A preliminary heat treatment method for reducing heat treatment deformation of Cr12MoV steel cold working die

Abstract

The present invention provides a preliminary heat treatment method for reducing the heat treatment deformation of a Cr12MoV steel cold working die, which is applicable to various cold working dies made of Cr12MoV steel, and the method includes the process of preliminary heat treatment, vacuum quenching, primary tempering, secondary tempering and the like of the Cr12MoV die. The preliminary heat treatment method for reducing the heat treatment deformation of a Cr12MoV steel cold working die provided by the present invention can greatly reduce the heat treatment deformation of the Cr12MoV steel cold working die by treating the Cr12MoV steel cold working die with a special preliminary heat treatment process method, and is applicable to precise and complex Cr12MoV steel cold working dies, and is also applicable to ordinary dies and other workpieces made of Cr12MoV steel.

Description

Technical Field

[0001] The invention relates to the technical field of heat treatment of cold working dies, and in particular to a preparatory heat treatment method for reducing heat treatment deformation of a Cr12MoV steel cold working die. Background Art

[0002] At present, for the preliminary heat treatment of Cr12MoV steel cold working dies, isothermal spheroidizing annealing process is generally used. Some people use high temperature tempering instead of isothermal spheroidizing annealing process, but they are all considered from the perspective of improving mechanical properties, and the process is quite complicated, with a long cycle and high cost. So far, there has been no research report on improving the preliminary heat treatment process from the perspective of deformation. Although the deformation of cold working die steel Cr12MoV is not large, for some molds with complex structures and high manufacturing precision requirements, they are often scrapped due to deformation, making the heat treatment deformation of Crl2MoV steel cold working dies a technical problem, especially with the advancement of science and technology, the requirements for complex and precision molds are increased, and the problem becomes more prominent. Summary of the invention

[0003] The purpose of the present invention is to provide a preliminary heat treatment method for reducing the heat treatment deformation of a Cr12MoV steel cold working die, so as to improve the anti-deformation performance of the Cr12MoV steel cold working die.

[0004] In order to solve the above technical problems, the present invention provides a preliminary heat treatment method for reducing the heat treatment deformation of a Cr12MoV steel cold working die, which is applicable to a cold working die made of Cr12MoV steel and comprises the following steps:

[0005] Preliminary heat treatment: load the furnace when the furnace temperature is ≤500℃, stay at 500℃±10℃ for 1-2 hours, heat up to 810℃±5℃ according to the power and stay for 1-2 hours, continue to heat to 870℃±5℃ and keep warm for 1-2 hours, cool the furnace to 710℃±5℃ and stay for 30 minutes; heat to 850℃±5℃, and the holding time is calculated as "effective thickness / 50-effective thickness / 40mm" hours, and after the holding is completed, cool the furnace to 710℃±5℃ and stay for 30 minutes; heat to 830℃±5℃ and keep warm for 1-2 hours, cool the furnace to 710℃±5℃ and stay for 30 minutes; heat to 750℃±5℃ and keep warm for 1-3 hours, cool the furnace to 710℃±5℃ and stay for 30 minutes; heat to 750℃±5℃ and keep warm for 1-3 hours, cool down to 400℃ at a rate of ≤30℃ per hour, and then take out of the furnace and air cool.

[0006] Vacuum quenching: heat up from cold furnace, stay at 580℃±10℃ for 1-2 hours, stay at 810℃±5℃ for 1-2 hours, keep quenching temperature at 1040℃±5℃ for 1-2 hours, quench at 0.6-0.8MPa gas pressure, and take out of the furnace at ≤50℃.

[0007] Primary tempering: heating according to power, tempering temperature 510℃±5℃, keep warm for 4-5 hours, then take out of the furnace

[0008] Cool with air.

[0009] Secondary tempering: heating according to power, tempering temperature 500℃±5℃, keep warm for 4-5 hours, then take out of the furnace

[0010] Cool with air.

[0011] Furthermore, in the preparatory heat treatment, the upper and lower limits of the heating temperature for the first three times are reduced by 20° C. successively; the upper and lower limits of the heating temperature for the last two times are exactly the same; and the intermediate temperature is lowered to 710° C. and stayed for 30 minutes.

[0012] Furthermore, the chemical composition of the Cr12MoV steel meets the requirements of GB / T 1299-2000 standard.

[0013] The present invention provides a preliminary heat treatment method for reducing heat treatment deformation of a Cr12MoV steel cold working die, which is applicable to various cold working dies made of Cr12MoV steel, and is also applicable to other workpieces made of Cr12MoV steel. The present invention provides a preliminary heat treatment method for reducing heat treatment deformation of a Cr12MoV steel cold working die, which can significantly reduce the heat treatment deformation of the Cr12MoV steel cold working die by using the preliminary heat treatment process of the present invention to treat the Cr12MoV steel cold working die. DETAILED DESCRIPTION

[0014] In order to reduce the stress of controlling the Cr12MoV steel cold working die and various factors affecting deformation, and achieve the purpose of reducing heat treatment deformation, the present invention provides a preliminary heat treatment method for reducing heat treatment deformation of the Cr12MoV steel cold working die, which is suitable for various cold working dies made of Cr12MoV steel, and the chemical composition of the Cr12MoV steel meets the requirements of GB / T 1299-2000 standard. The method comprises the following steps:

[0015] (1) Preliminary heat treatment: load the furnace when the furnace temperature is ≤500℃, keep it at 500℃±10℃ for 1-2 hours, heat it to 810℃±5℃ according to the power and keep it for 1-2 hours, continue to heat it to 870℃±5℃ and keep it for 1-2 hours, cool it to 710℃±5℃ and keep it for 30 minutes; heat it to 850℃±5℃, the holding time is calculated as "effective thickness / 50-effective thickness / 40mm" hours, after the holding is completed, cool it to 710℃±5℃ and keep it for 30 minutes; heat it to 830℃±5℃ and keep it for 1-2 hours, cool it to 710℃±5℃ and keep it for 30 minutes; heat it to 750℃±5℃ and keep it for 1-3 hours, cool it to 710℃±5℃ and keep it for 30 minutes; heat it to 750℃±5℃ and keep it for 1-3 hours, cool it to 400℃ at a rate of ≤30℃ per hour and air cool it out of the furnace.

[0016] (2) Vacuum quenching: Heat up from a cold furnace, stay at 580℃±10℃ for 1-2 hours, stay at 810℃±5℃ for 1-2 hours, keep the quenching temperature at 1040℃±5℃ for 1-2 hours, quench at a gas pressure of 0.6-0.8MPa, and take out of the furnace at ≤50℃.

[0017] (3) Tempering: Heat up according to power, tempering temperature 510℃±5℃, keep warm for 4-5 hours,

[0018] Take out of the oven and blow air to cool.

[0019] (4) Secondary tempering: heating according to power, tempering temperature 500℃±5℃, keep warm for 4-5 hours, and cool by blowing. The following is a detailed description of a preliminary heat treatment method for reducing heat treatment deformation of Cr12MoV steel cold working die provided by the present invention in conjunction with the embodiments.

[0020] Example 1

[0021] Cr12MoV steel cold working die material, its chemical composition: C: 1.56wt.%; Si: 0.30 wt.%; Mn: 0.35wt.%; Cr: 11.50 wt.%; Mo: 0.45wt.%; V: 0.20wt.%; S: 0.01 wt.%; P: 0.02 wt.%. Heat treatment thereof includes the following steps:

[0022] (1) Preliminary heat treatment: Load the furnace at room temperature, heat up according to the power, stay at 500℃ for 1 hour, stay at 810℃ for 1.5 hours, heat up to 870℃ and keep it for 1 hour, cool the furnace to 710℃ and stay for 30 minutes; heat up according to the power, keep it at 850℃ for 1 hour, cool the furnace to 710℃ and stay for 30 minutes after the heat preservation; heat up to 830℃ and keep it for 1 hour, cool the furnace to 710℃ and stay for 30 minutes; heat up to 750℃ and keep it for 1 hour, cool the furnace to 710℃ and stay for 30 minutes; heat up to 750℃ and keep it for 1 hour, cool the furnace to 710℃ and stay for 30 minutes; heat up to 750℃ and keep it for 1 hour, cool the furnace to 400℃ at a rate of 30℃ per hour and air cool out of the furnace.

[0023] (2) Vacuum quenching: Heat up from a cold furnace, stay at 580°C for 1 hour, stay at 810°C for 1.5 hours, keep the quenching temperature at 1040°C for 1.5 hours, quench at a gas pressure of 0.6 MPa, and take out of the furnace at 50°C.

[0024] (3) Primary tempering: Heat up according to power, tempering temperature 510℃, keep warm for 4 hours, and cool by blowing after taking out of the furnace.

[0025] (4) Secondary tempering: Heat up according to power, tempering temperature 500℃, keep warm for 4 hours, and cool by blowing after taking out of the furnace.

[0026] Comparative Example 1

[0027] The difference from Example 1 is that step (1) adopts a conventional isothermal spheroidizing annealing process, that is, keeping at 860°C for 3 hours, cooling to 740°C for 4 hours, cooling to 500°C and air cooling.

[0028] The size is roughly measured with a caliper and accurately measured with a tool microscope. After testing, the deformation data of the cylindrical deformation specimen of the cold working die of Cr12MoV material in Example 1 after heat treatment using the "preparatory heat treatment process of the present invention" and the deformation data of the cylindrical deformation specimen of Comparative Example 1 are shown in Table 1. From the comparison in Table 1, it can be seen that the deformation of Example 1 is greatly reduced than that of Comparative Example 1. The deformation data of the annular deformation specimens of Example 1 and Comparative Example 1 are shown in Table 2. The deformation of Example 1 is also greatly reduced than that of Comparative Example 1. The hardness of Example 1 and Comparative Example 1 is HRC56.5.

[0029] Table 1 Deformation data of notch size of cylindrical deformation specimens of Example 1 and Comparative Example 1

[0030] serial number Three dimensions before quenching and tempering Three dimensions after quenching and tempering Total deformation Example 1 12.02、12.02、12.02 12.01、12.02、12.01 -0.0067 Comparative Example 1 12.02、12.03、12.02 11.99、12.00、12.00 -0.0267

[0031] Table 2 Deformation data of the opening size of the circular ring deformation specimens of Example 1 and Comparative Example 1

[0032] serial number Three dimensions before quenching and tempering Three dimensions after quenching and tempering Total deformation Example 1 6.02,6.03,6.03 6.04,6.04,6.03 +0.010 Comparative Example 1 6.01,6.01,6.02 6.05,6.04,6.03 +0.027

[0033] Example 2

[0034] Cr12MoV steel cold working die material, its chemical composition: C: 1.56wt.%; Si: 0.30 wt.%; Mn: 0.35wt.%; Cr: 11.50 wt.%; Mo: 0.45wt.%; V: 0.20wt.%; S: 0.01 wt.%; P: 0.02 wt.%. Heat treatment thereof includes the following steps:

[0035] (1) Preliminary heat treatment: Load the furnace at room temperature, heat up according to the power, stay at 500℃ for 1 hour, stay at 810℃ for 1 hour, heat up to 870℃ and keep warm for 1 hour, cool the furnace to 710℃ and stay for 30 minutes; heat up according to the power, keep warm at 850℃ for 1 hour, cool the furnace to 710℃ and stay for 30 minutes; heat to 830℃ and keep warm for 1 hour, cool the furnace to 710℃ and stay for 30 minutes; heat to 750℃ and keep warm for 1 hour, cool the furnace to 710℃ and stay for 30 minutes; heat to 750℃ and keep warm for 1 hour, cool the furnace to 710℃ and stay for 30 minutes; heat to 750℃ and keep warm for 1 hour, cool the furnace to 400℃ at a rate of 30℃ per hour and air cool out of the furnace.

[0036] (2) Vacuum quenching: Heat up from a cold furnace, stay at 580°C for 1 hour, stay at 810°C for 1 hour, keep the quenching temperature at 1040°C for 1.5 hours, quench at a gas pressure of 0.8 MPa, and take out of the furnace at 50°C.

[0037] (3) Primary tempering: Heat up according to power, tempering temperature 510℃, keep warm for 4 hours, and cool by blowing after taking out of the furnace.

[0038] (4) Secondary tempering: Heat up according to power, tempering temperature 500℃, keep warm for 4 hours, and cool by blowing after taking out of the furnace.

[0039] Comparative Example 2: The difference from Example 2 is that: Step (1) adopts a conventional isothermal spheroidizing annealing process, that is, keeping at 860°C for 3 hours, cooling to 740°C for 4 hours, cooling to 500°C and air cooling.

[0040] After testing, the deformation data of the cylindrical deformation specimen of the cold working die of Cr12MoV in Example 2 after heat treatment by the "preparatory heat treatment process of the present invention" are shown in Table 3, and the deformation data of Comparative Example 2 are shown in Table 3. From the comparison in Table 3, it can be seen that the deformation of Example 2 is greatly reduced than that of Comparative Example 2. The deformation data of the circular ring deformation specimens of Example 2 and Comparative Example 2 are shown in Table 4. The deformation of Example 2 is also greatly reduced than that of Comparative Example 2. The hardness of Example 2 and Comparative Example 2 is HRC56.

[0041] Table 3 Deformation data of notch size of cylindrical deformation specimens in Example 2 and Comparative Example 2

[0042] serial number Three dimensions before quenching and tempering Three dimensions after quenching and tempering Total deformation Example 2 12.01、12.02、12.02 12.01、12.00、12.01 -0.0100 Comparative Example 2 12.02、12.01、12.02 11.99、11.99、11.98 -0.0300

[0043] Table 4 Deformation data of the opening size of the circular ring deformation specimens of Example 2 and Comparative Example 2

[0044] serial number Three dimensions before quenching and tempering Three dimensions after quenching and tempering Total deformation Example 2 6.02,6.03,6.03 6.04,6.04,6.04 +0.013 Comparative Example 2 6.01,6.02,6.02 6.05,6.04,6.04 +0.027

[0045] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A preliminary heat treatment method for reducing heat treatment deformation of Cr12MoV steel cold working dies, which is suitable for various cold working dies made of Cr12MoV steel, and is characterized in that: The following steps are involved: Preliminary heat treatment: load the furnace when the furnace temperature is ≤500℃, stay at 500℃±10℃ for 1-2 hours, heat up to 810℃±5℃ according to the power and stay for 1-2 hours, continue to heat to 870℃±5℃ and keep warm for 1-2 hours, cool the furnace to 710℃±5℃ and stay for 30 minutes; heat to 850℃±5℃, the holding time is calculated according to "effective thickness mm / 50~effective thickness mm / 40" hours, after the holding is finished, cool the furnace to 710℃±5℃ and stay for 30 minutes; heat to 830℃±5℃ and keep warm for 1-2 hours, cool the furnace to 710℃±5℃ and stay for 30 minutes; heat to 750℃±5℃ and keep warm for 1-3 hours, cool the furnace to 710℃±5℃ and stay for 30 minutes; heat to 750℃±5℃ and keep warm for 1-3 hours, cool to 400℃ at a rate of ≤30℃ per hour, and then air cool out of the furnace; Vacuum quenching: cold furnace heating, stay at 580℃±10℃ for 1-2 hours, stay at 810℃±5℃ for 1-2 hours, quenching temperature 1040℃±5℃ for 1-2 hours, quench at 0.6-0.8MPa gas pressure, ≤50℃ out of the furnace; Primary tempering: heating according to power, tempering temperature 510℃±5℃, keep warm for 4-5 hours, take out of the furnace and cool by blowing; Secondary tempering: increase the temperature according to the power, the tempering temperature is 500℃±5℃, keep warm for 4-5 hours, and cool it by blowing air after it comes out of the furnace.

2. A preliminary heat treatment method for reducing heat treatment deformation of Cr12MoV steel cold working die according to claim 1, characterized in that: The chemical composition of the Cr12MoV steel meets the requirements of GB / T 1299-2000 standard.