A cold rolling working roll and preparation method thereof

Abstract

The invention discloses a cold rolling working roller, comprising a 9Cr5MoV alloy steel substrate and a transition coating and a W6Mo5Cr4V2 alloy steel powder coating sequentially arranged on the surface thereof; the transition coating is a mixed powder coating of 9Cr5MoV and W6Mo5Cr4V2. The preparation method of the cold rolling working roller of the invention comprises: preparation of the transition coating; preparation of the W6Mo5Cr4V2 alloy steel powder coating; cutting processing; quenching; and fine grinding. The invention innovates the material of the working roller and combines the advantages of high-speed laser cladding technology to make the working roller have a long service life, high wear resistance, a short process, and low cost.

Description

Technical Field

[0001] The invention relates to the technical field of cold rolling, and in particular to a cold rolling working roll and a preparation method thereof. Background Art

[0002] The common materials used for cold-rolled stainless steel working rolls are 9Cr5MoV and W6Mo5Cr4V2. 9Cr5MoV material is cheap but not wear-resistant and has a short lifespan; W6Mo5Cr4V2 material is expensive but has a long lifespan and good wear resistance.

[0003] The current production process of working rolls is: selection of raw materials → EBT primary refining → LF refining → vacuum degassing → casting molding → electroslag remelting → forging → spheroidizing annealing → rough machining → quenching and tempering → semi-finishing → flaw detection → preheat treatment → dual-frequency quenching → cold treatment → low-temperature tempering → finishing → hardness, ultrasonic and metallographic → packaging and shipment.

[0004] Stainless steel cold-rolled steel plate is a stainless steel plate produced by cold rolling process. Through different processing methods of cold rolling process and surface reprocessing after cold rolling, the stainless steel surface can have different levels of surface finish, texture and color. Such a rich variety of surfaces greatly improves the appearance of stainless steel, broadens the connotation of stainless steel use, thereby expanding the scope of use of stainless steel, becoming the most widely used structural variety of stainless steel.

[0005] High-speed laser cladding technology is a coating combined with metallurgy of the micro-melting base surface interface by adding metal alloy powder through laser high-energy density cladding. It is a reinforced material manufacturing technology that can greatly improve the surface wear resistance, corrosion resistance and life of parts. High-speed laser cladding obtains more uniform coating thickness, flat surface quality, reduced dilution rate, improved deposition efficiency, small workpiece shape variables, etc. than traditional laser cladding through laser scanning speed. It has become a new field of laser application that domestic and foreign research institutions and enterprises focus on.

[0006] High-speed laser cladding technology can reduce processing costs in the field of laser manufacturing and remanufacturing, improve product quality, and extend product life. It is widely used in industrial applications such as hydraulic struts, shaft parts, large cover molds, valves, etc.

[0007] High-speed laser cladding has a high power density and can clad high-melting-point powder materials. Compared with traditional laser cladding, high-speed laser cladding is green, environmentally friendly and pollution-free. Summary of the invention

[0008] The existing cold-rolled stainless steel working roll material is mostly 9Cr5MoV, which is cheap but not wear-resistant. In addition, W6Mo5Cr4V2 high-speed steel is commonly used, but this material is expensive. By spraying a layer of W6Mo5Cr4V2 material on the original material of the working roll through high-speed laser cladding, the new material has high wear resistance, long service life, and greatly reduced cost. However, the inventor further found that the service life and hardness of the obtained material still need to be further improved by directly spraying W6Mo5Cr4V2 coating directly on the 9Cr5MoV substrate. For this reason, the present invention proposes a technical solution of arranging a transition coating between the 9Cr5MoV substrate and the W6Mo5Cr4V2 coating.

[0009] The present invention uses high-speed laser cladding to sequentially coat a transition coating layer with a thickness of 10-30 μm and a W6Mo5Cr4V2 material layer with a thickness of 10-30 mm on the surface of a 9Cr5MoV working roll, thereby reducing costs while ensuring a long service life and high wear resistance. The complete process flow of the present invention may be: selecting raw materials → EBT primary refining → LF refining → vacuum degassing → casting molding → electroslag remelting → forging → high-speed laser cladding → finishing → hardness, ultrasonic wave and metallographic structure → packaging and delivery.

[0010] Through this invention, the material of the working roll is innovated and combined with the advantages of high-speed laser cladding technology, the working roll has a long life, high wear resistance, short process and low cost.

[0011] A cold rolling working roll comprises a 9Cr5MoV alloy steel substrate and a transition coating and a W6Mo5Cr4V2 alloy steel powder coating sequentially arranged on the surface thereof;

[0012] The transition coating is a mixed powder coating of 9Cr5MoV and W6Mo5Cr4V2.

[0013] Preferably, the volume fraction of W6Mo5Cr4V2 in the mixed powder coating is 50% to 85%, and the rest is 9Cr5MoV.

[0014] Further preferably, the volume fraction of W6Mo5Cr4V2 in the mixed powder coating is 70%, and the rest is 9Cr5MoV.

[0015] Preferably, the thickness of the transition coating is 10-30 μm.

[0016] Preferably, the thickness of the W6Mo5Cr4V2 alloy steel powder coating is 10-30 mm.

[0017] The present invention also provides a method for preparing the cold rolling work roll, comprising the steps of:

[0018] 1) Preparation of transition coating: 9Cr5MoV powder and W6Mo5Cr4V2 powder are ball-milled and vacuum-dried, and then the transition coating is made on the surface of the 9Cr5MoV alloy steel substrate by high-speed laser cladding technology;

[0019] 2) Preparation of W6Mo5Cr4V2 alloy steel powder coating: W6Mo5Cr4V2 powder is used as the spraying material, and the W6Mo5Cr4V2 alloy steel powder coating is made on the surface of the transition coating by adopting high-speed laser cladding technology;

[0020] 3) Cutting process;

[0021] 4) Quenching: adopt graded quenching, the first preheating temperature is 740-750℃, the second preheating temperature is 855-865℃, the final temperature is 1235-1250℃, and then oil cooling is adopted to make the hardness reach 64-66HRC;

[0022] 5) Fine grinding to achieve a surface roughness of 0.7-0.8Ra to obtain the cold rolling working roll.

[0023] The present invention uses two high-speed laser claddings to sequentially form a transition coating and a W6Mo5Cr4V2 coating on the surface of a 9Cr5MoV substrate, and then adopts a quenching process under specific conditions adapted thereto (the first preheating temperature and the second preheating temperature of the quenching process of the present invention are both higher than the conventional first preheating temperature of about 680°C and the second preheating temperature of about 790°C), to finally obtain a cold-rolled working roll with a long life and high hardness.

[0024] In step 1), the 9Cr5MoV powder is preferably prepared by a gas atomization method.

[0025] In step 1), the particle size of the W6Mo5Cr4V2 powder is preferably 100-200 mesh.

[0026] In step 1), preferably, the ball milling method is intermittent ball milling, the total ball milling time is 14 hours, and the ball milling speed is 400 rpm.

[0027] In step 1), preferably, the vacuum drying temperature is 65° C. and the time is 15 h.

[0028] In step 1), preferably, the parameter conditions of the high-speed laser cladding technology include: laser power of 2.5-3.5KW, spot area of ​​10mm×2mm, powder feeding rate of 14-22g / min, shielding gas flow rate of 8-13L / min, laser scanning rate of 10-35m / min, overlap rate of 35%-50%, and shielding gas of argon.

[0029] In step 2), preferably, the parameter conditions of the high-speed laser cladding technology include: laser power of 2.5-3.5KW, spot area of ​​10mm×2mm, powder feeding rate of 14-22g / min, shielding gas flow rate of 8-13L / min, laser scanning rate of 10-35m / min, overlap rate of 35%-50%, and shielding gas of argon.

[0030] In step 3), a CA9140 lathe can be used for cutting, with a turning depth of 3-5 mm, a high-speed steel tool, a speed v of 24-27 m / min, and a rotation speed f of 0.35-0.45 mm / r.

[0031] In step 4), the first preheating time is preferably 20-30 s / mm effective thickness, the second preheating time is preferably 15-25 s / mm effective thickness, and the final temperature dwell time is preferably 12-20 s / mm effective thickness.

[0032] In step 5), preferably, the fine grinding uses a steel roller, the abrasive uses white corundum (WA), the particle size is 60-80 mesh, the hardness grade is H, and the binder is V.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The present invention makes the bonding force between the 9Cr5MoV substrate and the W6Mo5Cr4V2 coating stronger through the design of the transition coating, and the ultimately obtained cold rolling working roll has a longer service life and a higher hardness. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic structural diagram of the cold rolling working roll of the present invention, in which: 1-W6Mo5Cr4V2 alloy steel powder coating; 2-transition coating; 3-9Cr5MoV alloy steel substrate. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the accompanying drawings and specific examples. It should be understood that these examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention. The operating methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturer.

[0037] like Figure 1 As shown, the cold rolling working roller of the present invention comprises a 9Cr5MoV alloy steel substrate 3 and a transition coating 2 and a W6Mo5Cr4V2 alloy steel powder coating 1 sequentially arranged on the surface thereof; the transition coating 2 is a mixed powder coating of 9Cr5MoV and W6Mo5Cr4V2.

[0038] The service life of the cold rolling work roll made of a single material of 9Cr5MoV alloy steel matrix is ​​10 months and the hardness is 55HRC.

[0039] Example 1

[0040] The experiments were carried out using W6Mo5Cr4V2 powder.

[0041] In the first step, the laser power used was 3KW, the spot area was 10mm×2mm, the powder feeding rate was 15g / min, the protective gas argon flow rate was 10L / min, the laser scanning rate was 20m / min, and the overlap rate was 40%.

[0042] In the second step, a CA9140 lathe is used for cutting. The cutting depth is 4mm, a high-speed steel tool is used, the speed v is 25m / min, and the rotation speed f is 0.4mm / r.

[0043] The third step is to use graded quenching. The first preheating temperature is 740℃ for 25s / mm, the second preheating temperature is 860℃ for 22s / mm, and the final temperature is 1240℃ for 15s / mm. Oil cooling is used.

[0044] The fourth step is to use steel roller fine grinding, using WA as abrasive, 60-80 mesh, H as hardness grade, and V as bonding agent to achieve a surface roughness of 0.7Ra, and obtain a cold rolling working roller with a service life of 12 months and a hardness of 64HRC.

[0045] Example 2

[0046] A transition coating, i.e., a mixture of 9Cr5MoV and W6Mo5Cr4V2, was used as the transition coating, wherein the volume fraction of 9Cr5MoV powder was 50% and the volume fraction of W6Mo5Cr4V2 powder was 50%. Then, the W6Mo5Cr4V2 powder was used for the experiment.

[0047] In the first step, 9Cr5MoV and W6Mo5Cr4V2 powders are used as raw materials, and pure 9Cr5MoV alloy powder is prepared by gas atomization method, and W6Mo5Cr4V2 powder of tungsten-molybdenum high-speed steel is added, with a particle size of 100-200 mesh. The two powders are poured into a ball mill, intermittently ball milled on the ball mill for 14 hours at a speed of 400r / min, and placed in a vacuum drying oven at 65℃ for 15 hours for drying after being fully mixed. The laser power used is 3KW, the spot area is 10mm×2mm, the powder feeding rate is 15g / min, the protective gas argon flow rate is 10L / min, the laser scanning rate is 20m / min, the overlap rate is 40%, and the coating thickness is 20μm.

[0048] In the second step, the laser power used is 3KW, the spot area is 10mm×2mm, the powder feeding rate is 15g / min, the protective gas argon flow rate is 10L / min, the laser scanning rate is 20m / min, the overlap rate is 40%, and the coating thickness is 20mm.

[0049] The third step is cutting: use CA9140 lathe for cutting, use turning processing back cutting depth of 4mm, use high-speed steel tools, speed v is 25m / min, and rotation speed f is 0.4mm / r.

[0050] The fourth step is to use graded quenching. The first preheating temperature is 740℃ and the time is 25s / mm. The second preheating temperature is 860℃ and the time is 22s / mm. The final temperature is 1240℃ and the time is 15s / mm. Oil cooling is used.

[0051] The fifth step is to use steel roller fine grinding, using WA as abrasive, 60-80 mesh, H as hardness grade, and V as bonding agent to achieve a surface roughness of 0.7Ra, and obtain a cold rolling working roller with a service life of 13 months and a hardness of 65HRC.

[0052] Example 3

[0053] The only difference from Example 2 is that the volume fraction of 9Cr5MoV powder in the transition coating is 15%, and the volume fraction of W6Mo5Cr4V2 powder is 85%, and the rest are the same. The resulting cold rolling working roll has a service life of 13 months and a hardness of 66HRC.

[0054] Example 4

[0055] The only difference from Example 2 is that the volume fraction of 9Cr5MoV powder in the transition coating is 30%, and the volume fraction of W6Mo5Cr4V2 powder is 70%, and the rest are the same. The resulting cold rolling working roll has a service life of 15 months and a hardness of 66HRC.

[0056] From the above examples, we can clearly see that:

[0057] 1) The addition of coating significantly increases the life of the material and significantly improves its hardness.

[0058] 2) The addition of transition coating makes the spraying effect better, further increases the service life and increases the hardness, so the transition coating plays a vital role.

[0059] 3) Comparing the composition of transition coating, it is found that the best effect is achieved when 30vol% 9Cr5MoV and 70vol% W6Mo5Cr4V2 powders are mixed. It has a longer life and greater hardness than 50vol% 9Cr5MoV and 50vol% W6Mo5Cr4V2. It has the same hardness as 15vol% 9Cr5MoV and 85vol% W6Mo5Cr4V2, but a longer life.

[0060] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A cold rolling work roll, characterized in that: It includes a 9Cr5MoV alloy steel substrate and a transition coating and a W6Mo5Cr4V2 alloy steel powder coating sequentially arranged on the surface thereof; The transition coating is a mixed powder coating of 9Cr5MoV and W6Mo5Cr4V2; The volume fraction of W6Mo5Cr4V2 in the mixed powder coating is 70%, and the rest is 9Cr5MoV; The thickness of the transition coating is 10-30 μm; The thickness of the W6Mo5Cr4V2 alloy steel powder coating is 10-30 mm; The method for preparing the cold rolling work roll comprises the steps of: 1) Preparation of transition coating: 9Cr5MoV powder and W6Mo5Cr4V2 powder are ball-milled and vacuum-dried, and then the transition coating is made on the surface of the 9Cr5MoV alloy steel substrate by high-speed laser cladding technology; 2) Preparation of W6Mo5Cr4V2 alloy steel powder coating: W6Mo5Cr4V2 powder is used as the spraying material, and the W6Mo5Cr4V2 alloy steel powder coating is made on the surface of the transition coating by adopting high-speed laser cladding technology; 3) Cutting process; 4) Quenching: adopt graded quenching, the first preheating temperature is 740-750℃, the second preheating temperature is 855-865℃, the final temperature is 1235-1250℃, and then oil cooling is adopted to make the hardness reach 66HRC; 5) Fine grinding to achieve a surface roughness of 0.7-0.8Ra to obtain the cold rolling working roll.

2. The method for preparing a cold rolling work roll according to claim 1, characterized in that: Includes steps: 1) Preparation of transition coating: 9Cr5MoV powder and W6Mo5Cr4V2 powder are ball-milled and vacuum-dried, and then the transition coating is made on the surface of the 9Cr5MoV alloy steel substrate by high-speed laser cladding technology; 2) Preparation of W6Mo5Cr4V2 alloy steel powder coating: W6Mo5Cr4V2 powder is used as the spraying material, and the W6Mo5Cr4V2 alloy steel powder coating is made on the surface of the transition coating by adopting high-speed laser cladding technology; 3) Cutting process; 4) Quenching: adopt graded quenching, the first preheating temperature is 740-750℃, the second preheating temperature is 855-865℃, the final temperature is 1235-1250℃, and then oil cooling is adopted to make the hardness reach 64-66HRC; 5) Fine grinding to achieve a surface roughness of 0.7-0.8Ra to obtain the cold rolling working roll.

3. The preparation method according to claim 2, characterized in that: In step 1): The 9Cr5MoV powder is prepared by gas atomization; The particle size of the W6Mo5Cr4V2 powder is 100-200 mesh; The ball milling method is intermittent ball milling, the total ball milling time is 14 hours, and the ball milling speed is 400 rpm; The vacuum drying temperature is 65°C and the time is 15h; The parameters of the high-speed laser cladding technology include: laser power of 2.5-3.5KW, spot area of ​​10mm×2mm, powder feeding rate of 14-22g / min, shielding gas flow of 8-13L / min, laser scanning rate of 10-35m / min, overlap rate of 35%-50%, and shielding gas of argon.

4. The preparation method according to claim 2, characterized in that: In step 2), the parameter conditions of the high-speed laser cladding technology include: laser power of 2.5-3.5KW, spot area of ​​10mm×2mm, powder feeding rate of 14-22g / min, shielding gas flow rate of 8-13L / min, laser scanning rate of 10-35m / min, overlap rate of 35%-50%, and shielding gas of argon.

5. The preparation method according to claim 2, characterized in that: In step 3), a CA9140 lathe is used for cutting, a turning depth of 3-5 mm, a high-speed steel tool, a speed v of 24-27 m / min, and a rotation speed f of 0.35-0.45 mm / r are selected.

6. The preparation method according to claim 2, characterized in that: In step 4), the first preheating time is 20-30 s / mm effective thickness, the second preheating time is 15-25 s / mm effective thickness, and the final temperature dwell time is 12-20 s / mm effective thickness.

7. The preparation method according to claim 2, characterized in that: In step 5), the fine grinding uses a steel roller, the abrasive uses white corundum, the particle size is 60-80 mesh, the hardness grade is H, and the bonding agent is V.

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