Grinding method for cast cold-rolled sheet metal rolls

Abstract

To provide an evaluation method and a grinding method for a roll usable as a cast cold plate pressure roll.SOLUTION: An evaluation method for a cast cold plate pressure roll having an inner layer made of an iron-based alloy and welded to be unified with an outer layer made of an Fe-based alloy containing C:1.2-2.8%, Si:0.3-1.2%, Mn:0.3-1.5%, Ni:4.0% or lower, Cr:4.0-12.0%, Mo:0.5-9.0%, V:3.0-10.0%, W:0.01-10.0%, and N:0.01-0.1% by mass comprises evaluating a ratio Ra / Pa of an arithmetic average height Ra of a roughness curve to an arithmetic average height Pa of a profile curve by 0.65-1.0. A grinding method comprises grinding the roll with a feeding speed of a grindstone being 0.1-0.5 times of a grindstone width and a notching amount of 0.005-0.33 times of an average abrasive grain size by using a cBN grindstone having a grain size of an abrasive grain set at #60-#600 of JIS R6001 and a grindstone volume ratio of abrasive grains set at 10-30% during finish grinding.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for evaluating and a grinding method for a cast roll having a surface property usable for cold strip rolling.

Background Art

[0002] As cold strip rolling rolls used in tandem rolling mills, single stand reversing rolling mills, etc., generally forged rolls containing about 5% Cr are used. In recent years, due to the hardening of the rolled material such as ultra-high strength steel and electrical steel sheets, the difficulty of rolling has been increasing, and accordingly, the demand for rolls having wear resistance and roughness retention has been increasing. Currently, forged rolls used for cold strip rolling are materials containing Cr as a main alloy element such as 5% Cr material, materials added with elements such as V and Mo, or materials called semi-high speed steel and high speed steel. In order to further improve the performance, it is effective to increase the amount of hard carbide forming elements such as Cr, Mo, V, W, etc., and add corresponding carbon to crystallize as coarse carbides at the austenite grain boundaries to increase the hard carbide content. However, materials with such increased carbides are likely to cause forging cracks starting from the coarse carbides when forged. Therefore, there is a limit to the high alloying for improving the wear resistance and roughness retention of forged rolls.

[0003] The surface texture of the roll is transferred to the surface of the rolled material by rolling. In cold strip rolling, since the transfer rate is high, the surface property of the roll surface in the grinding performed for each rolling needs to keep the surface roughness within a certain range and also requires that feed marks, chatter patterns, grinding burns, etc. do not occur. In addition, since the rolls incorporated in the rolling mill are replaced every few hours, the efficiency of the grinding operation performed each time is also an important factor in selecting the roll material.

[0004] In cold sheet rolling, including tandem rolling mills, it was known that cast rolls had superior wear resistance and resistance to surface roughness degradation compared to forged rolls because the carbide content could be increased beyond the limits of forged steel. However, increasing the amount of hard carbides such as Cr, Mo, V, and W, which contribute to improved wear resistance and surface roughness degradation, made grinding difficult. Achieving the required surface roughness for cold sheet rolling rolls, as well as a uniform grinding surface free from feed marks, chatter patterns, and grinding burns, was extremely difficult. Due to these grinding problems, cast cold sheet rolling rolls containing a large amount of hard carbides had not been put into practical use.

[0005] As a cast work roll for cold rolling, Japanese Patent Publication No. 11-302777 (Patent Document 1) discloses a cold rolling work roll in which the outer layer is formed by a continuous casting build-up method, with the components being C: 0.8~2.0%, Si: 0.3~2.0%, Mn: 0.3~2.0%, Cr: 4.0~10.0%, Mo: 1.0~6.0%, V: 0.5~3.0%, W: 3.0% or less, with the remainder being Fe and unavoidable impurities.

[0006] However, the composite roll described in Patent Document 1 limits the V content to 3.0% or less on the grounds that it would hinder grinding performance. V is an element that forms extremely hard granular carbides, and restricting its content presents a problem in terms of insufficient wear resistance and resistance to roughness degradation.

[0007] Furthermore, Japanese Patent Publication No. 2004-114048 (Patent Document 2) discloses a wear-resistant cold rolling roll characterized in that the outer layer contains, by weight %, C: 1.5-3.5%, Si: 0.3-2.0%, Mn: 0.3-2.0%, Ni: 3.0% or less, Cr: 4.0-10.0%, Mo: 1.0-15.0%, V: 3.0-9.0%, W: 10.0% or less, with the remainder being Fe and unavoidable impurities.

[0008] However, because it contains a large amount of V, which forms hard carbides, there was a problem with feed marks and chatter occurring during finishing processes.

[0009] Japanese Patent Publication No. 5-57583 (Patent Document 3) describes a method for grinding rolling rolls, characterized by adjusting the feed rate for finishing during grinding within the range of 80 to 500 mm / min and controlling the surface roughness of the ground roll within the range of Ra: 0.05 to 1.2 μm.

[0010] The rolling mill roll grinding method described in Patent Document 3 did not take into account the size of the grinding wheel during finishing, which sometimes resulted in feed marks. In particular, when grinding rolls containing a large amount of hard carbides such as V, which are difficult to grind, there was a problem in that a uniform ground surface could not be obtained by controlling the feed rate during finish grinding alone. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 11-302777 [Patent Document 2] Japanese Patent Publication No. 2004-114048 [Patent Document 3] Japanese Patent Application Publication No. 5-57583 [Overview of the project] [Problems that the invention aims to solve]

[0012] Therefore, the object of the present invention is to provide a method for evaluating the grinding surface of cast rolls that contain large amounts of hard carbides such as Cr, Mo, V, and W, which are highly wear-resistant and difficult to grind, and which can be used for cold plate rolling, as well as to provide a grinding method that can be used for cold plate rolling. [Means for solving the problem]

[0013] In view of the above objectives, the inventors have conducted diligent research and have discovered that a good ground surface for cold rolling can be obtained by grinding a cast roll with a composition excellent in wear resistance and resistance to roughness degradation using a grinding wheel with cubic boron nitride abrasive grains (hereinafter referred to as a cBN grinding wheel), and by evaluating the roughness after grinding not only by Ra but also by the Ra / Pa value, which is the ratio to Pa. This led to the present invention.

[0014] In other words, the present invention provides an evaluation method for cast cold-rolling rolls, wherein an inner layer made of an iron-based alloy is welded and integrated with an outer layer made of an Fe-based alloy having a chemical composition on a mass basis containing C: 1.2-2.8%, Si: 0.3-1.2%, Mn: 0.3-1.5%, Ni: 4.0% or less, Cr: 4.0-12.0%, Mo: 0.5-9.0%, V: 3.0-10.0%, W: 0.01-10.0%, and N: 0.01-0.1%, with the remainder being Fe and impurities, and the cold-rolling roll is characterized in that the cold-rolling roll is used for cold-rolling when the arithmetic mean height Ra of the roughness curve of the outer layer surface and the arithmetic mean height Pa of the cross-sectional curve satisfy equations (1) and (2). 0.20 μm ≤ Ra ≤ 1.0 μm (1) 0.65 ≤ Ra / Pa ≤ 1.0 (2)

[0015] Furthermore, the method for evaluating cast cold sheet rolling rolls is characterized in that the cast cold sheet rolling roll to be evaluated further contains at least one selected from the group consisting of 2.0% by mass or less of Nb, 5.0% by mass or less of Co, 0.5% by mass or less of Ti, 0.5% by mass or less of Al, and 0.1% by mass or less of Zr.

[0016] Furthermore, the present invention relates to a method for grinding cast rolls for cold rolling, in which an inner layer made of an iron-based alloy is welded and integrated with an outer layer made of an Fe-based alloy having a chemical composition by mass of C: 1.2~2.8%, Si: 0.3~1.2%, Mn: 0.3~1.5%, Ni: 4.0% or less, Cr: 4.0~12.0%, Mo: 0.5~9.0%, V: 3.0~10.0%, W: 0.01~10.0%, and N: 0.01~0.1%, with the remainder being Fe and impurities, and in the finish grinding, the abrasive grain size is JIS This is a grinding method for cast cold-rolled metal rolls, characterized by using a cBN grinding wheel of R6001 with a grit size of #60 to #600 and a volume ratio of abrasive grains to the grinding wheel of 10 to 30%, setting the feed rate of the grinding wheel to 0.1 to 0.5 times the width of the grinding wheel, the depth of cut to 0.005 to 0.33 times the average abrasive grain size, and adjusting the arithmetic mean height Ra of the roughness curve of the outer layer surface and the arithmetic mean height Pa of the cross-sectional curve to satisfy equations (1) and (2).

[0017] The method for grinding cast cold-rolled metal sheets is characterized in that the cast cold-rolled metal sheets to be ground further contain at least one selected from the group consisting of 2.0% by mass or less of Nb, 5.0% by mass or less of Co, 0.5% by mass or less of Ti, 0.5% by mass or less of Al, and 0.1% by mass or less of Zr. [Effects of the Invention]

[0018] By providing a grinding method for high-wear-resistant cast iron rolls for cold sheet rolling that have a surface roughness and homogeneity suitable for cold sheet rolling, it becomes possible to apply high-wear-resistant cast iron rolls, which were difficult to grind due to their high hard carbide content, to cold rolling. This reduces the number of times the rolling mill is stopped due to roll changes in cold rolling and reduces the grinding time required for the rolls. [Modes for carrying out the invention]

[0019] Embodiments of the present invention will be described in detail below, but the present invention is not limited thereto, and various modifications may be made without departing from the technical spirit of the present invention.

[0020] [1] Roll outer layer composition The roll outer layer composition targeted by this application contains, by mass basis, C: 1.2 to 2.8%, Si: 0.3 to 1.2%, Mn: 0.3 to 1.5%, Ni: 4.0% or less, Cr: 4.0 to 12.0%, Mo: 0.5 to 9.0%, V: 3.0 to 10.0%, W: 0.01 to 10.0% and N: 0.01 to 0.1%, and the balance consists of Fe and impurities, and is made of an Fe-based alloy having such a chemical composition.

[0021] (1) Essential elements (a) C: 1.2 to 2.8 mass% C is necessary for the formation of hard carbides for improving wear resistance and for the improvement of the matrix hardness during quenching and tempering by solid solution in the matrix. C forms hard carbides such as MC, M2C, M6C, M7C3, M 23 C6 (where M represents a metal element). If C is less than 1.2 mass%, the amount of hard carbide crystals effective for improving wear resistance is small, and furthermore, the C dissolved in the matrix is insufficient, and sufficient matrix hardness cannot be obtained even by quenching. On the other hand, if it exceeds 2.8 mass%, the hard carbides become coarse and the amount of their crystallization also becomes excessive, and the mechanical properties required for a cold rolling roll cannot be obtained.

[0022] (b) Si: 0.3 to 1.2 mass% Si reduces harmful non-metallic inclusions by deoxidizing the molten metal, improves seizure resistance by dissolving in the matrix, and further has the effect of improving the fluidity of the molten metal to prevent casting defects. If Si is less than 0.3 mass%, the deoxidation effect of the molten metal is insufficient, the fluidity of the molten metal is also insufficient, and the defect occurrence rate is high. On the other hand, if Si exceeds 1.2 mass%, the alloy matrix becomes brittle and the toughness of the outer layer decreases.

[0023] (c) Mn: 0.3 to 1.5 mass% In addition to the deoxidation effect of the molten metal, Mn has the effect of fixing the impurity S as MnS. If Mn is less than 0.3 mass%, the addition effect is insufficient. On the other hand, even if Mn exceeds 1.5 mass%, no further effect can be obtained.

[0024] (d) Ni: 4.0 mass% or less Ni has the effect of improving hardenability and increasing hardness. However, if it exceeds 4.0 mass%, retained austenite becomes excessive, and conversely, high hardness cannot be obtained.

[0025] (e)Cr:4.0~12.0% by mass Cr combines with C to crystallize and form carbides, and also dissolves in the matrix, increasing its hardness and improving wear resistance. This effect is small when the Cr content is less than 4.0 mass%. Furthermore, when it exceeds 12.0 mass%, the amount of carbon in the matrix decreases, making it difficult to achieve sufficient hardness.

[0026] (f)Mo:0.5~9.0% by mass Mo combines with C to form hard carbides (M6C, M2C), increasing the hardness of the outer layer and improving the hardenability of the base material. Furthermore, Mo dissolves into the hard MC carbides, increasing their content and thus improving wear resistance. These effects are insufficient when Mo is less than 0.5 mass%. On the other hand, if Mo exceeds 9.0 mass%, excessive crystallization of carbides occurs, reducing the toughness of the outer layer.

[0027] (g)V:3.0~10.0% by mass V is an element that combines with C to form hard MC carbides. MC carbides have a Vickers hardness of 2500-3000 (HV), making them the hardest of the carbides and significantly affecting the wear resistance of the rolls. If V is less than 3.0 mass%, its additive effect is insufficient. On the other hand, if V exceeds 10.0 mass%, the MC carbides formed in the primary crystal tend to segregate, making surface roughness due to uneven wear during rolling more likely. In addition, oxidation of the molten metal during manufacturing becomes more severe, and the increased viscosity makes it easier for foreign matter such as oxides to get embedded, making it difficult to obtain sound castings.

[0028] (h)W:0.01~10.0% by mass W combines with C to form hard carbides such as M6C and M2C, contributing to improved wear resistance of the outer layer. It also dissolves in MC carbides, increasing their specific gravity and amount, thereby improving wear resistance. However, if the amount of W exceeds 10.0% by mass, the amount of M6C carbides increases, leading to a heterogeneous structure and causing roughness.

[0029] (i)N:0.01~0.1% by mass While nitrogen (N) has the effect of refining carbides, exceeding 0.1% by mass causes the outer layer to become brittle. To obtain a sufficient carbide refining effect, the lower limit of the N content is preferably 0.01% by mass.

[0030] (2) Any element The outer layer may further contain at least one selected from the group consisting of 2.0 mass% or less of Nb, 5.0 mass% or less of Co, 0.5 mass% or less of Ti, 0.5 mass% or less of Al, and 0.1 mass% or less of Zr.

[0031] (a)Nb: 2.0% by mass or less Similar to V, Nb also combines with C to form hard MC carbides. When added in combination with V and Mo, Nb solid-solves in the MC carbides, strengthening them and improving the wear resistance of the outer layer. If the Nb content exceeds 2.0% by mass, oxidation of the molten metal becomes severe, making it difficult to obtain a sound outer layer.

[0032] (b)Co: 5.0% by mass or less Co is an effective element for strengthening the matrix structure, but exceeding 5.0 mass% reduces the toughness of the outer layer.

[0033] (c)Ti: 0.5% by mass or less Ti combines with N and O in the molten metal to form oxynitrides. These are suspended in the molten metal, acting as nuclei, which refine and homogenize the MC carbides. However, if the Ti content exceeds 0.5 mass%, the viscosity of the molten metal increases, making casting defects more likely.

[0034] (d) Al: 0.5% by mass or less Al combines with N and O in the molten metal to form oxynitrides. By reducing the amount of O in the molten metal, oxidation of carbide-forming elements such as V and Cr, which are effective in improving wear resistance, can be prevented. In addition, the formed oxynitrides are suspended in the molten metal and act as nuclei, refining and homogenizing the MC carbides. However, if the Al content exceeds 0.5 mass%, the outer layer becomes brittle, leading to a deterioration of mechanical properties.

[0035] (e) Zr: 0.1% by mass or less Zr combines with carbon to form MC carbides, improving wear resistance. Furthermore, Zr forms oxides in the molten metal, and these oxides act as crystal nuclei, resulting in a finer solidification structure. Additionally, Zr increases the specific gravity of MC carbides, effectively preventing segregation. However, if the Zr content exceeds 0.1% by mass, it becomes an inclusion, which is undesirable.

[0036] (3) Impurities The remainder of the outer layer composition consists of Fe and impurities. P, S, Cu, REM, etc. are impurity elements and trace amounts are unavoidable, but since P forms low-melting-point compounds, its content must be kept to a predetermined level. Also, since P and S cause deterioration of mechanical properties, their content must be kept to a predetermined level. Cu also affects the strength at high temperatures, but its impact is small in trace amounts. Other unavoidable impurities include elements such as Ca, Ba, B, Mg, Sb, Te, and Ce. Specifically, the content of P and S is acceptable if it is less than 0.1 mass%, Cu is less than 0.1 mass%, Ca, Ba, and B are less than 0.05 mass%, Mg is less than 0.07 mass%, Sb is less than 0.05 mass%, and Te and Ce are less than 0.03 mass%.

[0037] [2] Surface skin evaluation index The surface texture evaluation index of the present invention will be described below. The arithmetic mean height Ra of the roughness curve and the arithmetic mean height Pa of the cross-sectional curve used herein are parameters defined in JIS B 0601 2013.

[0038] (1) Ra (arithmetic mean height of the roughness curve): 0.20~1.0 μm The surface roughness Ra of a cold sheet rolling roll is evaluated between 0.20 μm and 1.0 μm. If the surface roughness Ra of a cold sheet rolling roll is less than 0.20 μm, the coefficient of friction between the roll and the material being rolled during cold rolling is too low, which can cause slippage and result in slip damage to the material being rolled, making it unsuitable for use as a cold rolling roll. On the other hand, if Ra exceeds 1.0 μm, the coefficient of friction becomes too high, increasing the rolling load. When rolling thin sheets, this exceeds equipment constraints and limits the thinning of the sheet, making it unsuitable for use as a cold rolling roll. A surface roughness Ra of 0.3 μm to 0.8 μm is preferable for a cold sheet rolling roll.

[0039] (2) Ra / Pa (Arithmetic mean height ratio): 0.65~1.0 The arithmetic mean height ratio (Ra / Pa) of cold sheet rolling rolls is evaluated as being between 0.65 and 1.0. If there are feed marks on the ground surface, the Pa value calculated from the cross-sectional curve will be significantly larger than the Ra value calculated from the roughness curve due to the influence of these undulations. However, when measuring Ra and Pa, it is necessary to make the measurement width wider than the feed width per rotation of the grinding wheel roll during finish grinding, preferably 1.5 times or more. The closer Ra / Pa is to 1, the fewer feed marks there are on the surface, indicating a good surface finish. Specifically, an Ra / Pa value between 0.65 and 1.0 allows for control over achieving a good ground surface for cold rolling without feed marks. An Ra / Pa value between 0.75 and 1.0 is more preferable.

[0040] [3] Surface finishing grinding method By grinding cast cold-rolling rolls using cBN grinding wheels, not only is a stable surface roughness achieved, but a high grinding ratio is also possible, enabling efficient grinding. To achieve a surface finish that satisfies the requirements of 0.20 μm ≤ Ra ≤ 1.0 μm and 0.65 ≤ Ra / Pa ≤ 1.0 for use in cold sheet rolling, it is extremely important to perform appropriate grinding during the finish grinding process. The grinding method for this finish grinding is described below.

[0041] (1) Sharpening stone The following types of cBN grinding wheels are preferable for grinding. While there are various types of binder phases, such as resinoid and vitrified, grinding wheels with any binder phase may be used.

[0042] (a) Abrasive particle size: #60~#600 Depending on the target roll surface roughness, the abrasive grain size should preferably be between #60 and #600 according to JIS R6001, more preferably between #60 and #500, and most preferably between #60 and #360. The specific grain size should be selected appropriately depending on the target surface roughness. For example, to obtain Ra: 0.3 to 0.4 μm, a grain size of around #140 to #320 is desirable.

[0043] (b) Abrasive volume ratio: 10%~30% The volume ratio of cBN abrasive grains to the grinding wheel is preferably 10-30%, and more preferably 10-25%. By applying such abrasive grain volume ratio to the grinding wheel, truing and dressing of the grinding wheel are performed during processing, eliminating the need for dressing and truing by a rotary dresser, which is normally required. If the abrasive grain volume ratio to the grinding wheel is too low during roll processing, the grinding wheel will wear down excessively, and if it is too high, it will cause grinding burn and chatter, and there will be no dressing or truing action of the grinding wheel during processing, requiring separate dressing and truing work.

[0044] (c) Grinding wheel width: 20mm~100mm Increasing the grinding wheel width allows for a higher feed rate, improving efficiency. However, it also increases the contact area with the roll, leading to a rise in the temperature of the grinding surface, which reduces dimensional accuracy. If the temperature continues to rise, it can cause grinding burn. Decreasing the grinding wheel width reduces processing efficiency. A grinding wheel width of 20mm to 100mm is desirable, 25mm to 50mm is more desirable, and 30mm to 35mm is most desirable.

[0045] (2) Grinding conditions during finish grinding (a) Depth of cut: 0.005 to 0.33 times the average abrasive grain size. If the depth of cut exceeds 0.33 times the average abrasive grain size, the load on the abrasive grains during grinding increases, causing grinding burn. Increased load makes the abrasive grains more likely to fall off, accelerating wear of the grinding wheel. Furthermore, the falling off of abrasive grains deforms the shape of the grinding wheel, leading to a deterioration in grinding dimensional accuracy and causing feed marks. A depth of cut of 0.2 times or less the average abrasive grain size of the grinding wheel is more preferable. To eliminate the influence of the surface texture before finish grinding, a depth of cut of 0.005 times or more, preferably 0.01 times or more, the average abrasive grain size of the grinding wheel is required.

[0046] (b) Feed rate: 0.1 to 0.5 times the width of the grinding wheel / roll rotation If the feed rate of the grinding wheel per roll rotation exceeds 0.5 times the width of the grinding wheel, feed marks generated at the leading edge in the direction of grinding wheel movement cannot be removed at the rear of the wheel, resulting in feed marks remaining after grinding. It is preferable that the feed rate of the grinding wheel per roll rotation is 0.33 times the width of the grinding wheel or less. On the other hand, if the feed rate of the grinding wheel per roll rotation is less than 0.1 times the width of the grinding wheel, only the leading edge in the direction of grinding wheel movement will wear down, resulting in poor flatness of the grinding surface and making feed marks more likely to occur.

[0047] (c) Peripheral speed ratio: 11~160 If the ratio of the peripheral speed of the grinding wheel to the peripheral speed of the roll is defined as the peripheral speed ratio (grinding wheel peripheral speed / roll peripheral speed), then if the peripheral speed ratio is less than 11, the grinding wheel will wear down significantly, and if it exceeds 160, chatter is more likely to occur. Therefore, the peripheral speed ratio is preferably in the range of 11 to 160, and more preferably in the range of 16 to 150.

[0048] The present invention will be described in more detail by reference to examples, but the present invention is not limited thereto.

[0049] Composite rolls manufactured by continuous overlay casting were produced in two examples and comparative examples. The outer layer was built up on the inner layer, which was made of steel (SCM440), using molten metal with the composition shown in Table 1, and the outer layer was integrally welded to the outer surface of the inner layer. The outer diameter of the inner layer was 370 mm, the outer diameter of the roll was 570 mm, the thickness of the outer layer buildup was 100 mm, and the length of the outer layer buildup was 3000 mm. After overlay casting, softening annealing was performed, rough machining was carried out, then quenching was performed from 1050°C, followed by tempering at 500-530°C to obtain a body hardness of HS88.

[0050] [Table 1]

[0051] After processing the roll into the product shape, the roll body was finished by grinding using the grinding wheels shown in Table 2 and adjusting the peripheral speed ratio to 40-75 under the conditions shown in Table 3. The surface properties of the roll after grinding are shown in Table 3. In Examples 1 to 5 of the present invention, Ra and Ra / Pa were obtained within the range of the present invention, chatter and grinding burn did not occur, and a homogeneous ground surface suitable for cold sheet rolling was obtained. In Comparative Example 1, although Ra and Ra / Pa were within the range of the present invention, chatter occurred. In Comparative Examples 2 and 3, no chatter or grinding burn occurred, but in Comparative Example 2, the surface roughness Ra was too small, and in Comparative Example 3, the surface roughness Ra was too large, so they did not meet the roll surface roughness required for cold rolling. In Comparative Examples 4 and 5, where the depth of cut exceeded 0.33 times the abrasive grain size, and in Comparative Example 6, where the abrasive feed rate per roll revolution was 0.07 times the abrasive width, Ra / Pa was smaller than the lower limit of the present invention in all cases, resulting in clear abrasive feed marks. Furthermore, grinding burn occurred in Comparative Examples 4 and 5. In Comparative Example 7, where the abrasive volume ratio was 35%, Ra and Ra / Pa were within the range of the present invention, but chatter occurred.

[0052] [Table 2]

[0053] Table 3

Claims

1. In a surface grinding method for the body of a cast cold-rolling roll, in which an inner layer made of an iron-based alloy is welded and integrated into an outer layer made of an Fe-based alloy having a chemical composition by mass of C: 1.2-2.8%, Si: 0.3-1.2%, Mn: 0.3-1.5%, Ni: 4.0% or less, Cr: 4.0-12.0%, Mo: 0.5-9.0%, V: 3.0-10.0%, W: 0.01-10.0%, and N: 0.01-0.1%, with the remainder being Fe and impurities, the surface grinding method for the body of a cast cold-rolling roll is in which an inner layer made of an iron-based alloy is welded and integrated into an outer layer made of an Fe-based alloy having a chemical composition by mass of C: 1.2-2.8%, Si: 0.3-1.2%, Mn: 0.3-1.5%, Ni: 4.0% or less, Cr: 4.0-12.0%, Mo: 0.5-9.0%, V: 3.0-10.0%, W: 0.01-10.0%, and N: 0.01-0.1%, with the remainder being Fe and impurities, in the finish grinding, the abrasive grain size is JIS A method for grinding cast cold-rolled sheet metal rolls, characterized by using a cBN grinding wheel of R6001 with a grit size of #60 to #600 and a volume ratio of abrasive grains to grinding wheel of 10 to 30%, setting the feed rate of the grinding wheel to 0.1 to 0.5 times the width of the grinding wheel, the depth of cut to 0.005 to 0.33 times the average abrasive grain size, and adjusting so that the arithmetic mean height Ra of the roughness curve and the arithmetic mean height Pa of the cross-sectional curve of the outer layer surface satisfy equations (1) and (2). 0.20μm≦Ra≦1.0μm (1) 0.65 ≦ Ra / Pa ≦ 1.0 (2)

2. The method for grinding a cast cold rolling roll according to claim 1, characterized in that the outer layer further contains at least one selected from the group consisting of 2.0% by mass or less of Nb, 5.0% by mass or less of Co, 0.5% by mass or less of Ti, 0.5% by mass or less of Al, and 0.1% by mass or less of Zr.

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