Production of roll plated with chromium

[Detailed Description of the Invention]

(Field of the Invention) The present invention relates to the manufacturing method of the chromium Float dull roll used mainly for rolling of the charge of a metallic material. (PRIOR ART) For example, there is a dull steel plate which carried out surface roughening to the bright steel plate with the smooth surface moderately according to dull finish in what is called a cold-rolled steel plate finished by cold-rolling. As a roll for rolling usually used by the final process of cold-rolling, a dull steel plate uses a dull finishing roll (dull roll), and is manufactured by transferring detailed unevenness of a roll surface on the steel plate surface. A dull beak part is worn out, the surface rough degree of rolled material falls, and a dull roll ceases to satisfy product specifications as it repeats use. In this case, it is although rolls are exchanged, and repair regeneration of the exchanged roll is carried out and it is re-used, The man day of discontinuation of the rolling work accompanying this roll exchange and roll repair, etc. cause the increase in the manufacturing cost of E board, A steel plate with the surface rough degree adjusted especially delicately recently comes to be called for, the roll used for the manufacture may also control surface dull processing highly using a laser beam, and, in such a case, the cost of roll repair becomes a remarkable high thing. therefore, the thing for which the abrasion resistance of a dull roll is raised -- a reduction of a roll cost, and by extension, reduction of a w4 temporary manufacturing cost sake -- for a person skilled in the art -- Awful -- it is an important issue. As an extended measure against a roll life, the most practical means is chromium plating of a roll surface. It is the art put in practical use by chromium plating art being various in itself, and it is also comparatively easy to attach the uniform coat excellent in abrasion resistance. However, in the dull roll which has unevenness in the surface, even if it carries out chromium plating, especially in a dull peak part, a crack arises in a plating layer in early stages of rolling for the high load of rolling, Since this serves as a reference point, and the unevenness of condensation and rarefaction and the pushing crack of a dull pattern will occur in the surface of a product steel plate and it will become faulty [ a product ] if rolling is continued with such a roll that causes exfoliation omission of a plating coat, the extended effect of I can not get it away and a roll life is deficient in exchange of a roll after all. Also out of the above-mentioned chromium plating, the method of using the roll itself as wear-resistant steel casting of a high alloy, raising hardness with surface hardening, or carrying out thermal-spraying Cladding of tungsten carbide or the ceramics of a certain kind as an extended plan of a roll life, is. However, the life of a roll extensible by these methods is only about at most 2 times, also has problems, such as a rise of material cost, a crack of a hardening layer and Padding layer, and exfoliation, and is hard to be called practical measure. (Object of the Invention) The present invention makes a subject most extension of the roll life according to ROM plating in a practical use target now. Chromium plating methods of the roll for rolling already include the proposal of JP,61-201800,A and a 61-202707 gazette. However, in these artificers' experiment, the extended effect of a large roll life is not acquired by the method proposed there, i.e., the method of reducing the rough degree (Rz) of the roll surface which serves as a ground before plating. In chromium plating of the dull roll used for rolling of the charge of a metallic material, an object of especially the present invention is to extend the use life of the plated roll sharply, and to rationalize the process of plating processing and to lower the cost of roll manufacture or repair. (Means for solving problem) When this artificer processed the surface of the roll by which dull processing was carried out on relevant conditions in advance of chromium plating and the rough degree was raised, his adhesion nature of the plating coat improved and he checked that the crack and exfoliation of the above plating coats by the high load at the time of rolling decreased. The present invention makes the roll of dull finish Crawling in "electrolysis solution, and it performs electrolytic treatment here, It is made to increase 1~50% from the threads per inch before electrolyzing the threads per inch of the roll surface shown by PPI, and let the manufacturing method of the chromium plating roll giving chromium plating to after an appropriate time by making the above-mentioned roll into the negative pole" be a gist. In the above-mentioned method, the roll surface before performing electrolytic treatment is considered as the dull finish with the rough degree according to the purpose of using a roll. the method of dull processing - any may be sufficient as the processing method etc. which use the electron beam which has been spreading outside the boat fishing shot blast method, an electrical discharge machining method, etc. recently, and a laser beam. the enlarged section of the roll surface which carried out dull processing by the shot blast method is shown in Drawing 1 -- in addition, on account of explanation, to a transverse direction, the figure expands a lengthwise direction about 50 times, and it comes out of it. Even if it gives chromium plating to a surface roll with such unevenness as it is, it is as above-mentioned that the adhesion nature of a plating coat is insufficient and the effect of roll life extension is small. In the present invention, electrolytic treatment of the roll is carried out in advance of plating, and the concavo-convex shape of the roll surface shown in Drawing 1 is converted, as shown in Drawing 2 (surface roughening). As 0 illustration which is the roll surface expanded sectional view as Drawing 1 with same Drawing 2, the early irregular pattern attached by dull processing is further corroded by electrolytic treatment, and the number of detailed unevenness increases. By the present invention, PPI (Peak Countp6r Inch) estimates increase of such unevenness. PPI is in a SAE standard as one of the notation of surface coarseness. In detail, although Naoji Kinoshita editorial-supervision "surface polish / finish technical collection" Nikkei technical books ■P and 233 have description, Drawing 3 explains the principle of measurement. For example, it asks for the section curve of a roll surface with the 90 degrees of sensing pin point angle, and the sensing pin type coarseness measuring instrument which uses the diamond of tip curvature-radius Xiang of 5micro. mean line of this section curve! It is alike, and it is parallel, and resembles the bottom and a top from mean line I, respectively, and sets peak count level ■ and ■ to 1micro Xiang distance. In for two points which peak count level ■ of a section curve and a lower part intersects (for example, between point A and points B, between point B and points C), When one or more points (X+ of a figure, Xz, and Xs ... point) that upper peak count level ■ and section curve cross exist, these threads per inch that are with a measurement length of 1 inch in between considering this as one mountain are set to PPI. In Drawing 3, if from A point to E point shall be 1 inch, PPI of this figure will be 3. Now, in the present invention, as the roll which dull processing is carried out and consists surface shape as shown in Drawing 1 is put into an electrolysis solution, a roll is made into the anode, electrolytic treatment (1 solution etching) is carried out and it is shown in Drawing 2, the number of the unevenness is increased. The threads per inch after the electrolytic treatment shown by this PPI are made to increase from the threads per inch before that by 3~50% preferably 1~50% in the 0 present invention which counts it as mentioned above as also shows PPI after this processing in Drawing 3. if the method of electrolytic treatment is that from which the increase in above PPI is acquired -- arbitrary 0 -- for example When using the liquid of the same composition as giving chromium plating (regardless of whether a cistern is made separate), it is usually temperature [ of 45~55 degrees ] C1 addition current (it becomes about [ 35^/dm"X8 minute ] conditions from 25^/d+m"X 3 minutes as it style pile density X time.). although, as for electrolysis etching by which it has been carried out in order to remove a surface inactive layer as activation processing of the ground of the usual chromium plating, the degree of moderateness has addition current for 30 A/dm"X 1~2 minutes, the increase in PPI is not seen and stopped in electrolytic treatment of this level. The increase in PPI is made into 1~50% in the present invention, It is because the effect on the adhesion disposition of a plating coat is not remarkable, and the adhesion nature of plating which the gloss of a roll surface is lost, and a tree-like crystal structure increases to the surface, and is given on it will fall on the contrary in the increase in less than 1% of threads per inch if it exceeds 50%. Although electrolytic treatment is preceded and alkaline fluid, such as caustic alkali of sodium, is used for degreasing which is not indispensable as for processing of this degreasing and washing desirably [ degreasing and washing the roll after dull processing ] on the occasion of degreasing of a base material, and the implementation of the dawn method from zero which performs washing, when carrying out usual and plating, Since much trouble by degradation of liquid will be caused if this liquid is carried into electrolysis or plating liquid of a next process, sufficient flush is required. That is, if a degreasing bath and a flush tub must be provided, therefore the process of this degreasing and washing can be skipped in order to degrease, equipment, saving of materials, and simplification of a process will be attained. When carrying out electrolytic treatment and making the threads per inch of surface unevenness increase after dull processing by the present invention, even if it omits degreasing and washing before this electrolytic treatment, chromium plating with sufficient adhesion nature can be given. The following experiments were conducted in order to check this. After giving dull processing of PPI 160 to the roll for an examination of 30 mmphi (quality of the material = 0.8chiC forged steel) by Si i'7 Tobrast, it divided into what performs a degreasing-flush, and the thing which is not performed, and performed electrolytic treatment and chromium plating. A treating solution and processing conditions are as in the 1st next table. 1st Table As shown in Drawing 5, partner material (JIS 545C) B of the same size as test roll A obtained by the above is combined, The transfer examination was done on condition of for pressure regulation oil amount-of-supply 80 cc/[ planar pressure 75 Kg/s+s" and number-of-rotations 5X10' ], the surface of test roll A was observed, and exfoliation of the plating layer was investigated. If that the existence of a degreasing-flush and the rate of increase of PPI by electrolysis arranged the result makes PPI of a roll surface increase from the result of the 2nd table by 3% or more by electrolytic treatment the 2nd table the 2nd table, Even if it skips degreasing before electrolytic treatment, and the process of a flush, it turns out that chromium plating with sufficient adhesion nature can be performed. Electrolytic treatment can be carried out using the liquid same as mentioned above as the liquid for chromium plating. Therefore, the surface rough degree is first raised by electrolytic treatment, polarity can be changed in the same cistern as the next, and chromium (making roll into the negative pole) plating can be performed. In this case, it is not necessary to provide an electrolytic treatment tub and a plating tub separately, and from on equipment, a part of roll surface is eluted in liquid, and trivalent ferric iron (Fe"°) increases as it is desirable, however electrolytic treatment progresses. Fe" increases -- saliva -- if chromium plating is performed in inside, electrical resistance increases, the high voltage is required, or the covering nature of plating will get worse (surroundings [ it attaches ]), and the problem of plating quality, such as roughness of a plating side and gloss loss, will crop up. the -- six -- a figure -- 30 -- m -- Peng -- phi -- x -- eight - a big building -- width -- e -- steel -- a ring -- the anode -- carrying out -- 142 -- chromium -- plating -- liquid (composition Nichrome acid 225g/1 and sulfuric acid 2.5g/ f) -- inside -- Te -- three -- OA/d+w -- " -- (-- seven --) -- current density -- having understood -- the time -- liquid -- inside -- Fe -- " -- quantity -- change -- being shown . In Fe''', the addition current (current density x energization time) of electrolytic treatment becomes 5 g/Il by 3000 OA/ds" and a part. Since it is satisfactory, however the above problems will arise so much if such liquid performs chromium plating even if Fe" will increase in this way, if it is only electrolytic treatment, it is obliged to exchange of liquid. Then, when [ this ] good [ to install an electrolytic treatment tub and a plating tub separately, and to plate by after electrolytic treatment changing a tub, especially when thinking the efficiency of chromium plating, and the stability of quality as important ], in the direction of the liquid for electrolytic treatment, Fe" is 50g / j! It can be used until it becomes a grade. The conditions of chromium plating, for example, the thickness of plating, are consideration about the operating condition of a roll, and the life demanded and others. It is decided by carrying out. In the dull roll used for refining rolling of a cold-rolled steel plate, it may be made into the plating thickness about an about 5~25micro big building. (OPERATION) The effect of making concavo-convex threads per inch increasing by the electrolytic treatment of the present invention is explained in more detail. - To In, the surface of the roll by which dull processing was carried out, for example in A shit Plast is irregular in three dimensions, as typically shown in Drawing 4, and to it, the peak is distributed in two dimensions. In such a rough side, if the threads per inch in one section increase by electrolysis, as compared with the rate of the increase, threads per inch will increase remarkably in two dimensions. - as an example, PPI 160 of the first stage is increased to 175 by electrolysis about the sample roll for an experiment -- having made (9.1% of rate of increase) -- time -- electrolytic treatment -- the number of peaks -- increasing -- not only -- the -- distribution -- uniform -- becoming -- things -- I understand . The surface area is increasing remarkably such the surface by which surface roughening was carried out. The adhesion nature of a plating coat is conjointly raised greatly with the anchor effect by increase in concavo-convex. In this way, even if it gives chromium plating to the surface which carried out surface roughening change [ PPI / hardly ], when rolling, the peak of these large number distributed uniformly pays the load of rolling equally, wear of a surface chromium plating layer, and a crack and exfoliation are reduced, and remarkable extension of a roll life is brought about. Generally, on the occasion of rolling using a dull roll, sideways load is also received to the tangential adjusting of a roll, i.e., a peak, and wear and destruction at the tip of a peak arise at the same time it receives strong perpendicular concentration load in the dull peak tip of a roll surface. However, with the roll it was manufactured by the present invention method and with which the number of peaks increased remarkably, the absolute value of the load to each peak is small, therefore exfoliation of a chromium plating layer and omission decrease. The 3rd table shows qualitative evaluation of the roll of an increase of PPI by electrolytic treatment which carried out chromium plating comparatively at this. It is clear also from this result that PPI's to which it is made to increase by electrolytic treatment 1~50% of range is suitable. 3rd Table In the electrolytic treatment conditions to which PPI is made to increase by 1~50% by the present invention method, ten-point average coarseness Rz does not change, or increases. 0 that whose this Rz is not decreased it is also one of the main points of the present invention -- for example After carrying out dull processing of the surface of the roll made from forged steel by a shot blast, when PP1160 was made to increase to 170 by the first stage by 30 A/dg+"X5 minute electrolytic treatment (6.25% of rate of increase), as for Rz, initial value 25 mu- only changed to 25.1 mu- (0.4% of rate of increase). A detailed description of the invention is carried out according to an example below. (Example 1) Dull processing was given to the surface of the forged steel roll for extra prize rolling between the colds of 600■phiX1700■l (Hv 850) by the shot blast. the nature of the acquired roll surface -- PPI =165, center line average coarseness Ra=2.5 am, and ten-point average coarseness Rz=27.0am -- (-- all were five average measured value). After degreasing and washing this roll with caustic-alkali-of-sodium liquid, electrolytic treatment was performed by making a roll into the anode on condition of the following. Bath composition ......... chromic acid: -- 225±25 gel sulfuric acid =2.5±Ig#! Bath temperature ......... 50 °C addition current ...... 30 A/deca"X -- the roll surface nature after this processing was Rz=27.0micrometer (it does not change) for 8 minutes PPI =180 (9 or 1% of increase), and Ra=2.5microsecond (it does not change). Subsequently, it was Hv 1050, when T11 private seal of washing and drying and there being no abnormalities in appearance was carried out and hardness was measured, after plating with 30 A/ds"x32 minute conditions by having made the roll into the negative pole in the same liquid and making the chromium plating layer of a 15micro view form. according to the above-mentioned procedure, PPI and PPI after electrolytic treatment prepare eight kinds of variously different rolls the first stage -- each -- it included in the nature rolling mill of a tone, rolling of the cold-rolled steel plate was presented, and the amount of rolling until a roll life is exhausted by wear of a plating layer, exfoliation, etc. (exchange and repair are needed) was investigated. Rolled plates and sheets of steel were made into the annealing material of JIS 5PCC, and, in the work roll of the upper and lower sides of the above-mentioned roll, and the bottom, rolling was nature rolling of a tone (1.0% of pressing-down rate). By the roll which carried out chromium plating by the present invention method to the amount of rolling of 180 tons of the naked (with no chromium plating) dull roll which shows a result in the 4th table, the amount average value of rolling is 2345. It is 1-A and the roll life is extended by about 13 times. In every roll to Neck 1-8 of the 4th table, exfoliation of plating did not arise but little extremely stable operation of variation was possible for it. Impossible width schedule rolling was also conventionally attained by dull wear of the steel plate passage part, and the quantity of production improved by leaps and bounds [ o'clock ] 300 tons /from 250 tons/o'clock. 4th Table (Example 2) Shot blast processing of the roll of the same size as Example 1 and the quality of the material was carried out, and it was considered as the dull roll of PPI =170, Ra=2.3 am, and a Rz= 25.0micro garden. It put into the electrolytic treatment tub (liquid composition is chromic acid 250g/1 and sulfuric acid 2.5g/ l) as it is, and was considered as the anode, without degreasing - washing this, and electrolytic treatment for 6 minutes was performed by 50 degrees of solution temperature C1 current-density 30 A/dm." The roll surfaces after this processing were PPI =183 (7 or 6% of increase), Ra=2.3 pm (with no change), and Rz= 25.2 (increase in 0 and 8chi). Next, the roll was moved to the chromium plating tub (i composition is chromic acid 230g/ l, and sulfuric acid 2.68/ffi') provided separately from an electrolytic treatment tub, plating for 25 minutes was performed by solution temperature 50degreeC and current density 3 OA/dm" by having made this into the negative pole, and chromium plating of 11-micrometer thickness was given. When this chromium plating roll was built into the refining rolling mill and having been examined for it to carry out said to Example 1, the amount of rolling was equivalent to the result of Example 1 which amounted to 2500 tons and performed degreasing-washing before electrolytic treatment. In this example, the electrolytic treatment tub and the plating tub were set aside as mentioned above. As a result, the concentration of Fe3+ in electrolytic treatment liquid increased in proportion [ almost ] to a roll processing number, as shown in Drawing 7. Thus, the liquid which Fe" increased is supposing it carries out electrolytic treatment and plating with one liquid since it cannot use for chromium plating, If liquid must be exchanged, however the Japanese oak is set aside like this example by about 1.000 roll processing numbers, electrolytic treatment can be carried out, without changing liquid to about 6000. on the other hand -- the direction of plating liquid -- almost -- Pe' -- " -- there was no increase, and since there was little degradation of liquid, the use life was prolonged by 3 times. (EFFECT OF THE INVENTION) In the above, the dull roll mainly used for rolling of a cold-rolled steel plate was made into the example, and was explained. However, of course, the manufacturing method of the chromium plating roll of the present invention is applicable to manufacture of the roll used for rolling of the board of not only steel materials but nonferrous metal, and other products also at manufacture of the pinch rolls and bridal rolls of those other than for rolling (for example, a pickling line), the rollers of a carrier line, etc. In short, the present invention is aimed at all in the cases of giving chromium plating on the roll (roll in a broad sense also including what is generally called a roller) of the dull finish which has minute unevenness in the surface in order to improve the abrasion resistance and other character. And according to the present invention as stated above, the roll excellent in exfoliation of a chromium plating layer and very little endurance of omission can be manufactured. - It is also still more possible to omit degreasing of a base material dull roll and a flush according to a situation, in that case, the effect of Step and equipment simplification is also large, and electrolytic treatment and plating may be carried out with the same liquid of one tub, and another advantage will also be born, if these are divided into a separate Japanese oak and performed. Thus, it is also one of the effects of the present invention that change of a process can be performed if needed.

[Brief Description of the Drawings]

Drawings 1 are an enlarged section mimetic diagram of the roll surface part by which dull processing was carried out, and Drawing 2, The enlarged section mimetic diagram of the surface part of the dull roll in which surface roughening was carried out by electrolytic treatment, and Drawing 3, It is a schematic illustration explaining the transfer test method in which the enlarged section mimetic diagram of the surface part of the roll for explaining the valuation method of the rough degree by PPI and Drawing 4 examine the eye squinting enlarged drawing of the surface of a dull roll, and Drawing 5 examines the endurance of a chromium plating layer, the figure showing concentration change of Fe" in liquid according [ Drawing 6 ] to the electrolytic treatment of a roll, Drawing 6 which measured Drawing 7 in the example, and the same figure -- it comes out.