CN106367566A - Method for testing performance of Cr12 die steel for stamping die - Google Patents

Abstract

The invention discloses a method for testing the performance of Cr12 die steel for stamping dies, comprising the steps of: S1, providing a first sample, and performing a first heat treatment process on the first sample, wherein the material of the first sample is Cr12 die steel; S2 . A second sample is provided, and a second heat treatment process is performed on the second sample. The material of the second sample is Cr12 die steel; S3. The performance of the first sample and the second sample is compared. Stamping die of the present invention uses Cr12 die steel performance test method, by adopting different heat treatment processes to two kinds of die steel samples to process, and compare the structure and performance of two kinds of die steel samples, thereby according to the comparison result, there is It helps to make an intuitive judgment on whether the improved heat treatment process for the stamping die can improve the service life of the stamping die.

Description

Performance test method of Cr12 die steel for stamping die

technical field

The invention belongs to the technical field of stamping dies, in particular, the invention relates to a method for testing the properties of Cr12 die steel used in stamping dies.

Background technique

Stamping dies belong to cold working die steel, which require high hardness, strength and wear resistance, as well as good plasticity and toughness during use. A company uses stamping punches to punch stainless steel circular parts. The mold material is Cr12 die steel, which is treated by ordinary quenching and low temperature tempering. The mold is prone to chipping and chipping defects during use. The failure of the stamping punch will not only affect the shape, size and precision of the stamping parts, but also waste production time due to frequent mold replacement, reduce productivity, and affect the company's economic benefits. The main reason for the stamping die failure is high brittleness and low toughness. For this reason, it is necessary to change the original heat treatment process of the stamping die to improve its toughness, reduce brittleness, and increase the service life of the stamping die. As for whether the improved heat treatment process can increase the service life of the stamping die, an effective method needs to be used to verify, which is lacking in the prior art.

Contents of the invention

The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the present invention provides a method for testing the performance of Cr12 die steel for stamping dies, with the purpose of verifying whether the improved heat treatment process of the stamping dies can improve the service life of the stamping dies.

In order to achieve the above object, the technical scheme that the present invention takes is: stamping die is used Cr12 die steel performance test method, comprises steps:

S1. Provide the first sample, and carry out the first heat treatment process on the first sample. The material of the first sample is Cr12 die steel;

S2, provide the second sample, carry out the second heat treatment process to the second sample, the material of the second sample is Cr12 mold steel;

S3. Comparing the performance of the first sample and the second sample.

The first heat treatment process includes steps:

S11, spheroidizing annealing;

S12, quenching;

S13, low temperature tempering.

In the step S12, the heating temperature during quenching is 970-990° C., and the holding time is 14-16 minutes.

In the step S12, the first sample is cooled by oil cooling.

In the step S13, the tempering temperature is 210-230° C., and the holding time is 14-16 minutes.

In the step S13, the first sample is cooled by air cooling.

The second heat treatment process includes steps:

S21, spheroidizing annealing;

S22, sample austenitization;

S23, pre-quenching;

S24, isothermal quenching;

S25, the first low temperature tempering;

S26. Tempering at low temperature for the second time.

In the step S22, the second sample is heated to 1020-1040° C. for austenitization, and the holding time for austenitization is 14-16 minutes.

In the step S23, the second sample is placed in quenching oil for pre-quenching, and the temperature of the quenching oil is 170-190°C.

In the step S24, the second sample is placed in a salt bath with an isothermal temperature of 270-290° C. for 28-32 minutes, and finally the second sample is taken out for air cooling.

In the step S25, the tempering temperature is 210-230° C., and the holding time is 14-16 minutes.

In the step S26, the tempering temperature is 210-230° C., and the holding time is 14-16 minutes.

Stamping die of the present invention uses Cr12 die steel performance test method, by adopting different heat treatment processes to two kinds of die steel samples to process, and compare the structure and performance of two kinds of die steel samples, thereby according to the comparison result, there is It helps to make an intuitive judgment on whether the improved heat treatment process for the stamping die can improve the service life of the stamping die.

Description of drawings

This manual includes the following drawings, the contents shown are:

Fig. 1 is the metallographic structure of the first sample after ordinary quenching and low temperature tempering;

Fig. 2 is the metallographic structure of Cr12 steel after spheroidizing annealing;

Fig. 3 is the metallographic structure of the second sample after austempering;

Fig. 4 is the metallographic structure of the second sample after austempering+two low-temperature tempering treatments;

detailed description

The specific embodiment of the present invention will be described in further detail by describing the embodiments below with reference to the accompanying drawings, the purpose is to help those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solutions of the present invention, and contribute to its implementation.

The invention provides a method for testing the performance of Cr12 die steel for stamping dies, comprising the following steps:

S1. Provide a first sample, and perform a first heat treatment process on the first sample;

S2. Provide a second sample, and perform a second heat treatment process on the second sample;

S3. Comparing the performance of the first sample and the second sample.

Specifically, the materials of the first sample and the second sample are both Cr12 die steel, and the first sample and the second sample each include two steel blocks of different sizes and made of Cr12 die steel, one of which is One is a steel block with a length, width and height of 10mm×10mm×15mm, and the other is a steel block with a length, width and height of 10mm×10mm×55mm and a U-shaped notch.

When heat treating the first sample, the first heat treatment process includes the following steps:

S11, spheroidizing annealing;

S12, quenching;

S13, low temperature tempering.

In step S11, the heating temperature for spheroidizing and annealing the first sample is 850-870° C., the holding time is 14-16 minutes (min), and finally the first sample is cooled by furnace cooling.

In step S12, the heating temperature for quenching the first sample is 970-990° C., the holding time is 14-16 minutes (min), and finally the first sample is cooled by oil cooling.

In step S13, when tempering the first sample, the tempering temperature is 210-230° C., the holding time is 14-16 minutes (min), and finally the first sample is cooled by air cooling.

When heat treating the first sample, the first heat treatment process also includes the following steps:

S14, measuring the performance of the first sample.

After completing the low-temperature tempering treatment on the first sample, proceed to step S14. In operation S14, the first sample is first ground and polished, then corroded with 4% nitric acid alcohol, and then the metallographic structure of the first sample is measured with a 4XC-D metallographic microscope , Then use the HV-1000 microhardness tester to measure the hardness of the first sample, and finally use the JBDS-300Y impact testing machine to measure the impact toughness of the first sample.

The structure of the first sample after spheroidizing annealing is shown in Figure 1, which is granular carbide + flaky pearlite; the structure of the first sample after ordinary quenching and low-temperature tempering is shown in Figure 2, which is tempered Martensite + carbide + retained austenite. The first sample contains high carbon content and alloy element content, which belongs to ledeburite steel. After quenching, flake martensite and carbide Cr ₇ C ₃ are obtained. Because carbon and alloying elements reduce the martensite transformation start temperature and end temperature, some austenite does not transform at room temperature and becomes retained austenite. During the tempering process, the lamellar martensite decomposes into tempered martensite, and the retained austenite and carbide obtained by quenching remain unchanged and remain.

When heat treating the second sample, the second heat treatment process includes the following steps:

S21, spheroidizing annealing;

S22, sample austenitization;

S23, pre-quenching;

S24, isothermal quenching;

S25, the first low temperature tempering;

S26. Tempering at low temperature for the second time.

In step S21, when the second sample is subjected to spheroidizing annealing, the heating temperature is 850-870° C., the holding time is 14-16 minutes (min), and finally it is slowly cooled to 490-510° C. and then air-cooled. The main purpose of the spheroidizing annealing of the second sample is to obtain granular carbides for the second sample to prepare for the final heat treatment.

In step S22, the second sample after the spheroidizing annealing treatment is heated to 1020-1040° C. for austenitization, and the holding time for austenitization is 14-16 minutes (min).

In step S23, pre-quenching refers to the process of placing the austenitized second sample in quenching oil for cooling treatment. The temperature of the quenching oil is 170-190° C., and the cooling time is 1-2 seconds (s ), the purpose is to transform austenite into martensite.

In step S24, the pre-quenched second sample is quickly placed in a salt bath with an isothermal temperature of 270-290° C. for 28-32 minutes (min), and finally the second sample is taken out for air cooling. The composition of the salt bath is 55% KNO3+45% NaNO2. Pre-quenching will transform part of the austenite into lamellar martensite, and part of the austenite will be transformed into lower bainite during the isothermal process in the salt bath at 270-290 ° C, but due to incomplete transformation, there are still a small amount of austenite Tentenite has not been transformed and becomes retained austenite. The microstructure of the second sample after pre-quenching + austempering is shown in Figure 3.

In step S25, the first low-temperature tempering treatment is performed on the second sample, the tempering temperature is 210-230° C., the holding time is 14-16 minutes (min), and finally the second sample is cooled by air cooling.

In step S26, the second sample is subjected to a second low-temperature tempering treatment, the tempering temperature is 210-230° C., the holding time is 14-16 minutes (min), and finally the second sample is cooled by air cooling.

The purpose of the first low-temperature tempering of the second sample is to remove the stress generated in the quenching process, and the purpose of the second low-temperature tempering of the second sample is to remove the stress generated in the first low-temperature tempering process, and Decompose part of the retained austenite to stabilize the structure and size. The structure of the second sample after two low-temperature tempering treatments is lower bainite + tempered martensite + a small amount of retained austenite + carbide, as shown in Figure 4.

When performing heat treatment on the second sample, the second heat treatment process also includes the following steps:

S27. Measure the performance of the second sample.

After completing the second low-temperature tempering treatment on the second sample, proceed to step S27. In step S27, the metallographic structure, hardness and impact toughness of the second sample after austenitization + pre-quenching + austempering + secondary low-temperature tempering are measured.

In step S3, the metallographic structure, hardness and impact toughness of the second sample are compared with the metallographic structure, hardness and impact toughness of the first sample subjected to spheroidizing annealing + ordinary quenching + low temperature tempering treatment before improvement, Compare the changes in their performance. The values of hardness and impact toughness are shown in Table 1. It can be seen that the hardness of the first sample and the second sample with different heat treatment processes have little change, but compared with the first sample, the impact toughness of the second sample Significantly improved.

Table 1 Hardness and impact toughness values of the first sample and the second sample after heat treatment

The second sample adopts sample austenitization + pre-quenching + austempering + two low-temperature tempering treatments to obtain flaky martensite and lower bainite. Flaky martensite has higher hardness, and lower bainite has higher impact toughness and lower brittle transition temperature. Through two low-temperature tempering, the structural stress caused by quenching can be eliminated, and part of the austenite can be transformed to stabilize the structure and ensure the dimensional stability of the stamping die.

For stamping dies made of Cr12 die steel in the prior art, if the stamping dies are successively subjected to spheroidizing annealing, ordinary quenching and low-temperature tempering (i.e. the first heat treatment process above), the organization after quenching is flaky martensite, Carbide and retained austenite, in which the lamellar martensite contains supersaturated carbon, will produce a significant solid solution strengthening effect, resulting in an increase in strength and hardness. At the same time, the substructure of the lamellar martensite is twin, which also hinders the movement of faults and improves the strength and hardness. In addition, the carbides obtained by quenching are hard and brittle, distributed on the matrix of lamellar martensite, and the strength and hardness of the structure are further improved by the second phase strengthening. Therefore, after quenching, the Cr12 steel stamping die has high strength and hardness, but high brittleness and low toughness. After low-temperature tempering, the retained austenite and carbides remain unchanged and remain. The flake martensite decomposes into tempered martensite, which basically retains the high hardness and strength after quenching. It is this hard and brittle structure that causes cracking and chipping defects in the production process of Cr12 steel stamping dies.

If the heat treatment process is improved, the stamping die is sequentially subjected to spheroidizing annealing, austenitization, pre-quenching, austempering and two low-temperature tempering treatments (that is, the second heat treatment process above), and the lower bainite and tempering processes can be obtained. Fire martensite, carbide and a small amount of retained austenite. Lower bainite not only has high strength and hardness, but also has good toughness. Through two low-temperature tempering, the stress can be eliminated, and part of the austenite can be transformed to stabilize the structure and ensure the dimensional stability of the stamping die. By improving the heat treatment process, the impact toughness of the stamping die is improved, the stress is reduced, cracking and chipping can be avoided, and the service life of the stamping die is improved.

In the test method of the present invention, the first sample and the second sample are treated separately by using different heat treatment processes, the heat treatment process used by the first sample is the same as the heat treatment process before the stamping die is improved, and the heat treatment process used by the second sample is The heat treatment process is the same as the improved heat treatment process of the stamping die. On the one hand, the metallographic structure, hardness and impact toughness of Cr12 die steel are effectively measured. On the other hand, the metallographic structure and properties of the two samples are compared. , so that according to the comparison results, it is helpful to make an intuitive judgment on whether the improved heat treatment process for the stamping die can improve the service life of the stamping die, and provide an effective means of verification.

Embodiment one

The present embodiment provides a kind of Cr12 die steel performance test method for stamping die, comprises the following steps:

S1. Provide a first sample, and perform a first heat treatment process on the first sample;

S2. Provide a second sample, and perform a second heat treatment process on the second sample;

S3. Comparing the performance of the first sample and the second sample.

When heat treating the first sample, the first heat treatment process includes the following steps:

S11, spheroidizing annealing;

S12, quenching;

S13, low temperature tempering;

S14, measuring the performance of the first sample.

In step S11, the heating temperature for spheroidizing and annealing the first sample is 860° C., the holding time is 15 minutes (min), and finally the first sample is cooled by furnace cooling.

In step S12, the heating temperature for quenching the first sample was 980° C., the holding time was 15 minutes (min), and finally the first sample was cooled by oil cooling.

In step S13, when the first sample is tempered, the tempering temperature is 220° C., the holding time is 15 minutes (min), and finally the first sample is cooled by air cooling.

When heat treating the second sample, the second heat treatment process includes the following steps:

S21, spheroidizing annealing;

S22, sample austenitization;

S23, pre-quenching;

S24, isothermal quenching;

S25, the first low temperature tempering;

S26, the second low temperature tempering;

S27. Measure the performance of the second sample.

In step S21, when the second sample is subjected to spheroidizing annealing, the heating temperature is 860° C., the holding time is 15 minutes (min), and finally it is slowly cooled to 400° C. and then air-cooled.

In step S22, the second sample after the spheroidizing annealing treatment was heated to 1030° C. for austenitization, and the holding time for austenitization was 15 minutes (min).

In step S23, pre-quenching refers to the process of placing the austenitized second sample in quenching oil for cooling treatment. The temperature of the quenching oil is 180° C., and the cooling time is 1 second (s).

In step S24, the pre-quenched second sample was quickly placed in a salt bath with an isothermal temperature of 280° C. for 30 minutes (min), and finally the second sample was taken out for air cooling.

In step S25, the first low-temperature tempering treatment was performed on the second sample, the tempering temperature was 220° C., the holding time was 15 minutes (min), and finally the second sample was cooled by air cooling.

In step S26, the second sample is subjected to a second low-temperature tempering treatment, the tempering temperature is 220° C., the holding time is 15 minutes (min), and finally the second sample is cooled by air cooling.

The present invention has been exemplarily described above with reference to the accompanying drawings. Apparently, the specific implementation of the present invention is not limited by the above methods. As long as various insubstantial improvements are made using the method concept and technical solution of the present invention; or without improvement, the above-mentioned concept and technical solution of the present invention are directly applied to other occasions, all within the protection scope of the present invention within.

Claims (10)

1. diel with cr12 mould steel performance test methods it is characterised in that include step:

S1, offer the first sample, carry out the first Technology for Heating Processing, the material of the first sample is cr12 mould steel to the first sample；

S2, offer the second sample, carry out the second Technology for Heating Processing, the material of the second sample is cr12 mould steel to the second sample；

S3, the performance to the first sample and the second sample contrast.

2. diel according to claim 1 with cr12 mould steel performance test methods it is characterised in that described first Technology for Heating Processing includes operation:

S11, spheroidizing；

S12, quenching；

S13, lonneal.

3. diel according to claim 2 with cr12 mould steel performance test methods it is characterised in that described operation In s12, during quenching, heating-up temperature is 970-990 DEG C, and temperature retention time is 14-16min.

4. diel according to claim 3 with cr12 mould steel performance test methods it is characterised in that described operation In s12, using oil cooling mode, the first sample is cooled down.

5. according to the arbitrary described diel of claim 2 to 4 with cr12 mould steel performance test methods it is characterised in that In described operation s13, temperature is 210-230 DEG C, and temperature retention time is 14-16min.

6. diel according to claim 5 with cr12 mould steel performance test methods it is characterised in that described operation In s13, using air cooling mode, the first sample is cooled down.

7. according to the arbitrary described diel of claim 1 to 6 with cr12 mould steel performance test methods it is characterised in that Described second Technology for Heating Processing includes operation:

S21, spheroidizing；

S22, sample austenitizing；

S23, prequenching；

S24, isothermal hardening；

S25, first time lonneal；

S26, second lonneal.

8. diel according to claim 7 with cr12 mould steel performance test methods it is characterised in that described operation In s22, the second sample is heated to 1020-1040 DEG C, carries out austenitizing, austenitizing holding time is 14-16min.

9. the diel according to claim 7 or 8 with cr12 mould steel performance test methods it is characterised in that described In operation s23, the second sample is placed in quenching oil and carries out prequenching, the temperature of quenching oil is 170-190 DEG C.

10. the diel according to claim 7 or 8 with cr12 mould steel performance test methods it is characterised in that described In operation s24, the second sample is placed in the salt bath that isothermal temperature is 270-290 DEG C, isothermal time 28-32min, finally takes out Second sample carries out air cooling.