Wear-resistant and low-temperature-resistant tool steel and heat treatment method

Abstract

The present invention belongs to the field of metal materials technology, and more particularly relates to a wear-resistant and low-temperature-resistant steel for cutting tools and a heat treatment method. The steel's chemical composition by weight is as follows: C: 0.30%-0.40%, Si: 0.25%-0.30%, Mn: 0.50%-0.60%, P≤0.010, S≤0.015, Cr: 2.00%-2.50%, Ni: 1.80%-2.90%, Mo: 0.65%-0.95%, N≤0.010%, with the remainder being Fe and unavoidable impurities. Advantages include suitability for efficient and continuous production of cutting tools, a low amount of added alloy, and a processing hardness of only 45-48 HRC after quenching and tempering heat treatment, resulting in low material and processing costs. After forming the cutting tool, heat treatment can achieve an outer layer hardness of 60-63 HRC, ensuring wear resistance while minimizing deformation.

Description

Technical Field

[0001] The invention belongs to the technical field of metal materials, and in particular relates to wear-resistant and low-temperature-resistant tool steel and a heat treatment method. Background Art

[0002] Cutting tools are widely used in industrial production, and their performance directly affects processing efficiency and workpiece quality. Traditional cutting tools are manufactured from the same material. When the hardness exceeds 55HRC, processing costs increase, and the tool life is generally reduced. Cutting tool steel is generally quenched and tempered during production. Although it has good overall performance, it lacks toughness at low temperatures and is prone to brittle fracture, limiting its application in harsh conditions. Tool steel has deficiencies in strength, wear resistance, and low-temperature resistance, making it difficult to meet the needs of high-performance cutting tools.

[0003] Prior art patent application CN202211221368.1 discloses a high-hardness, high-nitrogen martensitic stainless steel tool material and its preparation method. The chemical composition and austenite structure of the stainless steel are adjusted, and the high-nitrogen austenitic stainless steel is transformed through a solid-state phase transformation to produce martensitic stainless steel with a high nitrogen supersaturation solid solubility. A combined solution-aging-quenching heat treatment is used to adjust the composition of the austenite matrix phase. Combined with the Scheffler phase diagram, the composition is adjusted to produce dispersion-strengthened, high-strength martensite, improving the toughness of the high-hardness metal material. The overall hardness exceeds 55HRC, but the surface wear resistance does not meet the requirements of cutting tools. Patent application number CN201210442673.3 discloses a heat treatment process for high-speed steel used in cutting tools. This process replaces molybdenum with chromium, and replaces expensive cobalt with a combination of vanadium and nitrogen, thereby reducing the production cost of the alloy steel. The addition of non-carbide element nickel enhances the steel's strength through solid solution strengthening, while also providing high plasticity and toughness, and significantly increasing its hardenability. The addition of boron and titanium increases the steel's hardness and wear resistance. While the steel exhibits high hot hardness and cutting performance, along with high toughness and wear resistance, it does not mention its low-temperature performance, and its production cost is relatively high.

[0004] Therefore, developing a steel for cutting tools with low production cost, high strength, high wear resistance and excellent low temperature resistance has become an urgent problem to be solved. Summary of the Invention

[0005] In order to overcome the shortcomings of the existing technology, the purpose of the present invention is to provide a wear-resistant and low-temperature resistant tool steel and a heat treatment method to meet the needs of high strength, high wear resistance and low-temperature resistance of cutting tools. Through the design of chemical composition and staged heat treatment, the core and surface of the same material can have different mechanical properties, ensuring that the tool steel uses good low-temperature toughness as an effective support for the blade during use, and the high wear resistance and high hardness properties of the surface meet the needs of high-load cutting.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A wear-resistant and low-temperature resistant steel for cutting tools, wherein the chemical composition by weight of the steel is:

[0008] C: 0.30%~0.40%, Si: 0.25%~0.30%, Mn: 0.50%~0.60%, P≤0.010, S≤0.015, Cr: 2.00%~2.50%, Ni: 1.80%~2.90%, Mo: 0.65%~0.95%, N≤0.010%, and the rest are Fe and unavoidable impurities.

[0009] The present invention selects the above alloying element types and contents because of the role of each element in wear-resistant and low-temperature resistant tool steel:

[0010] C is an important element for precipitation strengthening and carbide-based martensite formation. Therefore, to achieve these effects, 0.30% or more C is required. Surface induction hardening induces stronger structural stresses, and excessive C-formed martensite can cause blade dimensional changes and susceptibility to cracking during hardening. Therefore, the upper limit of C is set at 0.40%.

[0011] Si can be added as a deoxidizing element during production. Si exerts a solid solution strengthening effect on ferrite, and to achieve this effect, a content of 0.25% or more is required. If Si exceeds 0.30%, the alloy's tempering resistance increases and the low-temperature brittle phase becomes more susceptible to precipitation. Therefore, the upper limit of Si is set to 0.30%.

[0012] Mn, like Si, has a deoxidizing effect and can be added during manufacturing. Mn also increases hardenability and proper addition can improve hardening properties.

[0013] The appropriate addition of Cr increases strength and wear resistance and reduces decarburization during heat treatment. However, like Ni, Cr also lowers the martensitic transformation temperature. Excessive Cr addition increases the amount of retained austenite, leading to lower strength. Therefore, the upper limit is set at 2.5%.

[0014] Nickel, dissolved in the matrix, contributes to the material's solid solution strengthening and hardenability, increasing steel strength without compromising toughness. It also helps improve low-temperature toughness and fatigue resistance. When combined with Cr and Mo, nickel particularly enhances hardenability after quenching and tempering, facilitating austenitization during surface quenching in a short period of time. Nickel-molybdenum steel also has a very high fatigue limit. Furthermore, nickel inhibits grain growth at high temperatures, maintaining a fine-grained structure. Therefore, the upper limit of nickel addition is 2.9%.

[0015] Mo in quenched and tempered steel can improve the steel's tempering resistance or tempering stability, allowing parts to reduce crack sensitivity at higher surface temperatures, thereby more effectively adapting to the surface quenching process; molybdenum can also maintain a relatively stable hardness of the steel, increase resistance to deformation, cracking and wear, and improve service life.

[0016] The balance is Fe and impurity elements that inevitably enter during manufacturing. Typical impurity elements include S, P, and N. Ideally, the amount of these elements should be as low as possible during manufacturing using standard equipment. The lower the amount of each element, the better.

[0017] The processing hardness of the steel is 45-48HRC, and the hardness of the outer layer of the tool formed from the steel is 60-63HRC.

[0018] A heat treatment method for wear-resistant and low-temperature-resistant tool steel comprises the following steps:

[0019] 1) Quenching and tempering heat treatment: quenching + tempering treatment is adopted, the quenching heating temperature is 870~890℃, the quenching medium is quenching oil, after keeping warm until it is completely austenitized, quenching and rapid cooling to below 50℃ with quenching oil; the tool steel matrix after quenching is tempered at 520~600℃, kept warm for 2~4h, and then water-cooled or air-cooled to room temperature, and the structure is tempered bainite;

[0020] 2) Process heat treatment: The machined tool is quenched using ultra-high frequency induction heating. The surface quenching time is 1 to 20 seconds. Quenching oil is used for quenching, and the structure is cryptocrystalline martensite. Then, low-temperature tempering is performed at a tempering temperature of 180°C to 200°C. After keeping warm for 2 to 4 hours, air cooling is performed to room temperature for stress relief.

[0021] The step 1) obtains a tool steel substrate having a yield strength of 1590-1630 MPa, a tensile strength of 1660-1871 MPa, and a hardness of 45-48 HRC, while maintaining a toughness state with a low-temperature impact energy KV2 of 66-89 J at -20°C.

[0022] The thickness of the quenching layer in step 2) is 1 mm to 3 mm.

[0023] Step 2) The surface yield strength of the tool is obtained to be 1200-1350 MPa, the tensile strength is 2136-2290 MPa, the hardness is 60-63 HRC, and the low-temperature impact energy KV2 at -20°C is maintained at 7-19 J.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The steel alloy of this invention is suitable for the efficient and continuous production of cutting tools. The amount of alloy added is relatively low, and the material is processed on a quenched and heat-treated substrate to a hardness of only 45-48 HRC, resulting in low material and processing costs. After the cutting tools are machined and formed, heat treatment is performed to achieve an outer layer hardness of 60-63 HRC, ensuring wear resistance while minimizing deformation. In terms of material quality, this cutting tool steel has a material hardness comparable to high-hardness alloy steels such as H13 and SKH9, but far surpasses them in wear resistance, low-temperature resistance, and fatigue resistance.

[0026] Through chemical composition design and specific heat treatment, this invention effectively achieves high hardness and fatigue resistance in tool steel while also meeting the economic requirements of tool manufacturing. In terms of economic benefits, the addition of low amounts of alloy reduces smelting costs. While machining hard materials is expensive, this material, formed at a low hardness and then surface treated, reduces both processing difficulty and economic costs. Furthermore, the toughness of the matrix and transition section prevents the tool from breaking, extending its service life. Furthermore, the high hardness and wear resistance of the surface layer also extend the tool's service life. DETAILED DESCRIPTION

[0027] The present invention will be described in detail below, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0028] The present invention can effectively realize wear-resistant and low-temperature-resistant tool steel through chemical composition design and specific heat treatment, meet the requirements of cutting tool indicators, and obtain more significant wear resistance, toughness and economy than ordinary quenching + tempering alloy steel.

[0029] A wear-resistant and low-temperature-resistant tool steel, the chemical composition weight percentage of which is:

[0030] C: 0.30%~0.40%, Si: 0.25%~0.30%, Mn: 0.50%~0.60%, P≤0.010, S≤0.015, Cr: 2.00%~2.50%, Ni: 1.80%~2.90%, Mo: 0.65%~0.95%, N≤0.010%, and the rest are Fe and unavoidable impurities.

[0031] The processing hardness of the steel for the tool is 45-48HRC, and the hardness of the outer layer of the tool formed from the steel is 60-63HRC.

[0032] The steel material for quenching and tempering heat treatment is not particularly limited in terms of the smelting method, forging, rolling process, and rough processing shape before the final processing of the steel billet. In practice, wear-resistant and low-temperature resistant steel for cutters achieves wear resistance and low-temperature resistance by adopting quenching and tempering heat treatment + process treatment. Quenching and tempering heat treatment is a heat treatment for unprocessed steel, and the structure and hardness obtained by quenching and tempering serve as the toughness matrix of the cutter. Process treatment heat treatment is a surface heat treatment of the processed cutter. Specifically, it includes the following steps:

[0033] 1) Quenching and tempering heat treatment: quenching + tempering treatment is adopted, the quenching heating temperature is 870~890℃, the quenching medium is quenching oil, the holding time is 2.3~2.6min / mm, after complete austenitization, quenching oil is used to quench and rapidly cool to below 50℃; the tool steel matrix after quenching is tempered at 520~600℃, kept at this temperature for 2~4h, and then water-cooled or air-cooled to room temperature, and the structure is tempered bainite;

[0034] Through quenching and tempering heat treatment, the tool steel has a high-strength matrix hardness. The matrix strength reaches a yield strength of 1590~1630MPa, a tensile strength of 1660~1871MPa, and a hardness of 45~48HRC. During the use of the tool, it has the function of supporting the tool body firmly and not easy to deform. After quenching and tempering, the matrix has low crack sensitivity to drastic temperature changes on the surface and maintains a toughness state of 66~89J of low-temperature impact energy KV2 at -20℃. At this time, the tool steel has high hardness and fatigue resistance while taking into account the low-temperature toughness requirements of the tool.

[0035] 2) Process Heat Treatment: The machined tool is quenched using ultra-high frequency induction heating. After surface quenching completes austenitization within 1-20 seconds, it is then quenched with quenching oil to a microstructure of cryptocrystalline martensite. The surface quenched layer reaches a thickness of 1mm-3mm. Low-temperature tempering is then performed at 180°C. After holding for 2-4 hours, it is air-cooled to room temperature, resulting in a microstructure of tempered martensite. Surface quenching thermally affects the matrix structure but does not completely austenitize it. The resulting transitional structure gradually changes in hardness. The holding time is adjusted based on the blade thickness, resulting in a small hardness gradient between the surface and the matrix.

[0036] Through process heat treatment, the processed low-alloy cutting tools can obtain higher surface hardness, with the surface strength reaching a yield strength of 1200~1350MPa, a tensile strength of 2136~2290MPa, and a hardness of 60~63HRC. During the use of the tool, it has good cutting performance, small deformation, and maintains a low-temperature impact energy KV2 of 7~19J at -20℃. At this time, due to the rapid cooling of the tool steel surface to produce cryptocrystalline martensite, the hardness and toughness are better than those of conventional acicular martensite, which improves the wear resistance and low-temperature resistance of the tool and increases the service life requirements.

[0037] Example 1

[0038] A 21-ton steel ingot produced by continuous casting and electroslag remelting was rolled into 30-mm-thick steel plates to serve as tool blanks. The composition of the steel ingot is shown in Table 1.

[0039] Table 1 Blank composition (mass %)

[0040]

[0041] The steel plates were cut into 30×70×250 mm tool blanks and subjected to quenching and tempering heat treatment. The steel plates were quenched in a box-type resistance furnace, heated to 890°C for 1 hour, and then quenched with oil as the medium. The quenched steel plates were then subjected to high-temperature tempering at 590°C for 4 hours, followed by water cooling to room temperature. The steel blanks were then cut and subjected to mechanical property testing. The results are summarized in Table 2. The quenched and tempered steel plates were then finished into tool blanks and subjected to process heat treatment. The blades to be quenched were heated in an ultra-high frequency coil for 4 seconds, then quenched and cooled to room temperature using quenching oil. The blades were then subjected to low-temperature tempering at 180°C for 2 hours. Hardness testing revealed a hardened layer thickness of 1.1 mm. Test specimens were cut from the tool, surface quenched for 20 seconds, and then subjected to mechanical property testing. The surface hardness of the specimens was consistent with that of the tool. The results are summarized in Table 3. The average temperature during winter testing was -10°C to -24°C, and the cutting tool was tested for 42,000 cuts, exceeding the lifespan requirement of 30,000 cuts.

[0042] Table 2 Mechanical properties of quenching and tempering heat treatment

[0043]

[0044] Table 3 Mechanical properties of heat treatment process

[0045]

[0046] As shown in the above results, it can be seen that the application of the composition of Example 1 and the staged heat treatment effectively achieves the index requirements of high hardness, wear resistance and low temperature resistance of the material.

[0047] Example 2

[0048] An 11-ton die-cast steel ingot was hot-forged into a 50 × 170 × 260 mm bar to serve as the tool blank. The composition of the ingot is shown in Table 4.

[0049] Table 4 Billet composition (mass %)

[0050]

[0051] The steel plates were cut into 24×60×210 mm tool blanks and subjected to quenching and tempering heat treatment. The steel plates were quenched in a box-type resistance furnace, heated to 880°C for 1 hour, and then quenched with oil. The quenched steel plates were then subjected to high-temperature tempering at 600°C, held for 2 hours, and then water-cooled to room temperature. The steel blanks were then cut and mechanically tested. The results are shown in Table 5. The quenched and tempered steel plates were then finished into tool blanks and subjected to process heat treatment. The tool blanks were induction-heated using an ultra-high frequency coil. The tool blanks were placed in the coil for 3 seconds, then quenched and cooled to room temperature. The quenching medium was quenching oil. The tool blanks were then subjected to low-temperature tempering at 180°C for 2 hours. Hardness testing was performed, and the blade hardened layer thickness was 1.0 mm. Test specimens were cut from the tool blanks, surface-quenched for 20 seconds, and then mechanically tested. The surface hardness of the specimens was consistent with that of the tool blanks. A summary of the results is shown in Table 6. The average temperature during winter testing was -10°C to -24°C, and the cutting tool was tested 47,000 times, exceeding the lifespan requirement of 30,000 times.

[0052] Table 5 Mechanical properties of quenching and tempering heat treatment

[0053]

[0054] Table 6 Mechanical properties of heat treatment process

[0055]

[0056] As shown in the above results, it can be seen that the application of the composition of Example 2 and the staged heat treatment effectively achieves high hardness and high wear resistance of the material and meets the low temperature resistance index requirements.

[0057] Example 3

[0058] An 11-ton die-cast steel ingot was hot-forged into a 50 × 170 × 260 mm bar to serve as the tool blank. The composition of the ingot is shown in Table 7.

[0059] Table 7 Blank composition (mass %)

[0060]

[0061] The steel plate was cut into 38×90×210mm tool blanks and subjected to quenching and tempering heat treatment. The steel plate was quenched in a box-type resistance furnace, and the steel plate was heated to 890℃ and held for 1 hour. The medium was quenching oil. The quenched steel plate was subjected to high-temperature tempering treatment. The tempering temperature was 590℃ and then water-cooled to room temperature. The steel plate was then cut and mechanical properties tested. The test results are shown in Table 8. The steel plate that completed the quenching and tempering heat treatment was fine-processed into a tool and then subjected to process heat treatment. The tool was quenched and heated using an ultra-high frequency coil. The tool was placed in the coil for induction heating. After holding for 4 seconds, it was quenched and cooled to room temperature. The quenching medium was quenching oil. It was then subjected to low-temperature tempering at a holding temperature of 180℃ for 2 hours. The hardness test showed that the thickness of the blade hardened layer was 1.08mm. The tool was cut into test pieces, surface-quenched for 20 seconds, and then mechanical properties tested. The surface hardness of the test piece was consistent with that of the tool. The test results are shown in Table 9. The average temperature during winter testing was -10°C to -24°C, and the cutting tool was tested 49,000 times, exceeding the lifespan requirement of 30,000 times.

[0062] Table 8 Mechanical properties of quenching and tempering heat treatment

[0063]

[0064] Table 9 Mechanical properties of heat treatment process

[0065]

[0066] As shown in the above results, it can be seen that the application of the composition of Example 3 and the staged heat treatment effectively achieves high hardness and high wear resistance of the material and meets the low temperature resistance index requirements.

[0067] Example 4

[0068] An 11-ton die-cast steel ingot was hot-forged into a 50 × 170 × 260 mm bar to serve as the tool blank. The composition of the ingot is shown in Table 10.

[0069] Table 10 Billet composition (mass %)

[0070]

[0071] The steel plates were cut into 38×90×210 mm tool blanks and subjected to quenching and tempering heat treatment. The steel plates were quenched in a box-type resistance furnace, heated to 880°C for 1 hour, then quenched with oil as the medium. The quenched steel plates were then subjected to high-temperature tempering at 550°C for 2 hours, then water-cooled to room temperature. The steel blanks were then cut and mechanically tested. The test results are summarized in Table 11. The quenched and tempered steel plates were then finished into tool blanks and subjected to process heat treatment. The tool blanks were induction-heated using an ultra-high frequency coil. The tool blanks were placed in the coil for 5 seconds, then quenched and cooled to room temperature using quenching oil as the medium. The tool blanks were then subjected to low-temperature tempering at 180°C for 2 hours. Hardness testing was performed, and the blade hardened layer thickness was 1.5 mm. Test specimens were cut from the tool blanks, surface-quenched for 20 seconds, and then mechanically tested. The surface hardness of the specimens was consistent with that of the tool blanks. A summary of the results is shown in Table 12. The average temperature during winter testing was -10°C to -24°C, and the cutting tool was tested 48,000 times, exceeding the lifespan requirement of 30,000 times.

[0072] Table 11 Mechanical properties of quenching and tempering heat treatment

[0073]

[0074] Table 12 Mechanical properties of heat treatment process

[0075]

[0076] As shown in the above results, it can be seen that the application of the composition of Example 4 and the staged heat treatment effectively achieves high hardness and high wear resistance of the material and meets the low temperature resistance index requirements.

[0077] Example 5

[0078] The die-cast steel ingots were hot forged into bars measuring 50 × 170 × 260 mm to serve as tool blanks. The composition of the steel ingots is shown in Table 13.

[0079] Table 13 Blank composition (mass %)

[0080]

[0081] The steel plates were cut into 38×90×210 mm tool blanks and subjected to quenching and tempering heat treatment. The steel plates were quenched in a box-type resistance furnace, heated to 890°C and held for 1 hour. The quenching medium was oil. The quenched steel plates were then subjected to high-temperature tempering at 600°C, held for 2 hours, and then water-cooled to room temperature. The steel blanks were then cut and mechanically tested. The test results are summarized in Table 14. The quenched and tempered steel plates were then finished into tool blanks and subjected to process heat treatment. The tool blanks were induction-heated using an ultra-high frequency coil. The tool blanks were placed in the coil for induction heating, held for 5 seconds, and then quenched and cooled to room temperature. The quenching medium was quenching oil. The tool blanks were then subjected to low-temperature tempering at 180°C for 2 hours. Hardness testing was performed, and the blade hardened layer thickness was 1.5 mm. Test specimens were cut from the tool blanks, surface-quenched for 20 seconds, and then mechanically tested. The surface hardness of the specimens was consistent with that of the tool blanks. A summary of the results is shown in Table 15. The average temperature during winter testing was -10°C to -24°C, and the cutting tool was tested 48,000 times, exceeding the lifespan requirement of 30,000 times.

[0082] Table 14 Mechanical properties of quenching and tempering heat treatment

[0083]

[0084] Table 15 Mechanical properties of heat treatment process

[0085]

[0086] As shown in the above results, it can be seen that the application of the composition of Example 5 and the staged heat treatment effectively achieves high hardness and high wear resistance of the material and meets the low temperature resistance index requirements.

Claims

1. A wear-resistant and low-temperature resistant tool steel, characterized in that: The chemical composition weight percentage of the steel is: C: 0.30%~0.40%, Si: 0.25%~0.30%, Mn: 0.50%~0.60%, P≤0.010, S≤0.015, Cr: 2.00%~2.50%, Ni: 1.80%~2.90%, Mo: 0.65%~0.95%, N≤0.010%, the rest is Fe and unavoidable impurities; The processing hardness of the steel is 45-48HRC, and the hardness of the outer layer of the tool formed from the steel is 60-63HRC; The heat treatment method for wear-resistant and low-temperature-resistant tool steel comprises the following steps: 1) Quenching and tempering heat treatment: quenching + tempering treatment is adopted, the quenching heating temperature is 870~890℃, the quenching medium is quenching oil, after keeping warm until it is completely austenitized, quenching and rapid cooling to below 50℃ with quenching oil; the tool steel matrix after quenching is tempered at 520~600℃, kept warm for 2~4h, and then water-cooled or air-cooled to room temperature, and the structure is tempered bainite; 2) Process heat treatment: The machined tool is quenched using ultra-high frequency induction heating. The surface quenching time is 1 to 20 seconds. Quenching oil is used for quenching, and the structure is cryptocrystalline martensite. Then, low-temperature tempering is performed at a tempering temperature of 180°C to 200°C. After keeping warm for 2 to 4 hours, air cooling is performed to room temperature for stress relief.

2. A heat treatment method for wear-resistant and low-temperature-resistant tool steel according to claim 1, characterized in that: The following steps are involved: 1) Quenching and tempering heat treatment: quenching + tempering treatment is adopted, the quenching heating temperature is 870~890℃, the quenching medium is quenching oil, after keeping warm until it is completely austenitized, quenching and rapid cooling to below 50℃ with quenching oil; the tool steel matrix after quenching is tempered at 520~600℃, kept warm for 2~4h, and then water-cooled or air-cooled to room temperature, and the structure is tempered bainite; 2) Process heat treatment: The machined tool is quenched using ultra-high frequency induction heating. The surface quenching time is 1 to 20 seconds. Quenching oil is used for quenching, and the structure is cryptocrystalline martensite. Then, low-temperature tempering is performed at a tempering temperature of 180°C to 200°C. After keeping warm for 2 to 4 hours, air cooling is performed to room temperature for stress relief.

3. The heat treatment method for wear-resistant and low-temperature-resistant tool steel according to claim 2, characterized in that: The step 1) obtains a tool steel substrate having a yield strength of 1590-1630 MPa, a tensile strength of 1660-1871 MPa, and a hardness of 45-48 HRC, while maintaining a toughness state with a low-temperature impact energy KV2 of 66-89 J at -20°C.

4. The heat treatment method for wear-resistant and low-temperature-resistant tool steel according to claim 2, characterized in that: The holding time in step 1) is 2.2 min / mm to 2.5 min / mm.

5. The heat treatment method for wear-resistant and low-temperature-resistant tool steel according to claim 2, characterized in that: The thickness of the quenching layer in step 2) is 1 mm to 3 mm.

6. The heat treatment method for wear-resistant and low-temperature-resistant tool steel according to claim 2, characterized in that: In the step 2), the surface yield strength of the tool is 1200-1350 MPa, the tensile strength is 2136-2290 MPa, the hardness is 60-63 HRC, and the low-temperature impact energy KV2 at -20°C is maintained at 7-19 J.

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