CN116356120A - Heat treatment process for improving toughness of H13 steel for hot rolling shear blade - Google Patents

Abstract

The invention relates to a heat treatment process for improving the toughness of H13 steel for a hot rolling shear blade, and belongs to the technical field of heat treatment of die steel. The thickness of the H13 steel for the hot rolling shear blade is 35-70 mm, and the concrete process comprises the following steps: heating H13 steel to 1080-1100 ℃, preserving heat for 25-35 min, discharging and cooling; then heating to 780-820 ℃, preserving heat for 2-2.5 h, discharging from the furnace, and air cooling to room temperature; then the mixture is put into a vacuum heating furnace, heated to 1040 to 1060 ℃, kept at the temperature for 30 to 40 minutes, and discharged and cooled; and finally, preserving the heat for 2-2.5 h at 300-350 ℃, air-cooling to room temperature, and tempering for three times to finish the heat treatment process. The H13 steel produced by the heat treatment process is sampled at the center to prepare a V-shaped notch Charpy impact sample, and the impact energy is more than or equal to 9.0J and the hardness is 52-56 HRC.

Description

A Heat Treatment Process for Improving the Strength and Toughness of H13 Steel for Hot-rolled Shear Blade

technical field

The invention belongs to the technical field of die steel heat treatment, and in particular relates to a heat treatment process for improving the strength and toughness of H13 steel for hot-rolled shear blades.

Background technique

Shearing cutters are important mechanical spare parts in the steel rolling industry. The quality of hot-rolled shearing blades directly affects the quality of rolled products, yield and production efficiency. H13 steel has high thermal strength, high toughness, excellent thermal fatigue resistance and comprehensive mechanical properties, and is widely used in the cold and hot shear blade manufacturing industry. With the continuous improvement of rolling technology such as controlled rolling and controlled cooling, the requirements for the quality of cutting blades are getting higher and higher. During the use of H13 steel hot cutting blades, due to poor matching of strength and toughness, early failures such as chipping and stacking of cutting edges are often caused. Reduced blade life. Therefore, improving the strength and toughness of H13 steel by means of heat treatment is an important way to improve the service life of cutting edge products, and it is of great significance to improve the quality of rolled products and reduce production costs.

The conventional heat treatment process of H13 steel hot-rolled shears is annealing + quenching + secondary high-temperature tempering to obtain a tempered sorbite structure with a hardness range of 48-52HRC. At the same time, high-temperature tempering can easily cause martensitic lath and carbonization Coarsening of the material, often due to low strength during use, causing early failure such as piled edges. The invention provides a heat treatment process suitable for H13 steel for cutting blades: high quenching and high recovery + quenching + three times of low temperature tempering, through the cooperative design of cutting blade pretreatment and quenching and tempering process, tempered martensite structure is obtained, and the hardness range At 52-56HRC, the uniformity of grain and structure is improved, the strength and toughness are matched, and the product use requirements are met.

Contents of the invention

The invention provides a heat treatment process for improving the strength and toughness of H13 steel used for hot-rolled shear blades. The process can obtain carbides with dispersed distribution and tempered martensite fine H13 steel structure, and avoid coarsening of carbides and martensite laths. , significantly improving the uniformity and toughness of the material structure.

In order to realize the above-mentioned purpose of the invention, the technical scheme that the present invention takes is:

A heat treatment process for improving the strength and toughness of H13 steel for hot-rolled shear blades, the thickness of the H13 steel for hot-rolled shear blades is 35-70mm, and the heat treatment process includes high-temperature quenching, high-temperature tempering, vacuum quenching, and low-temperature tempering Steps, the specific process is as follows:

(1) High-temperature quenching: put the H13 steel into the heating furnace, heat it to 1080-1100 ° C with the furnace, keep it warm for 25-35 minutes, and cool it out of the furnace with air or oil;

(2) High-temperature tempering: put the H13 steel treated in step (1) into the heating furnace, heat it to 780-820°C with the furnace, keep it warm for 2-2.5 hours, and then take it out of the furnace and air-cool it to room temperature;

(3) Vacuum quenching: Roughly process the H13 steel treated in step (2), put it into a vacuum heating furnace, heat it with the furnace to 1040-1060 °C, keep it warm for 30-40 minutes, and cool it out of the furnace with air or oil; here Rough machining refers to machining such as milling and drilling of tools to meet the requirements of tool size and shape;

(4) Low-temperature tempering: put the H13 steel treated in step (3) into the heating furnace, heat it to 300-350°C with the furnace, keep it warm for 2-2.5 hours, and cool it to room temperature in air, that is, complete one tempering, and repeat this process The steps are operated twice, and tempering is carried out three times in total to complete the heat treatment process.

The high-temperature quenching step also includes heating the H13 steel to 800-850° C. with the furnace after loading it into the heating furnace, keeping it warm for 40-60 minutes, and then raising the temperature to 1080-1100° C. to keep it warm.

In the high-temperature quenching step, air-cooling or oil-cooling is carried out to ≤100°C.

In the step of vacuum quenching, air cooling or oil cooling is carried out to ≤100°C.

The H13 steel produced by the above heat treatment process is sampled at the core, and processed into a V-notch Charpy impact sample of 10mm×10mm×55mm. After testing, the impact energy is ≥9.0J and the hardness is 52-56HRC.

In the present invention, the H13 steel is kept at 1080-1100°C for 25-35 minutes. On the one hand, high-temperature diffusion is used to further uniform the composition and reduce the elimination of band segregation; Obtain a uniform and fine single cryptocrystalline martensite structure, avoiding the influence of different types of pearlite and differences in carbide morphology on subsequent heat treatment.

In the present invention, the H13 steel after high-temperature quenching and cooling is heated to 780-820°C, kept for 2-2.5 hours, and air-cooled to room temperature to obtain a tempered sorbite structure with a hardness lower than 235HBW. Tempering replaces annealing, which is convenient for machining; on the other hand, before vacuum quenching, increase high-temperature tempering to change the structure state, avoid direct heating of martensite into austenite, and avoid austenite caused by uneven forging or improper heat treatment. Coarse crystals and mixed crystals are hereditary and affect the properties of materials.

In the present invention, the pretreated H13 steel is roughly machined, put into a vacuum heating furnace, quenched at 1040-1060°C and tempered three times at 300-350°C to obtain tempered martensite, effectively avoiding martensite caused by high-temperature tempering. Tensitic lath and carbide coarsening, under the premise of ensuring high hardness, taking into account the toughness of the material, three tempering can basically eliminate the residual austenite, ensuring the stability of the cutting edge during use.

After the treatment of the present invention, samples are taken from the H13 steel core, and processed into V-notch Charpy impact samples of 10mm×10mm×55mm, the impact energy in the quenched and tempered state is ≥9.0J, the hardness is 52-56HRC, and the tempered martensite structure Small, with better strength and toughness matching.

Description of drawings

Fig. 1 is the metallographic structure diagram after the H13 steel pretreatment of embodiment 1;

Fig. 2 is the SEM figure after the H13 steel pretreatment of embodiment 1;

Fig. 3 is the metallographic structure diagram of the H13 steel finished product of embodiment 1;

Fig. 4 is the SEM image of the H13 steel product of Example 1.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1

The 50mm thick H13 steel plate is selected, and the specific heat treatment process is as follows:

(1) High-temperature quenching: put the H13 steel shear blade blank into the heating furnace, heat it to 830°C with the furnace, keep it for 50 minutes, continue to heat up to 1090°C, keep it for 30 minutes, and cool it out of the furnace by air or oil to ≤100°C;

(2) High-temperature tempering: put the H13 steel treated in step (1) into the heating furnace, heat it to 800°C with the furnace, keep it for 2 hours, and air-cool it to room temperature after taking it out of the furnace to complete the pretreatment process;

(3) Vacuum quenching: Roughly process the H13 steel treated in step (2), put it into a vacuum heating furnace, heat up to 1050 °C with the furnace, keep it for 40 minutes, and cool it out of the furnace to ≤100 °C with air or oil;

(4) Low-temperature tempering: put the H13 steel pretreated in step (3) into the heating furnace, heat it up to 320°C with the furnace, keep it warm for 2.5 hours, and cool it to room temperature in air to complete one tempering, and then repeat the operation of this step Twice, for a total of three temperings.

After pretreatment and three low-temperature tempering treatments, samples were taken from the center of the H13 steel plate. After mechanical grinding and polishing, 4% nitric acid alcohol was used to corrode, and the transverse structure was observed. The metallographic structure and SEM structure of H13 steel after pretreatment As shown in Figure 1 and Figure 2, it can be seen from the figures that the tempered sorbite structure is fine and uniform, and the carbide spheroidization effect is obvious, which can provide good tissue preparation for tool quenching and tempering. The metallographic structure and SEM structure of the finished H13 steel after three times of low-temperature tempering are shown in Figure 3 and Figure 4. It can be seen from the figure that the tempered martensite lath bundles are fine, and the morphological characteristics of cryptocrystalline martensite are still retained. Under the premise of ensuring high hardness, take into account the toughness of the material. The average heat treatment hardness is 54.2HRC, and the average V-port Charpy impact energy is 9.6J.

Example 2

The 45mm thick H13 steel plate is selected, and the specific heat treatment process is as follows:

(1) High-temperature quenching: put the H13 steel shear blade blank into the heating furnace, heat it to 820°C with the furnace, keep it for 45 minutes, continue to heat up to 1090°C, keep it for 30 minutes, and cool it out of the furnace by air or oil to ≤100°C;

(2) High-temperature tempering: put the H13 steel treated in step (1) into the heating furnace, heat it to 800°C with the furnace, keep it for 2.5 hours, and air-cool it to room temperature after taking it out of the furnace to complete the pretreatment process;

(3) Vacuum quenching: Roughly process the H13 steel treated in step (2), put it into a vacuum heating furnace, heat up to 1050°C with the furnace, keep it warm for 35 minutes, and cool it out of the furnace to ≤100°C with air or oil;

(4) Low-temperature tempering: Put the H13 steel treated in step (3) into the heating furnace, heat it up to 320°C with the furnace, keep it warm for 2 hours, and cool it to room temperature in air to complete one tempering, and repeat this step twice , a total of three tempering.

After pretreatment and three tempering treatments, samples were taken from the center of the H13 steel plate, and after mechanical grinding and polishing, 4% nitric acid alcohol was used to corrode, and the transverse structure was observed. The structure was uniform and fine, and the carbides were dispersed. The average heat treatment hardness is 54.6HRC, and the average V-port Charpy impact energy is 9.6J.

Example 3

The 40mm thick H13 steel plate is selected, and the specific heat treatment process is as follows:

(1) High-temperature quenching: put the H13 steel shear blade blank into the heating furnace, heat it to 810°C with the furnace, keep it for 45 minutes, continue to heat up to 1080°C, keep it for 25 minutes, and cool it out of the furnace by air or oil to ≤100°C;

(2) High-temperature tempering: put the H13 steel treated in step (1) into the heating furnace, heat it to 780°C with the furnace, keep it for 2.5 hours, and air-cool it to room temperature to complete the pretreatment process;

(3) Vacuum quenching: Roughly process the H13 steel treated in step (2), put it into a vacuum heating furnace, heat it up to 1040°C with the furnace, keep it for 30 minutes, and cool it out of the furnace to ≤100°C with air or oil;

(4) Low-temperature tempering: Put the H13 steel treated in step (3) into the heating furnace, heat it up to 310°C with the furnace, keep it warm for 2.5 hours, and cool it to room temperature in air to complete one tempering, and repeat this step for two more times. times, a total of three tempering.

After pretreatment and three tempering treatments, samples were taken from the center of the H13 steel plate, and after mechanical grinding and polishing, 4% nitric acid alcohol was used to corrode, and the transverse structure was observed. The structure was uniform and fine, and the carbides were dispersed. The average heat treatment hardness is 55.2HRC, and the average V-port Charpy impact energy is 9.3J.

Example 4

The 35mm thick H13 steel plate is selected, and the specific heat treatment process is as follows:

(1) High-temperature quenching: put the H13 steel shear blade blank into the heating furnace, heat it to 800°C with the furnace, keep it for 40 minutes, continue to heat up to 1080°C, keep it for 25 minutes, and cool it out of the furnace by air or oil to ≤100°C;

(2) High-temperature tempering: put the H13 steel treated in step (1) into the heating furnace, heat it to 780°C with the furnace, keep it for 2 hours, and air-cool it to room temperature to complete the pretreatment process;

(3) Vacuum quenching: Roughly process the H13 steel treated in step (2), put it into a vacuum heating furnace, heat it up to 1040°C with the furnace, keep it for 30 minutes, and cool it out of the furnace to ≤100°C with air or oil;

(4) Low-temperature tempering: Put the H13 steel treated in step (3) into the heating furnace, heat it up to 300°C with the furnace, keep it warm for 2.5 hours, and cool it to room temperature in air to complete one tempering, and repeat this step for two more times. times, a total of three tempering.

After pretreatment and three tempering treatments, samples were taken from the center of the H13 steel plate, and after mechanical grinding and polishing, 4% nitric acid alcohol was used to corrode, and the transverse structure was observed. The structure was uniform and fine, and the carbides were dispersed. The average heat treatment hardness is 55.8HRC, and the average V-port Charpy impact energy is 9.2J.

Example 5

The 55mm thick H13 steel plate is selected, and the specific heat treatment process is as follows:

(1) High-temperature quenching: put the H13 steel shear blade blank into the heating furnace, heat it to 830°C with the furnace, keep it for 50 minutes, continue to heat up to 1095°C, keep it for 30 minutes, and cool it out of the furnace by air or oil to ≤100°C;

(2) High-temperature tempering: put the H13 steel treated in step (1) into the heating furnace, heat it to 800°C with the furnace, keep it for 2.5 hours, and air-cool it to room temperature after taking it out of the furnace to complete the pretreatment process;

(3) Vacuum quenching: Roughly process the H13 steel treated in step (2), put it into a vacuum heating furnace, heat up to 1050°C with the furnace, keep it warm for 35 minutes, and cool it out of the furnace to ≤100°C with air or oil;

(4) Low-temperature tempering: Put the H13 steel treated in step (3) into the heating furnace, heat it up to 320°C with the furnace, keep it warm for 2 hours, and cool it to room temperature in air to complete one tempering, and repeat this step twice , a total of three tempering.

After pretreatment and three tempering treatments, samples were taken from the center of the H13 steel plate, and after mechanical grinding and polishing, 4% nitric acid alcohol was used to corrode, and the transverse structure was observed. The structure was uniform and fine, and the carbides were dispersed. The average heat treatment hardness is 53.8HRC, and the average V-port Charpy impact energy is 10.2J.

Example 6

The 60mm thick H13 steel plate is selected, and the specific heat treatment process is as follows:

(1) High-temperature quenching: put the H13 steel shear blade blank into the heating furnace, heat it to 840°C with the furnace, keep it for 50 minutes, continue to heat up to 1095°C, keep it for 30 minutes, and cool it with air or oil to ≤100°C;

(2) High-temperature tempering: put the H13 steel treated in step (1) into the heating furnace, heat it to 800°C with the furnace, keep it for 2 hours, and air-cool it to room temperature after taking it out of the furnace to complete the pretreatment process;

(3) Vacuum quenching: Roughly process the H13 steel treated in step (2), put it into a vacuum heating furnace, heat up to 1050 °C with the furnace, keep it for 40 minutes, and cool it out of the furnace to ≤100 °C with air or oil;

(4) Low-temperature tempering: Put the H13 steel treated in step (3) into the heating furnace, heat it up to 330°C with the furnace, keep it warm for 2.5 hours, and cool it to room temperature in air to complete one tempering, and repeat this step for two more times. times, a total of three tempering.

After pretreatment and three tempering treatments, samples were taken from the center of the H13 steel plate, and after mechanical grinding and polishing, 4% nitric acid alcohol was used to corrode, and the transverse structure was observed. The structure was uniform and fine, and the carbides were dispersed. The average heat treatment hardness is 53.5HRC, and the average V-port Charpy impact energy is 10.5J.

Example 7

The 65mm thick H13 steel plate is selected, and the specific heat treatment process is as follows:

(1) High-temperature quenching: put the H13 steel shear blade blank into the heating furnace, heat it to 840°C with the furnace, keep it for 1h, continue to heat up to 1100°C, keep it for 35min, and cool it out of the furnace by air or oil to ≤100°C;

(2) High-temperature tempering: put the H13 steel treated in step (1) into the heating furnace, heat it to 820°C with the furnace, keep it for 2.5 hours, and air-cool it to room temperature after taking it out of the furnace to complete the pretreatment process;

(3) Vacuum quenching: Roughly process the H13 steel treated in step (2), put it into a vacuum heating furnace, heat up to 1060 °C with the furnace, keep it for 35 minutes, and cool it out of the furnace to ≤100 °C with air or oil;

(4) Low-temperature tempering: Put the H13 steel treated in step (3) into the heating furnace, heat it up to 340°C with the furnace, keep it warm for 2 hours, and cool it to room temperature in air to complete one tempering, and repeat this step twice , a total of three tempering.

After pretreatment and three tempering treatments, samples were taken from the center of the H13 steel plate, and after mechanical grinding and polishing, 4% nitric acid alcohol was used to corrode, and the transverse structure was observed. The structure was uniform and fine, and the carbides were dispersed. The average heat treatment hardness is 52.6HRC, and the average V-port Charpy impact energy is 11.0J.

Example 8

The 70mm thick H13 steel plate is selected, and the specific heat treatment process is as follows:

(1) High-temperature quenching: put the H13 steel shear blade blank into the heating furnace, heat it to 850°C with the furnace, keep it for 50 minutes, continue to heat up to 1100°C, keep it for 35 minutes, and cool it out of the furnace by air or oil to ≤100°C;

(2) High-temperature tempering: put the H13 steel treated in step (1) into the heating furnace, heat it to 820°C with the furnace, keep it for 2 hours, and air-cool it to room temperature after taking it out of the furnace to complete the pretreatment process;

(3) Vacuum quenching: Roughly process the H13 steel treated in step (2), put it into a vacuum heating furnace, heat up to 1060°C with the furnace, keep it warm for 40 minutes, and cool it out of the furnace to ≤100°C with air or oil;

(4) Low-temperature tempering: Put the H13 steel treated in step (3) into the heating furnace, heat it up to 350°C with the furnace, keep it warm for 2 hours, and cool it to room temperature in air to complete one tempering, and then repeat this step twice , a total of three tempering.

After pretreatment and three tempering treatments, samples were taken from the center of the H13 steel plate, and after mechanical grinding and polishing, 4% nitric acid alcohol was used to corrode, and the transverse structure was observed. The structure was uniform and fine, and the carbides were dispersed. The average heat treatment hardness is 52.1HRC, and the average V-port Charpy impact energy is 11.7J.

Claims (5)

1. A heat treatment process for improving the strength and toughness of H13 steel for hot-rolled shear blades, characterized in that, the thickness of H13 steel for said hot-rolled shear blades is 35 to 70 mm, and its heat treatment process includes high-temperature quenching, high-temperature tempering, and vacuum quenching , Low temperature tempering four steps, the specific process is as follows: (1) High-temperature quenching: put the H13 steel into the heating furnace, heat it to 1080-1100 ° C with the furnace, keep it warm for 25-35 minutes, and cool it out of the furnace with air or oil; (2) High-temperature tempering: put the H13 steel treated in step (1) into the heating furnace, heat it to 780-820°C with the furnace, keep it warm for 2-2.5 hours, and then take it out of the furnace and air-cool it to room temperature; (3) Vacuum quenching: Roughly process the H13 steel treated in step (2), put it into a vacuum heating furnace, heat it to 1040-1060°C with the furnace, keep it warm for 30-40 minutes, and cool it out of the furnace with air or oil; (4) Low-temperature tempering: put the H13 steel treated in step (3) into the heating furnace, heat it to 300-350°C with the furnace, keep it warm for 2-2.5 hours, and cool it to room temperature in air, that is, complete one tempering, and repeat this process The steps are operated twice, and tempering is carried out three times in total to complete the heat treatment process. 2. The heat treatment process for improving the strength and toughness of H13 steel for hot-rolled shears according to claim 1, wherein the high-temperature quenching step also includes heating the H13 steel to 800-800 °C with the furnace after it is loaded into the heating furnace. 850°C, keep warm for 40-60 minutes, and then raise the temperature to 1080-1100°C for heat preservation. 3. The heat treatment process for improving the strength and toughness of H13 steel for hot-rolled shear blades according to claim 2, characterized in that, in the high-temperature quenching step, air cooling or oil cooling to ≤ 100°C is carried out. 4. The heat treatment process for improving the strength and toughness of H13 steel for hot-rolled shear blades according to claim 3, characterized in that, the step of vacuum quenching is air-cooled or oil-cooled to ≤ 100°C. 5. The heat treatment process for improving the strength and toughness of H13 steel for hot-rolled shears according to any one of claims 1-4, characterized in that the H13 steel produced by the heat treatment process is sampled at the core and processed into 10mm × 10mm × The 55mm V-notch Charpy impact specimen has been tested to have an impact energy ≥ 9.0J and a hardness of 52-56HRC.

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