Heat treatment method for forged steel cold rolling work rolls

Abstract

The present invention discloses a heat treatment method for a forged steel cold rolling work roll, which has the following steps: S1: Overall preheating; S2: Machine tool induction annealing; S3: Final heat treatment. The machine tool induction annealing in step S2 specifically includes: placing the forged steel cold rolling work roll that has been overall preheated in step S1 on a power frequency induction quenching machine tool, first inductively heating it to 600 - 850 °C and holding for 1 - 2 h; then inductively heating it to 900 - 1000 °C and holding for 1 - 2 h; finally placing it in an oven at 200 - 400 °C and holding for 24 - 60 h. The heat treatment method of the present invention can enable unqualified forged steel cold rolling work rolls with the surface hardness and hardened layer depth of the roll body not meeting the use requirements to obtain a higher surface hardness of the roll body and a deeper hardened layer depth through overall preheating + machine tool induction annealing + re-surface quenching, meeting the use requirements, thereby greatly reducing the production cost of the enterprise and improving the production efficiency of the enterprise.

Description

Technical Field

[0001] The present invention belongs to the technical field of forged steel cold rolling work rolls, and particularly relates to a heat treatment method for forged steel cold rolling work rolls. Background Art

[0002] At present, with the development of modernization, high speed and large scale of rolling mills, the requirements of enterprises for the service performance of forged steel cold rolling work rolls are becoming increasingly strict. In recent years, in order to meet the service performance requirements such as service hardness, working layer depth, surface flaw detection, etc., the composition and process of forged steel cold rolling work rolls have been continuously optimized and changed.

[0003] In order to meet a certain surface hardness of the roll body (i.e., the above-mentioned service hardness) and the hardened layer depth (i.e., the above-mentioned working layer depth), forged steel cold rolling work rolls usually need to be subjected to surface induction hardening. Conventional hardening methods include two categories: dual-frequency induction hardening and power-frequency induction hardening.

[0004] However, in the actual production process, these two conventional hardening methods often result in the situation that the surface hardness of the roll body and the hardened layer depth do not meet the service requirements, leading to the disqualification of the produced forged steel cold rolling work rolls. For these disqualified forged steel cold rolling work rolls, they usually can only be scrapped, which greatly increases the production cost of enterprises and reduces the production efficiency of enterprises. Summary of the Invention

[0005] The purpose of the present invention is to solve the above problems and provide a heat treatment method for forged steel cold rolling work rolls that can make the surface hardness of the roll body and the hardened layer depth of disqualified forged steel cold rolling work rolls meet the service requirements.

[0006] The technical solution for realizing the purpose of the present invention is: a heat treatment method for forged steel cold rolling work rolls, which has the following steps:

[0007] S1: Overall preheating;

[0008] S2: Machine tool induction annealing;

[0009] S3: Final heat treatment.

[0010] The overall preheating temperature of the above step S1 is 200 - 400 °C, and the time is 24 - 60 h.

[0011] Before the overall preheating of the above step S1, it is necessary to first perform dimensional detection and recording on the main form and position tolerance files of the forged steel cold rolling work roll, and at the same time optimize the chamfer structure.

[0012] The machine tool induction annealing in step S2 specifically includes: placing the forged steel cold rolling work roll preheated as a whole in step S1 on an industrial frequency induction quenching machine tool, first induction heating to 600 - 850 °C and holding for 1 - 2 h; then induction heating to 900 - 1000 °C and holding for 1 - 2 h; finally placing it in an oven at 200 - 400 °C and holding for 24 - 60 h.

[0013] Before and after the machine tool induction annealing in step S2, attention needs to be paid to the protection of the roll neck and bearing seats. Among them: anti-oxidation layers need to be coated on each gear of the roll neck; for the bearing seats, in addition to coating anti-oxidation layers, they also need to be wrapped with asbestos paper and bandaged with lead wire to avoid being bruised or excessive oxidation during low-temperature tempering.

[0014] The final heat treatment in step S3 specifically includes: overall preheating at 200 - 400 °C for 12 - 48 h, surface quenching treatment at 880 - 1000 °C; tempering treatment at 100 - 300 °C for 50 - 150 h.

[0015] Before the final heat treatment in step S3, ultrasonic testing (UT) and surface ultrasonic testing (SUT) need to be carried out on the roll body of the forged steel cold rolling work roll, and it can only be carried out after there are no defects.

[0016] The positive effects of the present invention: The heat treatment method of the present invention can enable unqualified forged steel cold rolling work rolls with insufficient surface hardness and hardened layer depth of the roll body to obtain a higher surface hardness of the roll body and a deeper hardened layer depth through overall preheating + machine tool induction annealing + re-surface quenching, meeting the usage requirements, thereby greatly reducing the production cost of the enterprise and improving the production efficiency of the enterprise. Specific embodiments

[0017] (Embodiment 1)

[0018] The forged steel cold rolling work roll in this embodiment is of conventional Cr5 material, the surface hardness of the roll body is 89 - 90 HSD, and the hardened layer depth ≤ 20 mm.

[0019] The usage performance requirements are: the surface hardness of the roll body is 95 - 98 HSD, and the hardened layer depth ≥ 30 mm.

[0020] The heat treatment method of the forged steel cold rolling work roll in this embodiment has the following steps:

[0021] S1: Overall preheating, the temperature is 300 ± 10 °C, and the time is 40 h.

[0022] Before overall preheating, it is necessary to first measure and record the main geometric tolerance gears of the forged steel cold rolling work roll, and at the same time optimize the chamfer structure.

[0023] S2: Machine tool induction annealing, specifically including:

[0024] The forged steel cold-rolled working roll preheated as a whole in step S1 is placed on an industrial frequency induction quenching machine, first induction heated to 725±10°C and kept warm for 1.5 hours; then induction heated to 950±10°C and kept warm for 1.5 hours; finally placed in an oven at 300±10°C and kept warm for 40 hours.

[0025] Before and after induction annealing of machine tools, attention should be paid to the protection of roller neck stops and bearing stops. Among them: each roller neck stop needs to be coated with an anti-oxidation layer; in addition to being coated with an anti-oxidation layer, the bearing stop also needs to be wrapped with asbestos paper and lead wire to avoid collision or excessive oxidation during low-temperature tempering.

[0026] The surface hardness of the roller body after induction annealing of the machine tool is 47~48HSD.

[0027] S3: Final heat treatment, including:

[0028] Preheat the whole machine to 300±10℃ for 30h.

[0029] Surface quenching treatment, temperature is 940±5℃.

[0030] Tempering treatment, temperature is 200±10℃, time is 90h.

[0031] Before the final heat treatment, the forged steel cold rolling work roll body needs to be inspected by UT and SUT, and can only be carried out after no defects are found.

[0032] The surface hardness of the roller body after the final heat treatment is 96-97HSD, and the depth of the hardened layer is 33-34mm.

[0033] (Example 2 to Example 3)

[0034] The material and performance of the forged steel cold-rolled working rolls in each embodiment are the same as those in Embodiment 1, and the differences are shown in Table 1.

[0035] Table 1

[0036] Example 1 Example 2 Example 3 S1 Overall preheating 300±10℃，40h 250±10℃，50h 350±10℃，30h S2 Machine tool induction annealing 725 ± 10°C, 1.5 h; 950 ± 10°C, 1.5 h; 300 ± 10°C, 40 h 650 ± 10°C, 2 h; 920 ± 10°C, 2 h; 250 ± 10°C, 50 h 800 ± 10°C, 1 h; 980 ± 10°C, 1 h; 350 ± 10°C, 30 h Roll body surface hardness after machine tool induction annealing 47 - 48 HSD 46 - 47 HSD 48 - 49 HSD S3 Final heat treatment Overall preheating at 300 ± 10°C for 30 h; surface hardening treatment at 940 ± 5°C; tempering treatment at 200 ± 10°C for 90 h Overall preheating at 250 ± 10°C for 40 h; surface hardening treatment at 920 ± 5°C; tempering treatment at 150 ± 10°C for 120 h Overall preheating at 350 ± 10°C for 20 h; surface hardening treatment at 960 ± 5°C; tempering treatment at 250 ± 10°C for 60 h Roll body surface hardness after final heat treatment 96 - 97 HSD 95 - 96 HSD 97 - 98 HSD Hardened layer depth after final heat treatment 33 - 34 mm 31 - 32 mm 35 - 36 mm

Claims

1. A heat treatment method for a forged cold-rolled work roll to make the surface hardness and hardened layer depth of the roll body of the unqualified forged cold-rolled work roll meet the usage requirements, characterized in that it has the following steps: S1: Overall preheating; S2: Machine tool induction annealing; specifically including: placing the forged cold-rolled work roll that has been overall preheated in step S1 on an industrial frequency induction quenching machine tool, first induction heating to 600 - 850 °C and holding for 1 - 2 h; then induction heating to 900 - 1000 °C and holding for 1 - 2 h; finally placing it in an oven at 200 - 400 °C and holding for 24 - 60 h; S3: Final heat treatment; specifically including: overall preheating at 200 - 400 °C for 12 - 48 h, surface quenching treatment at 880 - 1000 °C; tempering treatment at 100 - 300 °C for 50 - 150 h.

2. The heat treatment method for a forged cold-rolled work roll to make the surface hardness and hardened layer depth of the roll body of the unqualified forged cold-rolled work roll meet the usage requirements according to claim 1, characterized in that: the overall preheating temperature in step S1 above is 200 - 400 °C and the time is 24 - 60 h.