A nitrogen distribution-strengthened high-hardness, high-wear-resistant and corrosion-resistant steel and a preparation method thereof

Abstract

The present invention discloses a nitrogen distribution type strengthened high hardness high wear and corrosion resistant steel and a preparation method thereof, which belongs to the technical field of tool steel, and solves the problem that the hardness, corrosion resistance and wear resistance of corrosion resistant plastic mold steel in the prior art cannot be taken into account at the same time. The components of the nitrogen distribution type strengthened high hardness high wear and corrosion resistant steel include, by mass percentage: C: 0.25% to 0.50%, Si: ≤1%, Mn: ≤1%, Cr: 15.0% to 20.0%, Ni: 0.005% to 2.0%, Mo: 0.9% to 3.0%, V: ≤0.20%, N: 0.35% to 0.60%, and the balance is Fe and unavoidable impurities. The nitrogen distribution type strengthened high hardness high wear and corrosion resistant steel of the present invention has excellent mechanical properties and corrosion resistance.

Description

Technical Field

[0001] The invention belongs to the field of tool steel, and particularly relates to a Cr-Ni-Mo-N composite alloyed, nitrogen-distributed reinforced, high-hardness, high-wear-resistant, and corrosion-resistant steel with excellent comprehensive performance and a preparation method thereof. Background Art

[0002] As a high-end product among mold steels, corrosion-resistant plastic mold steel is mainly used for special engineering plastics with high forming temperatures and plastics containing flame retardants. The raw material will decompose in a molten state to produce a large amount of corrosive gases, such as hydrogen chloride, hydrogen fluoride and sulfur dioxide, which will corrode the plastic mold cavity used, resulting in a reduction in the service life of the mold. Therefore, such molds should have certain corrosion resistance. As the beneficial effect of cheap nitrogen on the performance of steel becomes increasingly significant, the addition of nitrogen to plastic mold steel has begun to receive attention and development. The addition of nitrogen will not only not affect the other properties of stainless steel, but also partially replace expensive Ni and other alloying elements to improve the corrosion resistance of mold steel. Commonly used corrosion-resistant plastic mold steels are 4Cr13, 9Cr18, etc., which belong to martensitic stainless steels. However, most of these steels currently have problems such as severe carbide segregation, poor microstructure uniformity, and insufficient corrosion resistance, which restricts the quality stabilization and high-end market of this type of steel, and its performance needs to be further improved. Summary of the invention

[0003] In view of the above situation, the present invention aims to provide a nitrogen distribution strengthened high hardness high wear and corrosion resistant steel and a preparation method thereof, which is used to solve the problems of severe carbide segregation and poor organizational uniformity in the existing high nitrogen corrosion resistant plastic mold steel; and the problems that hardness, corrosion resistance and wear resistance cannot be taken into account at the same time.

[0004] The purpose of the present invention is mainly achieved through the following technical solutions:

[0005] The invention provides a nitrogen distribution-strengthened high-hardness, high-wear-resistant and corrosion-resistant steel. The components of the nitrogen distribution-strengthened high-hardness, high-wear-resistant and corrosion-resistant steel include, by mass percentage: C: 0.25%-0.50%, Si: ≤1%, Mn: ≤1%, Cr: 15.0%-20.0%, Ni: 0.005%-2.0%, Mo: 0.9%-3.0%, V: ≤0.20%, N: 0.35%-0.60%, and the balance is Fe and unavoidable impurities.

[0006] Furthermore, the components of the nitrogen distribution-strengthened high-hardness, high-wear-resistant and corrosion-resistant steel are also added with one or more of the following elements, in percentage by mass: W≤0.5%, Cu≤0.5%, Nb≤0.05%, Co≤0.5%, and rare earth elements≤0.05%.

[0007] Furthermore, the components of the nitrogen distribution strengthened high hardness, high wear and corrosion resistant steel include, by mass percentage: C: 0.26%~0.49%, Si: 0.3%~0.9%, Mn: 0.25%~0.9%, Cr: 15.2%~20.0%, Ni: 0.006%~2.0%, Mo: 0.95%~3.0%, V: ≤0.20%, N: 0.35%~0.60%, and the balance is Fe and unavoidable impurities.

[0008] The present invention also provides a method for preparing nitrogen distribution-strengthened high-hardness, high-wear-resistant and corrosion-resistant steel, which is used to prepare the above-mentioned nitrogen distribution-strengthened high-hardness, high-wear-resistant and corrosion-resistant steel, comprising:

[0009] Step 1, smelting and casting to obtain an electrode blank, and subjecting the electrode blank to slow cooling or heat preservation annealing treatment;

[0010] Step 2, remelting the electrode blank in a pressurized electroslag furnace, casting it into a steel ingot, and subjecting the steel ingot to slow cooling or heat preservation annealing treatment;

[0011] Step 3, forging the steel ingot to obtain a forging blank;

[0012] Step 4, dispersing the forging blank;

[0013] Step 5, annealing the steel after dispersion treatment;

[0014] Step 6: quench the annealed steel, then perform deep cooling treatment, and then perform tempering treatment.

[0015] Furthermore, in step 3, forging includes: fully heating the steel ingot and keeping it warm before forging; the heating temperature is controlled at 1160-1200° C., and the keeping time is 10-15 hours.

[0016] Furthermore, in step 3, the initial forging temperature is 1150-1200°C, and the final forging temperature is 830-860°C.

[0017] Furthermore, in step 4, the dispersion treatment includes: heating the forging blank to a first holding temperature of 960-1020°C for 1-2 hours, and then water cooling to room temperature; then keeping it at a second holding temperature of 620-680°C for 2-4 hours, and air cooling to room temperature.

[0018] Furthermore, in step 5, the annealing treatment includes: heating the steel after dispersion treatment to 850±10°C, keeping it warm for 1 to 2 hours; furnace cooling to 650±10°C, keeping it warm for 1 to 2 hours, and then furnace cooling to below 400°C before taking it out of the furnace.

[0019] Furthermore, in step 6, the quenching treatment includes: keeping the temperature at 950-1050° C. for 0.5-2 h, and cooling the product to room temperature by water or oil after it is taken out of the furnace.

[0020] Furthermore, in step 6, the cryogenic treatment includes: keeping warm at -73°C to -84°C for 0.5 to 2 hours, and air cooling to room temperature.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] a) The high-hardness, high-wear-resistant and corrosion-resistant steel of the present invention obtains martensite and fine dispersed precipitation phases by adding appropriate amounts of Cr, Ni, Mo and N elements under appropriate dispersion treatment and quenching + deep cooling + tempering processes, thereby obtaining higher strength and hardness.

[0023] b) The high-hardness, high-wear-resistant and corrosion-resistant steel of the present invention obtains good impact toughness and reduces element and tissue segregation through the alloying design of Cr-Ni-Mo-N composite alloying; higher strength and hardness are obtained by nitrogen element distribution strengthening technology, thereby obtaining good wear resistance; the Mo-Ni composite corrosion resistance treatment of the present invention, and through reasonable element matching, through the dispersion treatment preparation process and appropriate heat treatment process, obtains more excellent corrosion resistance.

[0024] c) The high-hardness, high-wear-resistant and corrosion-resistant steel prepared by the composition and method of the present invention has good comprehensive mechanical properties. The steel after low-temperature tempering can reach a room temperature hardness ≥ 56HRC. There are hard carbides and carbonitride precipitation phases that can resist wear, which play a dual strengthening role of solid solution strengthening and precipitation strengthening. While the hardness is high, it can also enhance the wear resistance. After high-temperature tempering, the steel can have higher impact toughness and tensile strength, for example, impact toughness Ak ≥ 460J, and tensile strength ≥ 1040MPa. At the same time, the corrosion resistance is excellent, and the corrosion rate is 0.012g / m 2 ·h or less.

[0025] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0027] Figure 1 This is a grain size diagram of the steel after quenching according to Example 2 of the present invention;

[0028] Figure 2 This is a grain size diagram of the steel after quenching according to Example 2 of the present invention;

[0029] Figure 3 This is the grain size diagram of the steel in comparative example 1 after quenching;

[0030] Figure 4 This is the grain size diagram of the steel in comparative example 1 after quenching;

[0031] Figure 5 This is a low temperature tempering structure diagram of Example 4 of the present invention;

[0032] Figure 6 This is a high temperature tempering structure diagram of Example 4 of the present invention;

[0033] Figure 7 This is a low temperature tempering SEM image of Example 4 of the present invention;

[0034] Figure 8 This is the high temperature tempering SEM image of Example 4 of the present invention.

[0035] Fig. 9 This is the low temperature tempering structure diagram of Comparative Example 1;

[0036] Fig.10 This is the high temperature tempering organization diagram of Comparative Example 1;

[0037] Fig.11 This is the low temperature tempering SEM image of Comparative Example 1;

[0038] Fig.12 This is the high temperature tempering SEM image of Comparative Example 1. DETAILED DESCRIPTION

[0039] Preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used to explain the principles of the present invention together with the embodiments of the present invention.

[0040] The invention provides a nitrogen distribution-strengthened high-hardness, high-wear-resistant and corrosion-resistant steel. The components of the high-hardness, high-wear-resistant and corrosion-resistant steel include, by mass percentage: C: 0.25%-0.50%, Si: ≤1%, Mn: ≤1%, Cr: 15.0%-20.0%, Ni: 0.005%-2.0%, Mo: 0.9%-3.0%, V: ≤0.20%, N: 0.35%-0.60%, and the balance is Fe and unavoidable impurities.

[0041] The following is a detailed description of the effects and dosage of the components in the present invention:

[0042] C: The carbon content in steel determines the matrix hardness of the steel. For tool steel, part of the carbon dissolves into the matrix to play a role in solid solution strengthening, and the other part of the carbon combines with strong carbide-forming elements to form alloy carbides. C forms alloy carbides with some alloy elements to improve the hardness and wear resistance of the steel, and the uniformly dispersed alloy carbides and tempered martensite structure affect the corrosion resistance of the steel. In order to obtain higher hardness, wear resistance and corrosion resistance, the carbon content is controlled at 0.25% to 0.50% in the present invention.

[0043] Si: Silicon is added as a reducing agent and deoxidizer in the steelmaking process, and has a significant effect on improving corrosion resistance. However, too high Si content will not only reduce the toughness of the steel, but also promote the generation of segregation. Therefore, the silicon content is controlled below 1% in the present invention.

[0044] Mn: Manganese is an element that improves the hardenability of steel, so that the core can also achieve the desired mechanical properties. An appropriate amount of manganese can also effectively improve the strength, hardness and toughness of steel, eliminate the harmful effects of sulfur and oxygen on steel, improve the hot working performance of steel, and improve the cold brittle tendency of steel. However, too high a manganese content is prone to segregation, so the Mn content in the present invention is controlled to be below 1.0%.

[0045] Ni: Nickel is an important element for improving hardenability. In some steels, it can improve the strength and toughness of steel. The addition of Ni can improve the passivation tendency of Fe-Cr alloys, and can not only improve the corrosion resistance of steel in acid and alkali media, but also have corrosion resistance to air and salt. The Ni content in the steel of the present invention is determined to be 0.005% to 2.0%.

[0046] Cr: Chromium, as the main component of corrosion-resistant steel, can not only improve the hardenability of Fe-Cr alloy, but also guarantee the corrosion resistance and rust-proofness of steel. However, too high Cr content will promote the formation of high-temperature ferrite and network carbide, affecting the performance of steel. Therefore, the present invention controls the Cr content to 15.0% to 20.0%.

[0047] Mo: Molybdenum in steel can improve the hardenability of steel. At the same time, Mo combines with C and N elements to form carbides and carbonitrides, which improves the secondary hardening ability and tempering stability of steel. Mo is also a main element for improving corrosion resistance, but too high Mo content will promote the formation of ferrite and reduce the strength and toughness of steel. The present invention controls the Mo content to 0.9% to 3.0%.

[0048] V: Vanadium can reduce the overheat sensitivity of steel. A small amount of V element can refine the grains and promote the dispersion and precipitation of carbides through proper heat treatment, which plays a role in strengthening secondary hardening. However, too high V content will increase the probability of primary carbide formation in steel and affect the toughness of steel. The present invention controls V≤0.20%.

[0049] N: Nitrogen, as an austenitizing element, can replace Ni to reduce costs, and can also improve the corrosion resistance of steel. It combines with some elements to produce nitride dispersed phases to refine grains and play a pinning role, thereby increasing the strength and hardness of steel and achieving the purpose of improving wear resistance. The present invention controls N to 0.35% to 0.60%.

[0050] P: Phosphorus forms microscopic segregation when the molten steel solidifies, and then segregates at the grain boundary when heated to the austenitizing temperature, which significantly increases the brittleness of the steel. The present invention controls the P content to be below 0.030%, and the lower the content, the better.

[0051] S: Sulfur is an inevitable impurity, forming FeS, which brings hot brittleness to the steel. The present invention controls the S content to be below 0.030%, and the lower the content, the better.

[0052] In order to further improve the comprehensive performance of the above-mentioned high hardness, high wear and corrosion resistant steel, the components of the above-mentioned high hardness, high wear and corrosion resistant steel can also be added with one or more of the following elements, in terms of mass percentage: W≤0.5%, Cu≤0.5%, Nb≤0.05%, Co≤0.5%, rare earth elements≤0.05%.

[0053] The functions and proportions of the above elements are as follows:

[0054] W: Tungsten is one of the strong carbide-forming elements, which can increase the tempering stability, red hardness and thermal strength of steel. It combines with carbon to form special carbides, which can increase the wear resistance of steel. In the present invention, tungsten is added in an amount of ≤0.5%.

[0055] Cu: Copper is an austenite-forming element that can improve corrosion resistance and cause a secondary hardening effect. However, if the copper content is too high, it will be sensitive to overheating. In the present invention, the copper content is controlled to be ≤0.5%.

[0056] Nb: Niobium can refine grains, increase grain coarsening temperature, reduce overheat sensitivity and temper brittleness of steel, and improve strength and toughness of steel under certain conditions. In the present invention, ≤0.05% niobium is added.

[0057] Co: Cobalt is an austenite-forming element that improves tempering stability. Cobalt can improve the strength of steel by solid solution strengthening, and can also promote the second phase dispersion precipitation strengthening effect to obtain ultra-high strength and good comprehensive mechanical properties. The present invention controls the cobalt content to ≤0.5%.

[0058] Rare earth elements: Rare earth elements can refine the cast structure of steel. For large-sized steel, large ingot steel ingots are required for smelting. If necessary, a small amount of rare earth elements can be added to reduce the segregation of the cast structure and obtain a uniform solidified structure. At the same time, rare earth elements can improve the plasticity and impact toughness of steel, further strengthen the beneficial effects of silicon and manganese, and enhance the oxidation resistance of the alloy. In the present invention, ≤0.05% of rare earth elements are added.

[0059] In order to further improve the comprehensive properties of the above-mentioned high hardness, high wear and corrosion resistant steel, the components of the above-mentioned high hardness, high wear and corrosion resistant steel may include, by mass percentage: C: 0.26%~0.49%, Si: 0.3%~0.9%, Mn: 0.25%~0.9%, Cr: 15.2%~20.0%, Ni: 0.006%~2.0%, Mo: 0.95%~3.0%, V: ≤0.20%, N: 0.35%~0.60%, and the balance is Fe and unavoidable impurities.

[0060] The present invention also provides a method for preparing the above-mentioned nitrogen distribution-strengthened high-hardness, high-wear-resistant and corrosion-resistant steel, comprising:

[0061] Step 1, smelting and casting to obtain an electrode blank, and subjecting the electrode blank to slow cooling or annealing at 800-900° C.;

[0062] Step 2, remelting the electrode blank in a pressurized electroslag furnace, casting it into a steel ingot, and subjecting the steel ingot to slow cooling or annealing at 800-900°C;

[0063] Step 3, forging the steel ingot to obtain a forging blank;

[0064] Step 4, dispersing the forging blank;

[0065] Step 5, annealing the steel after dispersion treatment;

[0066] Step 6: quench the annealed steel, then perform deep cooling treatment, and then perform tempering treatment.

[0067] Specifically, in the above step 1, the smelting can be carried out by a converter, an electric furnace, an induction furnace + refining outside the furnace.

[0068] Specifically, in the above step 3, forging includes: fully heating the steel ingot and keeping it warm before forging. Considering that too high a heating temperature or too long a holding time will cause the ingot to be overburned and abnormal structure will affect the subsequent processing and performance of the steel, and too high a heating temperature and too long a holding time will waste energy; too low a heating temperature or too short a holding time will not achieve the effect of homogenizing the structure and carbide, therefore, the heating temperature is controlled to 1160-1200°C and the holding time is 10-15h.

[0069] Specifically, in the above step 3, considering that too high initial forging temperature may cause overburning and overheating, too low initial forging temperature will shorten the forging operation time, narrow the forging temperature range, and cause forging difficulties; if the final forging temperature is too high, the grains will grow rapidly at high temperature after forging, resulting in coarse grains of the forgings and reduced mechanical properties of the forgings, while if the final forging temperature is too low, the forgings will have poor plasticity, difficult deformation, increased internal stress, and cracks in the forgings. Therefore, the initial forging temperature is controlled to be 1150-1200°C and the final forging temperature is 830-860°C.

[0070] Specifically, in the above step 4, the dispersion treatment includes: heating the forging blank to a first holding temperature of 960-1020°C for 1-2 hours, and then water cooling to room temperature; then keeping it at a second holding temperature of 620-680°C for 2-4 hours, and air cooling to room temperature.

[0071] Specifically, in the above step 4, the purpose of the first insulation is to make the steel reach the austenitizing temperature, so that the carbides are dissolved and refined. Considering that the first insulation temperature is too high and the insulation time is too long, the structure and grains will be coarsened; the insulation temperature is too low and the insulation time is too short, it is difficult to achieve the effect of carbide dissolution and refinement. Therefore, the first insulation temperature is controlled at 960-1020°C and the insulation time is 1-2h.

[0072] Specifically, in the above step 4, the purpose of the second heat preservation is to obtain a granular pearlite structure with ferrite as the matrix and granular carbides uniformly dispersed. Considering that the second heat preservation temperature is too high or too low, it will exceed the pearlite formation temperature range, and the heat preservation time is too long to cause the structure to be coarse, and the time is too short to achieve the effect of pearlite dispersion distribution, therefore, the second heat preservation temperature is controlled to be 620-680°C, and the heat preservation is 2-4h.

[0073] Specifically, in the above step 5, the role of annealing is to reduce the hardness of steel, improve cutting performance and process performance, eliminate or reduce internal stress to prevent deformation and cracking during processing, and refine the grains to make the chemical composition and structure uniform. The annealing process includes: heating the steel after dispersion treatment to 850±10℃, keeping it warm for 1 to 2 hours; furnace cooling to 650±10℃, keeping it warm for 1 to 2 hours, and then furnace cooling to below 400℃. Granular pearlite is the most ideal annealing structure state, which can ensure the uniformity of the structure and has a lower hardness, which is convenient for subsequent cutting. According to the characteristics of steel structure transformation and phase change, it is necessary to carry out specific austenitization of the steel at 850±10℃. In this temperature range, some undissolved carbides are retained as non-spontaneous nucleation points for the decomposition of supercooled austenite to form pearlite nuclei. Subsequently, the supercooled austenite is decomposed in the temperature range of 650±10℃ to obtain a granular pearlite structure with ferrite as the matrix and granular carbides evenly dispersed. The pearlite transformation is completed and stabilized when cooled to 400℃, and then the steel is taken out of the furnace.

[0074] Specifically, in the above step 6, the quenching treatment includes: keeping the temperature at 950-1050° C. for 0.5-2 h, and cooling the product to room temperature by water or oil after it is taken out of the furnace.

[0075] Specifically, in the above step 6, the cryogenic treatment is to reduce the residual austenite content in the steel after quenching and improve the strength and hardness of the steel. The cryogenic treatment includes: keeping warm at -73°C to -84°C for 0.5 to 2h and air cooling to room temperature.

[0076] Specifically, in the above step 6, high temperature tempering or low temperature tempering treatment can be performed according to the user's requirements for the hardness of the steel.

[0077] Specifically, in the above step 6, the high temperature tempering treatment can be performed at 450-700° C., and the tempering holding time is 1-5 hours.

[0078] Specifically, in the above step 6, the low temperature tempering treatment can be performed at 150 to 280° C., and the tempering holding time is 0.5 to 5 hours.

[0079] Specifically, in the above step 6, the structure of the steel after quenching treatment is martensite and a small amount of undissolved carbides with a size of about 1 μm, with uniform grains and fine grains, for example, a grain size of about level 9.

[0080] Specifically, in the above step 6, the structure of the steel after low temperature tempering treatment is martensite + fine dispersed carbides and carbonitrides, the martensite laths are uniform, no obvious network segregation and strip segregation are observed, the structure is more uniform, the carbides and carbonitrides are less and the size is less than 1 μm, and they are more finely dispersed in the matrix structure. The uniformity of the structure is beneficial to the improvement of various performance properties of the steel.

[0081] Specifically, in the above step 6, the structure of the steel after high temperature tempering treatment is martensite + fine dispersed carbides and carbonitrides, the high temperature tempering precipitates are mostly about 1 μm in size, and the precipitates are finely dispersed in the matrix structure. The uniformity of the structure is beneficial to the improvement of various performance properties of the steel.

[0082] Specifically, in the above step 6, the steel after low temperature tempering treatment can reach a room temperature hardness of ≥56HRC (for example, 56.5-62HRC), and there are hard carbides and carbonitride precipitation phases that can resist wear, which play a dual strengthening role of solid solution strengthening and precipitation strengthening. While having a high hardness, it can also play an effect of enhancing wear resistance.

[0083] Specifically, in the above step 6, the steel after high temperature tempering treatment can have higher impact toughness and tensile strength, for example, impact toughness Ak ≥ 460J (for example 462 ~ 600J), tensile strength ≥ 1040MPa (for example 1048 ~ 1350MPa).

[0084] Specifically, in the above step 6, the steel after high temperature tempering treatment has uniform structure, dispersed carbonitrides and small size, good interface coordination between carbonitrides and martensite matrix, few pitting origins, and a 120h salt spray corrosion test using 5% NaCl solution, with a corrosion rate of 0.012g / m 2 ·h or less, excellent corrosion resistance.

[0085] Compared with the prior art, the high-hardness, high-wear-resistant and corrosion-resistant steel of the present invention obtains martensite and fine dispersed precipitation phases by adding appropriate amounts of CrNi, Mo and N elements under appropriate dispersion treatment and quenching + deep cooling + tempering processes, thereby obtaining higher strength and hardness.

[0086] The high-hardness, high-wear-resistant and corrosion-resistant steel of the present invention obtains good impact toughness and reduces element and tissue segregation through the alloying design of Cr-Ni-Mo-N composite alloying; obtains higher strength and hardness by means of nitrogen element distribution strengthening technology, and thus can obtain good wear resistance; the Mo-Ni composite corrosion resistance treatment of the present invention, and through reasonable element matching, through a dispersion treatment preparation process and an appropriate heat treatment process, obtains more excellent corrosion resistance.

[0087] The high-hardness, high-wear-resistant and corrosion-resistant steel prepared by the composition and method of the present invention has good comprehensive mechanical properties. The steel after low-temperature tempering can reach a room temperature hardness of ≥56HRC. It contains hard carbides and carbonitride precipitation phases that can resist wear, and plays a dual strengthening role of solid solution strengthening and precipitation strengthening. While having a high hardness, it can also enhance the wear resistance. After high-temperature tempering, the steel can have high impact toughness and tensile strength, for example, impact toughness Ak ≥460J, and tensile strength ≥1040MPa. At the same time, it has excellent corrosion resistance, with a corrosion rate of 0.012g / m 2 ·h or less.

[0088] Examples 1-6

[0089] Embodiments 1-6 of the present invention provide a high-hardness, high-wear-resistant and corrosion-resistant steel and a preparation method thereof. The components of the steel in Embodiments 1-4 include, by mass percentage: C: 0.25% to 0.50%, Si: ≤1%, Mn: ≤1%, Cr: 15.0% to 20.0%, Ni: 0.005% to 2.0%, Mo: 0.9% to 3.0%, V: ≤0.20%, N: 0.35% to 0.60%, and the remainder is Fe and unavoidable impurities.

[0090] Specifically, one or more of the following elements may be added to the steel of Examples 5-6, in percentage by mass: W≤0.5%, Cu≤0.5%, Nb≤0.05%, Co≤0.5%, rare earth elements≤0.05%.

[0091] The compositions of the steels of Examples 1-6 are shown in Table 1 below.

[0092] The method for preparing the steel of Examples 1-6 comprises:

[0093] (1) casting molten steel into ingots;

[0094] (2) Heat the ingot to 1160-1200°C, keep it warm for 10-15 hours, and then forge it into and The initial forging temperature is 1150~1200℃, and the final forging temperature is 830~860℃;

[0095] (3) Dispersion treatment of the rod: heating to the first holding temperature of 960-1020°C for 1-2 hours, then water cooling to room temperature; then keeping at the second holding temperature of 620-680°C for 2-4 hours, and air cooling to room temperature;

[0096] (4) Then annealing treatment is carried out: the steel after dispersion treatment is heated to 850±10℃ and kept at this temperature for 1-2h, slowly cooled to 650±10℃ and kept at this temperature for 1-2h, and after being cooled to below 400℃ and taken out of the furnace, it is processed into a sample and subjected to quenching, deep cooling and tempering treatment. The process of quenching, deep cooling and tempering treatment is shown in Table 2.

[0097] Table 1 Chemical composition (%)

[0098]

[0099]

[0100] Table 2 Heat treatment process

[0101]

[0102] After quenching at different temperatures, Example 2, Example 3, Example 5, and Example 6 have finer grain sizes than the comparative steel, and as the quenching temperature increases, the grain coarsening degree of the steel in the example is smaller, and the grain size is about 9, while the grain size of the comparative steel is only about 8. The grain size diagram of Example 2 after quenching is shown in FIG. Figure 1 , Figure 2 As shown, the grain size diagram of the steel of comparative example 1 after quenching is shown in Figure 3 , Figure 4 The grain size grades are shown in Table 3.

[0103] Table 3 Grain size grade at different quenching temperatures

[0104]

[0105] Example 4 and Comparative Example 1 are treated according to the heat treatment process of quenching, deep cooling, low temperature and high temperature tempering. The tempered structure of Example 4 is martensite + carbide and carbonitride, and the tempered structure of Comparative Example 1 is martensite + carbide. The low-temperature tempering and high-temperature tempering structures of the steel of Example 4 have dispersed carbonitrides, dense structures, and fine carbide particles are dispersedly distributed. The carbide particles in the tempered structure of Comparative Example 1 are larger, and there is a phenomenon of large-particle carbide aggregation. The structure of Example 4 is more uniform than that of Comparative Example 1, and the carbides and carbonitrides are finer and dispersed on the matrix structure. The uniform structure is beneficial to various performance properties of the steel. Figure 5 This is the low temperature tempering structure diagram of Example 4. Figure 6 This is the high temperature tempering structure diagram of Example 4, Figure 7 This is the low temperature tempering SEM image of Example 4. Figure 8 This is the high temperature tempering SEM image of Example 4; Fig. 9 This is the low temperature tempering organization diagram of Comparative Example 1, Fig.10 This is the low temperature tempering SEM image of Comparative Example 1. Fig.11 This is the high temperature tempering organization diagram of Comparative Example 1, Fig.12 This is the high temperature tempering SEM image of ratio 1.

[0106] Experiments were conducted according to different heat treatment processes, and the results are shown in Table 4. Different quenching temperatures, cryogenic treatments and tempering temperatures were selected for heat treatment, and Examples 1-6 of the present invention had higher hardness values ​​than Comparative Example 1. The room temperature hardness under some heat treatment processes could reach 60HRC.

[0107] Table 4 Hardness of the embodiment and comparison steel under different heat treatment processes

[0108]

[0109] Experiments were conducted through the heat treatment processes of process 4 and process 5, and the results are shown in Table 5. Examples 1-6 of the present invention have higher impact toughness and tensile strength than Comparative Example 1, and are more excellent in both strength and toughness.

[0110] Table 5 Impact toughness and tensile strength of the example and comparative steels under different heat treatment processes

[0111]

[0112] After the heat treatment of process 6, the corrosion resistance test was carried out, and the corrosion rates of the embodiment and the comparative example are shown in Table 6. The corrosion rate of the embodiment is much lower than that of the comparative example, for example, the corrosion rate is 0.012 g / m 2 ·h or less, excellent corrosion resistance.

[0113] Table 6 Corrosion resistance comparison between the examples and the comparative steels

[0114]

[0115] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing nitrogen-distributed reinforced high-hardness, high-wear-resistant and corrosion-resistant steel, characterized in that: The components of the nitrogen distribution-strengthened high-hardness, high-wear-resistant and corrosion-resistant steel include, by mass percentage: C: 0.25% to 0.50%, Si: ≤1%, Mn: ≤1%, Cr: 15.0% to 20.0%, Ni: 0.005% to 2.0%, Mo: 0.9% to 3.0%, V: ≤0.20%, N: 0.35% to 0.60%, and the balance is Fe and unavoidable impurities; The preparation method comprises: Step 1, smelting and casting to obtain an electrode blank, and subjecting the electrode blank to slow cooling or heat preservation annealing treatment; Step 2, remelting the electrode blank in a pressurized electroslag furnace, casting it into a steel ingot, and subjecting the steel ingot to slow cooling or heat preservation annealing treatment; Step 3, forging the steel ingot to obtain a forging blank; Step 4, dispersing the forging blank; Step 5, annealing the steel after dispersion treatment; Step 6, quenching the annealed steel, followed by deep cooling, and then tempering; In step 4, the dispersion treatment includes: heating the forging blank to a first holding temperature of 960-1020° C. for 1-2 hours, and then water cooling to room temperature; then holding at a second holding temperature of 620-680° C. for 2-4 hours, and air cooling to room temperature; In step 5, the annealing treatment includes: heating the steel after dispersion treatment to 850±10°C, keeping the temperature for 1 to 2 hours; cooling the steel to 650±10°C, keeping the temperature for 1 to 2 hours, and then cooling the steel to below 400°C before taking it out of the furnace; In step 6, the quenching treatment includes: keeping the temperature at 950-1050° C. for 0.5-2 hours, cooling with water or oil to room temperature after being taken out of the furnace; In step 6, the cryogenic treatment includes: keeping warm at -73°C to -84°C for 0.5 to 2 hours, and air cooling to room temperature.

2. The preparation method according to claim 1, characterized in that: In the step 3, the forging includes: fully heating the steel ingot and keeping it warm before forging; the heating temperature is controlled to be 1160-1200° C. and the keeping time is 10-15 hours.

3. The preparation method according to claim 1, characterized in that: In step 3, the initial forging temperature is 1150-1200°C, and the final forging temperature is 830-860°C.

4. A nitrogen distribution strengthened high hardness high wear and corrosion resistant steel, characterized in that: The nitrogen distribution strengthened high hardness high wear and corrosion resistant steel is prepared by the preparation method described in any one of claims 1 to 3.

5. The nitrogen distribution-strengthened high-hardness, high-wear-resistant and corrosion-resistant steel according to claim 4, characterized in that: The components of the nitrogen distribution-strengthened high-hardness, high-wear-resistant and corrosion-resistant steel are further added with one or more of the following elements, in percentage by mass: W≤0.5%, Cu≤0.5%, Nb≤0.05%, Co≤0.5%, and rare earth elements≤0.05%.

6. The nitrogen distribution-strengthened high-hardness, high-wear-resistant and corrosion-resistant steel according to claim 4, characterized in that: The components of the nitrogen distribution-strengthened high-hardness, high-wear-resistant and corrosion-resistant steel include, by mass percentage: C: 0.26% to 0.49%, Si: 0.3% to 0.9%, Mn: 0.25% to 0.9%, Cr: 15.2% to 20.0%, Ni: 0.006% to 2.0%, Mo: 0.95% to 3.0%, V: ≤0.20%, N: 0.35% to 0.60%, and the remainder is Fe and unavoidable impurities.

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