Inner wall stress control and heat treatment method of high speed steel outer shell of coiler combined roller

Abstract

The invention discloses an inner wall stress control and heat treatment method of a high-speed steel outer jacket of a combined roll of a coiler, comprising the following steps: step S1, pouring an outer layer and an inner wall of a high-alloy roll sleeve, step S2, preheating the high-alloy roll sleeve as a whole, the preheating temperature is 500-700°C, during preheating, the inner hole of the roll sleeve is kept flowing to ensure uniform preheating of the inside and outside, and the temperature difference is ≤15°C; step S3, after sufficient preheating, induction quenching heating the outer circle of the roll sleeve within 20 minutes, rapidly heating during induction quenching heating, the heating rate is 30-50°C / min, and the temperature is kept for 15-25 minutes after heating to a certain temperature; step S4, after the induction quenching and heat preservation are completed, refractory fibers are used to seal the two ends of the high-alloy roll sleeve, and water is sprayed and air is blown on the surface of the high-alloy roll sleeve; step S5, tempering is performed twice at a temperature of 500-550°C and 10-15 hours.

Description

Technical Field

[0001] The invention relates to centrifugal roller manufacturing, in particular to an inner wall stress control and heat treatment method of a high-speed steel outer jacket of a combined roller of a coiler. Background Art

[0002] The pinch rolls of hot rolling coilers used to be made of surfacing materials, but after upgrading, they use high-performance high-alloy jacket combination rolls, which greatly improves the performance. The high-alloy roll jacket is generally made of high-speed steel, which needs to be quenched at high temperature to fully exert its performance. However, the higher the material temperature, the more difficult it is to control the stress of the inner wall after quenching. Excessive stress may cause cracking after interference fitting or cracking and scrapping during use. Therefore, how to control the stress of the inner wall while giving full play to the performance of the outer layer is the difficulty of heat treatment of the combination roll jacket. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for controlling the inner wall stress and heat treating the high-speed steel outer jacket of the combined roller of the coiler. While the surface structure and hardness achieve high performance, the inner wall stress can be stably controlled below 100MPa, and cracking and failure will not occur due to stress superposition during subsequent interference assembly and use.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for controlling the inner wall stress and heat treating the high-speed steel outer jacket of the combined roll of the coiler, comprising the following steps:

[0005] Step S1, casting the outer layer and inner wall of the high alloy roller sleeve, wherein the outer layer is made of high-speed steel with a C mass fraction of 0.9-3.2%, and the inner layer is made of high-carbon graphite steel with a C mass fraction of 1.0%-1.5%;

[0006] Step S2, preheating the high alloy roller sleeve as a whole, the preheating temperature is 500-700°C, the preheating time is 8-18h, and the inner hole of the roller sleeve is kept flowing to ensure uniform preheating inside and outside, and the temperature difference is ≤15°C;

[0007] Step S3, after sufficient preheating, the outer circle of the roller sleeve is induction quenched and heated within 20 minutes, and the temperature is quickly increased during induction quenching heating, with a heating rate of 30-50°C / min, and the temperature is kept for 15-25 minutes after it reaches a certain temperature;

[0008] Step S4: After the induction quenching and heat preservation is completed, both ends of the high alloy roller sleeve are sealed with refractory fibers, and the surface of the high alloy roller sleeve is sprayed with water and blown with air;

[0009] Step S5, performing tempering twice at 500-550° C. for 10-15 hours.

[0010] A further improvement of the technical solution of the present invention is that in step S1, the casting thickness ratio of the outer layer and the inner wall of the high alloy roller sleeve is less than 1.0.

[0011] A further improvement of the technical solution of the present invention is that during the induction quenching heating in step S3, the power frequency is 50-100 Hz when the thickness of the outer layer is ≤20 mm, and the power frequency is 100-150 Hz when the thickness of the outer layer is 20-40 mm.

[0012] A further improvement of the technical solution of the present invention is that in step S3, when the outer layer C≤1.5%, the quenching temperature is 1030-1050°C, when the outer layer is 1.5%<C<2.5%, the quenching temperature is 1010-1030°C, and when the outer layer is 2.5%<C<3.2%, the quenching temperature is 990-1010°C.

[0013] A further improvement of the technical solution of the present invention is that: in step S4, the surface of the high alloy roller sleeve is sprayed with water to 550°C, and then the surface of the high alloy roller sleeve is blown to prevent temperature reversal, and the blowing is stopped after the temperature drops to 540°C, and finally the high alloy roller sleeve continues to slowly cool to 400-450°C.

[0014] A further improvement of the technical solution of the present invention is that the cooling rate of spraying water on the surface of the high alloy roller sleeve in step S4 reaches above 10°C / min.

[0015] A further improvement of the technical solution of the present invention is that in step S5, when the outer layer hardness of the high alloy roller sleeve is required to be 70-80HS, the tempering temperature is 530-550°C; when the outer layer hardness of the high alloy roller sleeve is required to be 80-90HS, the tempering temperature is 500-530°C.

[0016] A further improvement of the technical solution of the present invention is that: in step S5, when the wall thickness of the high alloy roller sleeve is ≤100 mm, the tempering time is 10-12 hours; when the wall thickness of the high alloy roller sleeve is in the range of 100-180 mm, the tempering time is 12-15 hours.

[0017] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is:

[0018] 1. The outer shell of the high-speed steel pinch roller produced by the present invention has a high surface structure and hardness, while the inner wall stress can be stably controlled below 100MPa, and will not crack and fail due to stress superposition during subsequent interference assembly and use;

[0019] 2. In the present invention, the outer wall of the roller sleeve is made of high-speed steel, which can reach a high hardness after heat treatment to ensure wear resistance. The inner layer is made of low-alloy steel to maintain good toughness to avoid failure during heat treatment and equipment use. The high-alloy roller sleeve is preheated at 500-700°C to relax the casting stress and allow the roller sleeve to enter the plastic temperature range, so that it is not easy to crack during the quenching process. After the roller sleeve is preheated, it is necessary to start heating quickly to ensure the preheating effect. At the same time, the temperature is quickly raised and the heat is kept for a short time to ensure that the outer wall achieves the quenching effect while the inner wall is not overheated to maintain toughness. Then, the surface of the high-alloy roller sleeve is sprayed with water and air to quickly cool down and quench, and the two ends are blocked to ensure that the inner wall is not chilled and toughness is guaranteed. Finally, through multiple high-temperature tempering, the quenched austenite is fully transformed into tempered martensite, and tempering hardening ensures performance while reducing the stress of the inner hole. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below in conjunction with embodiments:

[0021] The present invention is suitable for a pinch roller sleeve made of high-speed steel, the outer layer (usage layer) has a chemical composition mass fraction of C: 0.9-3.2%, Σ(Cr+Mo+V+W)≥8%, and Ni%≥1.0% of the high-speed steel material, the outer diameter of the roller sleeve is generally 600-1100mm, and the length is 600-3000mm. After heat treatment of the roller sleeve, the usage layer structure is tempered martensite + carbide, and the hardness of the usage layer is 70-90HS.

[0022] Centrifugal composite casting is used during casting. The outer layer (use layer) is made of high-speed steel, the inner wall is made of high-carbon graphite steel with a C mass fraction of 1.0-1.5%, and the outer wall of the roller sleeve is made of high-speed steel. After heat treatment, it can reach a higher hardness to ensure wear resistance. The inner layer is made of low-alloy steel to maintain good toughness and avoid failure during heat treatment and equipment use.

[0023] The inner wall stress control and heat treatment method of the high-speed steel outer jacket of the coiler combination roller includes the following steps:

[0024] Step S1, casting the outer layer and inner wall of the high alloy roller sleeve. Since the inner wall needs to have a certain thickness to ensure that the strength is not affected by the outer layer, the casting thickness ratio of the outer layer and the inner wall of the high alloy roller sleeve is less than 1.0;

[0025] Step S2, preheating the high alloy roller sleeve as a whole, the preheating temperature is 500-700℃, the preheating time is 8-18h, during preheating, the inner hole of the roller sleeve is kept flowing to ensure uniform preheating inside and outside, and the temperature difference is ≤15℃; preheating the roller sleeve at 500-700℃ can relax the casting stress and make the roller sleeve enter the plastic temperature range, and it is not easy to crack during the quenching process. If the preheating temperature is too low, there will be no effect, and if the preheating temperature is too high, the inner wall is easy to be quenched, affecting the performance.

[0026] Step S3, after sufficient preheating, quickly heat the outer circle of the roller sleeve by induction quenching within 20 minutes to ensure the effect of step S2, and at the same time quickly heat up and keep warm for a short time to ensure that the outer wall achieves the quenching effect while the inner wall is not overheated and maintains toughness. When induction quenching heating, when the thickness of the outer layer is ≤20mm, the power frequency is 50-100Hz; when the thickness of the outer layer is 20-40mm, the power frequency is 100-150Hz. Rapidly heat up during induction quenching heating, with a heating rate of 30-50℃ / min. If the roller sleeve heats up slowly after preheating, the inner wall is easily quenched and affects the performance. When the outer layer C≤1.5%, the quenching temperature is 1030-1050℃, and the outer layer 1.5%<C≤2.5%, the quenching temperature is 1010-1030℃, and the outer layer 2.5%<C≤3.2%, the quenching temperature is 990-1010℃. Quenching and heat preservation time is 15-25min;

[0027] Step S4: After the induction quenching and heat preservation is completed, the two ends of the high alloy roller sleeve are sealed with refractory fibers, and the surface of the high alloy roller sleeve is sprayed with water to 550°C, and the cooling rate of the water spraying reaches more than 10°C / min. Avoid the pearlite structure on the outer layer, and then blow air to the surface of the high alloy roller sleeve to prevent temperature reversal until the temperature drops to 540°C and then stop blowing. Finally, the high alloy roller sleeve continues to slowly cool to 400-450°C. If it is directly cooled to 400-450°C by blowing, the greater the subsequent cooling intensity, the greater the stress and failure risk.

[0028] Step S5, perform two temperings at 500-550℃ for 10-15h. Since the martensitic transformation termination temperature is lower than room temperature, one tempering cannot ensure sufficient transformation. Generally, the second tempering is performed after the first tempering drops to room temperature. When the outer layer hardness of the high alloy roller sleeve is required to be 70-80HS, the tempering temperature is 530-550℃; when the outer layer hardness of the high alloy roller sleeve is required to be 80-90HS, the tempering temperature is 500-530℃. When the wall thickness of the high alloy roller sleeve is ≤100mm, the tempering time is 10-12h; when the wall thickness of the high alloy roller sleeve is in the range of 100-180mm, the tempering time is 12-15h.

[0029] Embodiment 1:

[0030] A high-speed steel pinch roller sleeve with an outer layer C mass fraction of 0.9-1.5%, an outer diameter of 960mm, an inner cavity diameter of 750mm, a working layer of 25mm, and a hardness requirement of 75-80HS.

[0031] Centrifugal composite casting is used, the inner wall is made of graphite steel, the C mass fraction is 1.0%, the outer layer casting thickness is 37mm, the inner wall casting thickness is 77mm, and the thickness ratio of the outer layer to the inner wall is 0.48.

[0032] The high alloy roller sleeve is preheated as a whole, and the furnace temperature is set at 650℃. During preheating, the inner hole of the roller sleeve is kept flowing. After preheating for 8 hours, the inner wall temperature is 620℃ and the outer wall temperature is 630℃.

[0033] After preheating out of the furnace, induction quenching heating begins 10 minutes later, the power frequency is 120Hz, the heating rate is 40℃ / min, the quenching temperature is 1050℃, and the temperature is kept for 20 minutes.

[0034] After the induction quenching and heat preservation is completed, the two ends of the roller sleeve are sealed with refractory fibers. Spray water on the roller sleeve surface for the first 10 minutes, and the temperature of the high alloy roller sleeve outer layer drops to 550℃. The surface cooling rate reaches 15℃ / min. Blow air on the surface for the next 20 minutes to prevent temperature reversal. Stop blowing air after the temperature drops to 540℃. After 540℃, let it air naturally to 440℃ before loading and tempering in the furnace. The first tempering is 530℃×13h, and the second tempering is 540℃×13h.

[0035] After heat treatment, the outer wall hardness test was 77-80HSD, the structure was tempered martensite + 10% carbide; the inner hole stress was tested by blind hole method and the tensile stress was 86MPa. After processing to the finished product interference fit, it was normal without cracking, and it was normal for continuous use in the machine for 3 months.

[0036] Embodiment 2:

[0037] A C2.5-3.2 high-speed steel pinch roller sleeve with an outer diameter of 920mm, an inner diameter of 690mm, a working layer of 15mm, and a hardness requirement of 80-85HS.

[0038] Centrifugal composite casting is used, the inner wall is made of graphite steel, the actual C mass fraction is 1.5%, the outer layer casting thickness is 25mm, the inner wall casting thickness is 90mm, and the thickness ratio of the outer layer to the inner wall is 0.28.

[0039] The high alloy roller sleeve is preheated as a whole, and the furnace temperature is set at 700℃. During preheating, the inner hole of the roller sleeve is kept flowing. After preheating for 10 hours, the inner wall temperature is 660℃ and the outer wall temperature is 680℃.

[0040] After preheating out of the furnace, induction quenching heating begins 10 minutes later, the power frequency is 100Hz, the heating rate is 50℃ / min, the quenching temperature is 1000℃, and the heat preservation time is 15 minutes.

[0041] After the induction quenching and heat preservation is completed, the two ends of the roller sleeve are sealed with refractory fibers. Spray water on the roller sleeve surface for the first 12 minutes, and the temperature of the high alloy roller sleeve outer layer drops to 550℃. The surface cooling rate reaches 15℃ / min. Blow air on the surface for the next 18 minutes to prevent temperature reversal. Stop blowing air after the temperature drops to 540℃. After 540℃, let it air naturally to 440℃ before loading and tempering in the furnace. The first tempering is 540℃×14h, and the second tempering is 550℃×14h.

[0042] After the heat treatment, the outer wall hardness test was 83-84HSD, the structure was tempered martensite + 18% carbide; the inner hole stress was tested by blind hole method and the tensile stress was 91MPa. After the finished product was processed and fitted with interference fit, it was normal without cracking, and it was normal after continuous use in the machine for 3 months.

[0043] Embodiment 3:

[0044] A C1.6-2.4 high-speed steel pinch roller sleeve with an outer diameter of 910mm, an inner diameter of 630mm, a working layer of 40mm, and a hardness requirement of 78-83HS.

[0045] Centrifugal composite casting is used, the inner wall is made of graphite steel, the actual C mass fraction is 1.22%, the outer layer casting thickness is 45mm, the inner wall casting thickness is 95mm, and the thickness ratio of the outer layer to the inner wall is 0.47.

[0046] The high alloy roller sleeve is preheated as a whole, and the furnace temperature is set at 680℃. During preheating, the inner hole of the roller sleeve is kept flowing. After preheating for 15 hours, the inner wall temperature is 640℃ and the outer wall temperature is 660℃.

[0047] After preheating out of the furnace, induction quenching heating begins 10 minutes later, the power frequency is 150Hz, the heating rate is 30℃ / min, the quenching temperature is 1020℃, and the temperature is kept for 25 minutes.

[0048] After the induction quenching and heat preservation is completed, the two ends of the roller sleeve are sealed with refractory fibers. Spray water on the roller sleeve surface for the first 15 minutes, and the temperature of the high alloy roller sleeve outer layer drops to 550℃. The surface cooling rate reaches 15℃ / min. Blow air on the surface for the next 20 minutes to prevent temperature reversal. Stop blowing air after the temperature drops to 540℃. After 540℃, let it air naturally to 440℃ before loading and tempering in the furnace. The first tempering is 535℃×15h, and the second tempering is 545℃×15h.

[0049] After the heat treatment, the outer wall hardness test was 80-83HSD, the structure was tempered martensite + 15% carbide; the inner hole stress was tested by blind hole method and the tensile stress was 92MPa. After the finished product was processed and fitted with interference fit, it was normal without cracking, and it was normal after continuous use in the machine for 3 months.

Claims

1. The inner wall stress control and heat treatment method of the high-speed steel outer jacket of the coiler combination roller is characterized by: The steps include: Step S1, casting the outer layer and inner wall of the high alloy roller sleeve, wherein the outer layer is made of high-speed steel with a C mass fraction of 0.9-3.2%, and the inner layer is made of high-carbon graphite steel with a C mass fraction of 1.0%-1.5%; Step S2, preheating the high alloy roller sleeve as a whole, the preheating temperature is 500-700°C, the preheating time is 8-18h, during preheating, the inner hole of the roller sleeve is kept flowing to ensure uniform preheating inside and outside, and the temperature difference is ≤15°C; Step S3, after sufficient preheating, the outer circle of the roller sleeve is induction quenched and heated within 20 minutes. When the outer layer C≤1.5%, the quenching temperature is 1030-1050℃, when the outer layer is 1.5%<C<2.5%, the quenching temperature is 1010-1030℃, when the outer layer is 2.5%<C<3.2%, the quenching temperature is 990-1010℃, when the outer layer thickness is ≤20mm, the power frequency is 50-100Hz; when the outer layer thickness is 20-40mm, the power frequency is 100-150Hz, the temperature is quickly increased during induction quenching heating, the heating rate is 30-50℃ / min, and the temperature is kept for 15-25min after heating to a certain temperature; Step S4, after the induction quenching and heat preservation is completed, the two ends of the high alloy roller sleeve are sealed with refractory fibers, and the surface of the high alloy roller sleeve is sprayed with water and blown with air. The surface of the high alloy roller sleeve is sprayed with water to 550°C, and then the surface of the high alloy roller sleeve is blown with air to prevent temperature reversal. The blowing is stopped after the temperature drops to 540°C, and finally the high alloy roller sleeve continues to slowly cool to 400-450°C; Step S5, performing tempering twice at 500-550° C. for 10-15 hours.

2. The inner wall stress control and heat treatment method of the high-speed steel outer casing of the coiler combination roller according to claim 1 is characterized in that: In the step S1, the casting thickness ratio of the outer layer and the inner wall of the high alloy roller sleeve is less than 1.

0.

3. The inner wall stress control and heat treatment method of the high-speed steel outer shell of the coiler combination roller according to claim 1 is characterized by: In step S4, the cooling rate of spraying water on the surface of the high alloy roller sleeve reaches above 10°C / min.

4. The inner wall stress control and heat treatment method of the high-speed steel outer shell of the coiler combination roller according to claim 1 is characterized in that: In the step S5, when the outer layer hardness of the high alloy roller sleeve is required to be 70-80HS, the tempering temperature is 530-550°C; when the outer layer hardness of the high alloy roller sleeve is required to be 80-90HS, the tempering temperature is 500-530°C.

5. The inner wall stress control and heat treatment method of the high-speed steel outer shell of the coiler combination roller according to claim 1 is characterized in that: In the step S5, when the wall thickness of the high alloy roller sleeve is ≤100 mm, the tempering time is 10-12 hours; when the wall thickness of the high alloy roller sleeve is in the range of 100-180 mm, the tempering time is 12-15 hours.