfect, specially selected glass bead is used, it is possible to raise the degree of surface finish to 30AA. Although it is possible to improve the degree of surface finish of parts generally at any cases, the degree of finish finally obtained is dependent on the degree of finish of the piece of processing from the first. To make the good degree of finish profitably like rather than 15AA or it using a 1~2.5-mm shot, it is required for the degree of finish of the piece of processing to be better than about 40 AA from the first. Depending on the piece of processing, the scar of quite big machining and the surface coarseness in which others are [ being a surge and ] measurable exist. It is not for peening correcting such a remarkable surface defect. Therefore, please understand that the present invention is a thing comparatively about micro surface coarseness other than such a remarkable surface defect. As mentioned above, it is I solved it. that the smoothing effect of Desired is acquired [ peening ] at least in peening at the beginning of the line intermediary between saturation time T at a I got it case using a big shot. It is necessary to choose the shot which can obtain the desired degree of finish, and I from a viewpoint economical, of course in as short time as possible. The present invention relates to discovering an important parameter, when asking Future for such optimal parameter. Drawing 8 shows the important relation of the peening strength to the degree of finish based on the above-mentioned data. It turns out that the degree of surface finish is improved as I decreases. It turns out that S110 steel shot and GB20 glass bead do not bring about the result of a request. It turns out that only a big shot makes possible simultaneously the very smooth degree of finish, and sufficiently big I. The portion surrounded with the dashed line of the lower right corner of Drawing 8 shows the suitable degree of finish about the Aero foil made from a titanium alloy, and peening strength. The shot which has a diameter of 1~2.5 mm is usable. However, in making the degree of finish better than 15AA profitably like, it turns out that I can use a 1-mm shot only at The of the range up to about 0.30N. Although all data was not investigated, shot of at least 0.8 mm or less quite smaller than 1 mm seems not to be useful. Drawing 9 shows the relation with input energy E which is proportional to fall h as the data obtained above was described above. When making the degree of finish better than the peening strength of 0.30N and 15AA, or it profitably like, it asks for required energy from the curve of Drawing 9. Paying attention to desired strength 0.30N, it moves to the right as it is first, and asks for an intersection with the curve corresponding to a 1-mm shot. It moves downward from this intersection and is energy 10.^-4It can ask for Joule. It is easy to calculate fall h from the value of this energy. Next, it turns out that it moves upward and the degree of surface finish of about 15 AA is obtained from the value of these energies E, and the size of a shot in quest of an intersection with another curve corresponding to a 1-mm shot. Similarly bigger energy 1.8x10 about the peening strength of 0.30N, and a 1.8-mm shot from this graph than a previous example^-4Although it turns out that Joule is needed, it turns out that the degree of surface finish of smoother 8AA is obtained. Drawing 10 shows the relation between the size of a shot, and the degree of surface finish based on the same data as Drawings 8 and 9. When the size of a shot becomes larger than about 2 mm, it turns out that the degree of surface finish is not improved so much unexpectedly. Drawing 11 shows the comprehensive result of old data, and shows the shot size suitable in diagram. It turns out that the degree of surface finish is not improved so much to saturation time increasing quite quickly in the range whose shot size is 2~2.5 mm. If I becomes small, the loss of time will become much more remarkable and a fall will also become small. When smaller than 0.40N, the diameter of a shot needs to have I smaller than 2 mm, and I can use the shot which has a diameter up to 2.5 mm, when larger than 0.40N. When using a small shot of 1 mm or less, the degree of surface finish of the piece of processing worsens, and if I is large, a fall will become large too much. Therefore, it is desirable for the sizes of a shot to be 1 mm or more, preferably 1.5 mm or more. When the optimal result is obtained when an about 1.5~2-mm shot is used having put the above result together, and the shot which is 1~2.5 mm is used especially, it turns out that the result of having excelled more in respect of the degree of surface finish and compression stress compared with the thing of conventional technology in specific peening strength is obtained. It may be related when peening strength is more than 0.25N in old explanation, and depending on the case, the weak peening strength up to about 0.10N may also have useful Oh. extrapolating the straight line of the graph in a drawing or a drawing about this -- being certain -- grade grasp can be carried out. Since a required speed and fall become small too much if the shot which has a diameter of the biggest category of the ranges considered was used in order to realize weak peening strength, the shot which has a diameter of the smallest range of the ranges considered is used. The 1~2.5-mm shot particle made of steel used in our experiment has a ±0.05-mm diameter permissible error and about 7.8 specific gravity, and is Oh. Therefore, it is uniform within ±2.5%, and the diameter is Oh. The mass on the title of shot particles is 4~64x10.^-3The error of the mass between the shot particles which are g and have a diameter on the same title is ±6~15%, and is Oh. The minimum of these numbers corresponds to the shot particles which have a big diameter. The range of speed which can be used in the present invention is dependent on the restrictions about the method of accelerating the size of a shot required in order to obtain the energy for attaining desired peening strength, and a shot. In order to accelerate a shot, various methods can be considered, but a uniform speed is obtained and the method of moreover using gravity about the point of being easy is considered to be the most practical. Therefore, a practical use limit considered here has the range and relation of a possible fall. As for a fall, it is preferred that it should be 0.1 m or more and is 0.3 m or more, and it is most preferred that it is a range which is 0.6~3 m. It has influence important for the accuracy of peening required when too small, in order that a fall may have influence at collision speed with arrangement of Aero foil, or its controlled big change of movement and may achieve the object of the present invention by extension. Although the fall over 6 m is considered to be too large and not to be practical, it is not an impossible thing. If a fall is 0.1~6 m when the device written in the specification of the above-mentioned patent application is used, collision speed will be set to per second 1.4~12 m, and collision speed will be set to per second 2.5~7.8 m if a fall is 0.3~3 m. In this case, it is uniform at ±4% of within the limits, and collision speed is Oh. If it is going to attain the degree of finish of 30 or more AA by the shot-peening strength of 0.1~0.6N using a 1~2.5-mm shot according to Drawing 9, the energy per shot will be about 0.2x10.^-4From Joule to 12x10^-4It becomes Within the range of. When the method based on the present invention in the Aero foil consisting of titanium in order to attain the degree of finish better than 15AA or it by the peening strength of 0.25~0.30N is used, the energy per shot is 0.6x10.^-4From Joule to 3x10^-4It becomes Joule's within the limits. Although described above about having the serious influence for the result from which a peening parameter is obtained, please understand that that the mass and speed of a shot must be in general uniform is a meaning said in within the limits of the above-mentioned permissible error. The permissible error of mass and speed is cumulative in respect of influence on energy and peening strength. The permissible error range of the energy level in a shot flow is dependent on the relation between desired peening strength and the desired degree of finish, and the request in specific application. In order to secure the saturation time good generally which can be trusted in many cases, it is preferred to catch an energy level within about ±15%. In the error span of mass which was described above, the error span of Then speed is ±4% (namely, v) at ±6~15%.²When it is ±16% of But, the energy error acquired statistically is a number which can realize a result with Then and this good at about ±25%. The above-mentioned error should not be understood by the absolute meaning. It is because these experiments do not cover all cases although these errors are acquired based on much experiments. If the error about one certain parameter is small needless to say, the permissible error of another related parameter can be enlarged. When based on known art, an error of a peening parameter which was described above will be recognized to be an in general uniform thing. If the specification of the shot used in known art is referred to, the mass will vary 100% or more and a mechanical type or a fluid type acceleration means will be used, the big variation also about speed will arise. This means about energy that much more big variation arises. In order to carry out the present invention, it is necessary to attain an in general uniform shot speed. A uniform speed can be obtained if acceleration due to gravity is used. However, as long as the indispensable requirements for the present invention are satisfied, arbitrary shot acceleration means can be used. As for peening, it is most preferred to carry out within dry air. However, it is possible to carry out the present invention suitably under the environment of the others in a fluid or steam etc. depending on the case. Since the present invention is premised on using the shot of an in general uniform size, using the shot of the size of two or the kind beyond it is considered [ not being apparently contained in the concept of the present invention, either, or ]. In order to actually carry out the present invention effectively, most shots must have an in general uniform constant dimension. It is not in agreement with the concept of the present invention to use the quite bigger (a permissible error is exceeded) shot at a remarkable rate than a regular size. however -- even if the shot of a size with a small quantity of a certain grade is mixing -- a reason with secondary it sake -- good -- please understand that Then is also a thing which is better and by which it is contained in the concept of the present invention by the case where it is especially sufficient or is meaningless. The reason is explained below. Saturation time serves as a measure of the time required in order to form desired remaining stress. This is a function of the size of the energy which the surface of the piece of processing receives by the number of collisions, and each collision. Therefore, it has a relation to which saturation time is in inverse proportion to the flow of mass. If the shot accelerated with gravity from the data shown until now is used, it turns out that an intermediary with different mass of each shot also gets speed with all the same shots. And as the diameter of a shot is small, the peening strength becomes smaller small [ the energy ]. Therefore, when a 1.8 mm shot and a 1-mm shot are mixed, for example as the size of a shot is various, saturation time becomes long rather than the case where the shot of any one kind of size is used. It is because saturation time and peening strength are governed by only the shot of a large size and the flow of a mass flow is reduced considerably. It is only that that the shot of a small size is mixing by such a translation extends saturation time. When the shot of a small size collides with the piece of processing, the I becomes smaller than the strength of a request when the shot of a large size collides with the piece of processing. When the shot of a different size is mixing, it stops at the effect of the existence of the shot of a size small at most being minor, and ending. If the worst happens, the shot of a large size strikes the shot of a small size to the piece of processing, and applies it, and the shot of a small size is accelerated by excessive energy, and even when the degree of finish of the surface of the piece of processing gets worse locally, it is. Things other than the steel used in the above-mentioned suitable example as a material of a shot are also usable. The shot must show elastic character, when it moreover collides with the piece of processing, and a device more firmly than the piece of processing. Most things seem not to crush it in general, namely, not to have to crush, when it collides with some devices in processing Katamata. The good result is based on the relation between energy and a diameter. Therefore, the material of the low density on which it was projected, for example at a certain speed is although it is thought that the same effect as the material which is projected at a smaller speed, depends and has high density is demonstrated so that it may have the same energy, Since this cannot be said to not necessarily grasp an effect of the speed of a shot completely although it is qualitatively true, it cannot say that a result with the particles of small density which have the same energy, and not necessarily the same particles of big density is brought about. It cannot be denied that the level of absolute velocity is an important factor. This is being able to say also from the data of the 2nd table that is comparing a 1-mm shot with a 1.8-mm shot. If these two kinds of shots are dropped from a height of 1.22 m, they will attain the almost same degree of surface finish of abbreviation 11~12AA. This is understood if the data of a 1-mm shot in 0.24N of the 2nd table is compared with the data of the 1.8-mm shot in 6.38N. If a 1-mm shot is dropped from a height of 4.88 m, the same peening strength as having dropped a 1.8-mm shot from a height of 1.22 m will be obtained. This is understood from Drawing 3 and the 2nd table. However, the 1-mm shot which can be set in this case can attain the degree of surface finish of 21AA. According to these data, in order to have to use inevitably the material which has small density by a high speed, a limit is among the uses of the material which has small density, it is equal to steel or the material which has bigger density than it is considered to be desirable. As described above, these experiments were mainly conducted on the steel specimen, the piece of Ti-6aluminum-4V titanium alloy processing, and the specimen. Therefore, although it is thought that the obtained result is peculiar to such materials, it believes with that from which the result mostly approximated about other materials which have the same characteristic is obtained. That is, it is thought that a result with the same said of the general titanium alloy made into the object of peening based on known art, an iron alloy, and a nickel alloy is obtained. The present invention is useful also in various kinds of coats, and surface finish-machining, as described above about the MCrAlY layer with which the gas turbine engine braid made from a nickel super alloy was coated. It is preferred that such a coat etc. are preferably formed by physical vapor deposition (PVD) or plasma spray. Please refer to specifications, such as U.S. Pat. No. 3542530, said 3676085 No., 3918139, and 3928026, for a MCrAlY coat. The PVD coat may have a defect often called a leader. These are Depletion prolonged right-angled in a plurality of pillar-shaped organizations looked at by the coat in the field of a Along basis. Such [ usually ] a coat has the degree of surface finish whose thickness is the same in a Then basis and title top at about 0.13 mm. As for such a coat, according to the present invention, it is preferred to carry out peening, as the shot which consists of a hardened steel ball which has a diameter of 1.8 mm was described above. As for the collision speed of a shot, in the case of the coat of MCrAlY, Then shot-peening strength I will serve as the range of 0.47±0.5mmN at per second 4.7~6.3 m. A shot carries out plastic deformation of the coat, and closes the discontinuous leader portion which exists in a coat. In this way, a coat comes to have elastic remaining stress and a coat is smoothed. After shot peening is completed, a coat is heated by the temperature of 1040 ±14-degreeC under a vacuum or inactive gas. In this way, the density of the piece of processing becomes equal to the density of the solid metal which composes it about 100%, and before usually performing peening, what had the degree of surface finish of 50~60AA has the degree of surface finish of the order of 25~35AA. Next, the coat produced by doing in this way is compared with what was obtained based on known art. for example, the case where shot peening of the glass bead specified as GB20 (about 0.2~0.3 mm in diameter) in SAE J1173 is carried out by the conventional air promoting method -- peening strength -- about -- it is set to 0.47N. According to it, compared with the case of what depends the defect in a coat on the present invention, it turns out that the degree of surface finish of a Then coat is only improved at most by the shallower range only by Closed for a while even at 40~50AA, and that it is. This was in agreement also with the measurement result of the remains compression stress of the proof plate made from a titanium alloy obtained using X ray dispersion. The remaining stress state acquired using steel bigger shots based on the present invention will reach even the still deeper portion of a processing single surface. The present invention can be carried out also to a plasma spray coat. Such [ usually ] a coat has a smallness hole defect in which it was distributed over the whole in general uniformly. The MCrAlY coat has the density of about 6.77 g/c.c., and this is about 94% of the theoretical density of the solid. The degree of finish of this coat is usually an order of 250~370AA. As such a coat was described above, when peening is carried out, many of defects will be closed mechanically. And the surface of a coat will be smoothed by even the degree of finish of abbreviation 60~80AA. The density of a coat is [ this ] further further improvable under hydrogen or a vacuum atmosphere 4 hours and by heat-treating by the temperature of 1065~1093 degreeC. It is I solved it. for the density (i.e., 99% of the theoretical density) of about 7.14 g/c.c. to be attained according to the experiment. This experimental result is contrastive with the result of peening using the glass shot of above-mentioned GB20. That is, the degree of surface finish serves as abbreviation 100~150AA in that case, and, moreover, the density of a coat does not become so high. It is I solved it. that the exfoliation in the trailing edge of a braid does not compare with a case by glass bead peening based on known art, and does not become a problem suddenly by applying the present invention to the MCrAlY coat formed in the turbine blade of nickel alloy nature. In order that a shot may exercise regularly in line according to the present invention, arrangement of Aero foil is comparatively easy and it is avoided that a shot collides with the edge directly. When carrying out peening of the surface coat formed in metal bases, the diameter of a shot should be 1 mm or more, and Then, preferably the thing which Taxiest should also be 1.5~2 mm preferably in 1~2.5 mm are I solved it.s. About a coat with a thickness of 0.13 mm mostly used to the Aero foil of a gas turbine engine, shot-peening strength is good in it being more than 0.3N. This value can be enlarged to about 0.6N. When accelerating a shot with gravity, although the falls should just be 0.6 m or less of 0.3-m or more And, it is more preferred that it is 0.5~2 m. Cautions are required when it is going to carry out peening of the piece of processing which has the edge of thin meat like gas turbine engine Aero foil. Although it is preferred that a desired remains compression stress layer may be formed in an edge portion, the edge must not change greatly. Gas turbine engine braid 20 has an anti-Tsutomu Aero foil side in the junior and senior high schools which intersect perpendicularly with axis 30 and this as shown in Drawing 12. The braid has trailing edge 24 which is thin meat rather than front tip 22 and it. When it is going to carry out peening of such a piece of processing, it is first attached to holder 32. Along rotation is possible for this holder 32 on circular predetermined locus m, and it holds the surroundings of that direction of an axis in a field usually parallel to streamline 36 of the flow of shot 34. The piece of processing is tilted from the mean place in a certain maximum inclination position as each of the edge is shown in Drawing 13. Straight lines 41a and 40a are center lines of a front tip and a trailing edge, respectively. Now, if front tip 22 is observed, Aero foil will be tilted to the second reference position where intermediary center line 41a becomes right-angled from the reference position to the flow line of a shot about angle B. Subsequently, angle +C'' is also moved to intermediary position 73 from position 71, it returns to position 71 again, this is repeated, and peening of the upper half of the edge is carried out. Aero foil is turned by the shape of A holder, and it is made to exercise similarly for carrying out peening of the back of the edge. Similarly, first, trailing edge 24 also carries out intermediary rocking also of angle +C', ranks it next, makes Aero foil inside-out, and carries out intermediary rocking also of angle-C'. Under the present circumstances, it cannot be overemphasized that the piece of processing will be made to tilt to position 73, will rank next, will follow on tilting to position 72, each field of Aero foil will be put to a shot flow, and peening of a front tip and the trailing edge will be carried out simultaneously. The shot which carries out Along movement at arrows 52, 54, and 56 carries out the intermediary collision of the angle P which inclined on 26 d of surfaces of the piece of processing at tangent 53 to 41 d of center lines of 22 d of edges as shown in Drawing 14, but it does not collide right-angled to a tangent. The portion of the state of the compression stress shown as 50d of hatching portions in Drawing 14 arises as a synthetic result of stress pattern 152,154 formed by the collision of each shot which has reached the depth of portion 58 and is shown by arrows 52, 54, and 56. Angle C is chosen so that depth D of the portion which always meets a Then center line below by 90 * and by which peening was carried out may become a desired thing. Usually, depth D is chosen so that it may become 50 thru/or 100% of the depth (portion 58) of a stress state formed in opposite side portions 26d and 28d of Aero foil. Approximate rotation angle C for the edge of the specific piece of processing is curvature radius R of the edge, In depth [ of a compression stress state of the request in the center line of the edge ] D, and the reference position of the point 54 grade in Drawing 14, the angle of inclination of 45 * is also computable from depth [ of a stress state formed in the piece of processing ] q, when the intermediary shot collided. Namely, "C=45 *-cos^-1[R²+(R-2)²-q²/2R(R-D)] For example, about the parts whose curvature radii of the edge are 0.38 mm, the steel shots which have a diameter of 1.8 mm realize stress concentration coefficient 1.45. The depth in which a Then stress state is formed by 0.36N as for the peening strength on the field of the curved edge which makes 90 * to a tangent is 0.18 mm. When a shot also collides the angle of 45 * with the piece of intermediary processing, peening strength is set to about 0.25 N, and depth q of a stress state is set to 0.13 mm. If the above-mentioned formula is used, it turns out that tilting angle C will be 33.5 degrees. The suitable frequency of rocking movement of the piece of processing is per minute 20 cycles, and suitable peening time is 2~3 minutes. It is clear that it is possible to add various modification change and to carry out the present invention, without deviating from the concept of the present invention, if it is a person skilled in the art although the present invention was explained about the specific suitable example above.

[Brief Description of the Drawings]

Drawing 1 is a graph which shows the relation between saturation time and the diameter of a uniform shot. Drawing 2 is a graph which shows the relation of the different peening strength about the shot of a diameter and saturation time. Drawing 3 is a graph which shows the relation of the different fall about the shot of a diameter and peening strength. Drawing 4 is a graph which shows change by the fall of the energy transfer efficiency of shot peening, and the diameter of a shot. Drawing 5 is a graph which shows a fall required in order to obtain the peening strength of 0.25mmN about the shot of a different diameter. Drawing 6 is a graph which shows the degree of surface finish obtained by peening strength which begins and is different from a certain degree of surface finish about the shot of a different diameter. Drawing 7 is a graph which shows the change by the peening time of the degree of surface finish about the shot of a different diameter. Drawing 8 is a graph which shows the dependency between the degree of surface finish, and peening strength about the shot of a different diameter. Drawing 9 is a graph which shows the correlation between peening strength, the degree of surface finish, and the kinetic energy of a shot about the shot of a different diameter. Drawing 10 is a graph which shows change with the size of the shot of the degree of finish. Drawing 11 is a graph which shows the relation of the saturation time, the fall, and the degree of surface finish which change as a function of the diameter of a shot. It is a perspective view showing the gas turbine engine braid by which shot peening is carried out, rocking Drawing 12. Drawing 13 is a diagram end elevation of the Aero foil in which the rotation angle about each edge is shown. Drawing 14 is an enlarged vertical longitudinal sectional view showing the remains compression stress formed in the edge of the piece of processing shown in Drawings 12 and 13 of peening. 20 ... braid, 22 ... front tip, 22 d ... edge, 24 ... trailing edge, 26 d ... the surface and 28, 28 d ... surface, 30 ... axis, 32 ... holder, 34 ... shot, 36 ... a streamline and 40a, 41 a ... straight line, 41 d ... center, 44 ... line, 50 d ... a portion, and 52 and 54, 56 ... arrow, 53 ... tangent, 58 ... a portion, and 71, 72 and 73, 74 ... position, 152,154 ... stress pattern.