A high-strength and high-corrosion-resistant martensitic stainless steel wire rod and its preparation method

Abstract

The present invention discloses a high-strength and high-corrosion-resistant martensitic stainless steel wire rod and a preparation method thereof. The chemical composition of the wire rod is as follows by mass: C: 0.08% to 0.18%, Si: 0.10% to 0.70%, Mn: 0.10% to 0.70%, P≤0.040%, S≤0.010%, Cr: 12.50% to 14.00%, Mo: 2.00% to 2.50%, Ni: 1.00% to 2.00%, N: 0.060% to 0.120%, Nb: 0.05% to 0.20%, and the pitting corrosion resistance equivalent is controlled to be ≥21. The preparation method of the wire rod comprises the steps of preparing a square billet, heating the square billet, hot rolling the wire rod, annealing heat treatment of the wire rod, and quenching and tempering heat treatment of the wire rod. The high strength and high corrosion resistance martensitic stainless steel wire rod of the present invention has a Vickers hardness (HV10) of ≥400 and a tensile strength R m ≥1100MPa, yield strength R p0.2 ≥750MPa, and there is no rust under 72h neutral salt spray test conditions. Therefore, the high-strength and high-corrosion-resistant martensitic stainless steel wire rod of the present invention has high strength performance and high corrosion resistance, and meets the processing and use requirements of self-tapping bolts, high-strength pins, high-strength chains and other spare parts with high requirements on material strength and corrosion resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of stainless steel wire production, and in particular relates to a high-strength and high-corrosion-resistant martensitic stainless steel wire rod and a preparation method thereof. Background Art

[0002] Low-carbon martensitic stainless steels such as 12Cr13 and 20Cr13 are a type of stainless steel whose strength and hardness can be increased through quenching and tempering heat treatment. Wire rods made from these stainless steels are widely used in the production of standard parts requiring a certain level of strength and hardness, but with low corrosion resistance. However, due to their low Cr and N content, the performance of these wire rods cannot meet the requirements of various standard parts such as high-strength pins, highly corrosion-resistant self-tapping screws, and high-strength chains, which require high material properties.

[0003] The Chinese invention patent application with application number 201210387750.X discloses "high-toughness, wear-resistant and corrosion-resistant martensitic stainless steel and its manufacturing method." The chemical composition of this stainless steel contains 0.4% to 1.0% molybdenum by mass. Although the lower Mo content can reduce the production cost of the material, it also reduces the corrosion resistance of the material. In addition, the patent application does not provide a specific description of the evaluation and testing methods for the corrosion resistance of the material involved and the technical indicators that can be achieved.

[0004] Therefore, developing a martensitic stainless steel wire rod with high strength and good corrosion resistance has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a high-strength and high-corrosion-resistant martensitic stainless steel wire rod and a preparation method thereof.

[0006] In one aspect of the present invention, the chemical composition of the provided high-strength and high-corrosion-resistant martensitic stainless steel wire rod is as follows by mass percentage: C: 0.08%~0.18%, Si: 0.10%~0.70%, Mn: 0.10%~0.70%, P≤0.040%, S≤0.010%, Cr: 12.50%~14.00%, Mo: 2.00%~2.50%, Ni: 1.00%~2.00%, N: 0.060%~0.120%, Nb: 0.05%~0.20%, and the remainder is Fe and unavoidable impurities, and the pitting resistance equivalent PRE of the high-strength and high-corrosion-resistant martensitic stainless steel wire rod is controlled to be PRE=%Cr+3.3×%Mo+16×%N≥21.

[0007] Preferably, the chemical composition of the high-strength and high-corrosion-resistant martensitic stainless steel wire rod is as follows by mass percentage: C: 0.08% to 0.16%, Si: 0.20% to 0.60%, Mn: 0.20% to 0.60%, P≤0.040%, S≤0.005%, Cr: 13.00% to 14.00%, Mo: 2.10% to 2.50%, Ni: 1.20% to 1.50%, N: 0.070% to 0.110%, Nb: 0.05% to 0.15%, and the remainder is Fe and unavoidable impurities.

[0008] As a specific implementation manner, the diameter specification range of the high-strength and high-corrosion-resistant martensitic stainless steel wire rod is Φ5.5mm to Φ25mm.

[0009] In another aspect of the present invention, a method for preparing a high-strength and high-corrosion-resistant martensitic stainless steel wire rod is provided, comprising the following steps:

[0010] The billet is prepared by a process flow of electric arc furnace or medium frequency induction furnace → argon oxygen refining furnace → ladle refining furnace → mold casting steel ingot → electroslag smelting → electroslag ingot blanking; or the billet is prepared by a process flow of converter → vacuum degassing furnace → ladle refining furnace → mold casting steel ingot → electroslag smelting → electroslag ingot blanking;

[0011] Billet heating: Place the billet in a walking beam furnace for heating. The temperature of the heating section is controlled at 1000℃~1220℃, and the heating time of the heating section is controlled at 60min~120min. The temperature of the soaking section is controlled at 1200℃~1260℃, and the holding time of the soaking section is controlled at 40min~80min.

[0012] Hot rolling of wire rod: high-pressure water is used to remove phosphorus from the surface of the heated square billet, which is then opened into round bloom on a blooming mill at a temperature of 950°C to 1150°C. The bloom is then heated by electromagnetic induction and hot-rolled into wire rod on a rolling mill at a temperature of 900°C to 1100°C.

[0013] Annealing heat treatment of wire rod: The hot-rolled wire rod is subjected to two annealing heat treatments, specifically including: the first annealing, the wire rod is heated with the furnace to a temperature range of 880℃~950℃ and kept warm for 2h~10h, after which the wire rod is cooled to 500℃ at a cooling rate of 10℃ / h~20℃ / h, then removed from the furnace and air-cooled to room temperature; the second annealing, the wire rod is heated with the furnace to a temperature range of 650℃~750℃ and kept warm for 2h~10h, after which the wire rod is cooled to 500℃ at a cooling rate of 10℃ / h~20℃ / h, then removed from the furnace and air-cooled to room temperature;

[0014] Tempering heat treatment of wire rod: Tempering heat treatment includes quenching treatment and tempering treatment, wherein the quenching treatment includes heating the wire rod to 1140℃~1160℃ and then keeping it warm, the quenching holding time (unit: min) = (0.8~1.0min / mm) × wire rod diameter (unit: mm), and oil cooling to room temperature after the insulation is completed; the tempering treatment includes heating the quenched wire rod to 210℃~230℃ and then keeping it warm, the tempering holding time (unit: min) = (4~6min / mm) × wire rod diameter (unit: mm), and air cooling to room temperature after the insulation is completed.

[0015] Preferably, in the above-mentioned method for preparing high-strength and high-corrosion-resistant martensitic stainless steel wire rod, in the heating step of the square billet, the temperature of the heating section is controlled to be 1050℃~1200℃, and the heating time of the heating section is controlled to be 60min~90min; the temperature of the soaking section is controlled to be 1220℃~1240℃, and the holding time of the soaking section is controlled to be 40min~60min.

[0016] Preferably, in the preparation method of the above-mentioned high-strength and high-corrosion-resistant martensitic stainless steel wire rod, in the annealing heat treatment step of the wire rod, for the first annealing, the wire rod is heated to 910°C~930°C with the furnace and kept warm for 3h~5h; for the second annealing, the wire rod is heated to 680°C~700°C with the furnace and kept warm for 3h~5h.

[0017] Preferably, in the method for preparing the high-strength and high-corrosion-resistant martensitic stainless steel wire rod, in the step of preparing the square billet, the cross-sectional dimensions of the square billet are: length 140 mm to 220 mm × width 140 mm to 220 mm.

[0018] The high-strength and high-corrosion-resistant martensitic stainless steel wire rod and the preparation method thereof of the present invention have the following advantages and beneficial effects:

[0019] The high strength and high corrosion resistance martensitic stainless steel wire rod of the present invention has a Vickers hardness (HV10) of ≥400 and a tensile strength R m ≥1100MPa, yield strength R p0.2 ≥750MPa, and there is no rust under 72h neutral salt spray test conditions. It can be seen that the high-strength and high-corrosion-resistant martensitic stainless steel wire rod of the present invention has high strength performance and high corrosion resistance, and meets the processing and use requirements of self-tapping bolts, high-strength pins, high-strength chains and other spare parts with high requirements on material strength and corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 The microstructure of the high-strength and high-corrosion-resistant martensitic stainless steel wire rod of the present invention after annealing heat treatment.

[0022] Figure 2 This is the microstructure morphology of the high-strength and high-corrosion-resistant martensitic stainless steel wire rod of the present invention after quenching and tempering (quenching + tempering) heat treatment. DETAILED DESCRIPTION

[0023] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] Martensitic stainless steel contains a variety of alloying elements, and the functions of these elements can be divided into two categories: one is the elements that can improve the pitting corrosion resistance, such as adding Cr, Mo, N and other elements to improve the pitting corrosion resistance of steel, and the added weight must meet the pitting corrosion resistance equivalent requirements in terms of mass percentage; the other is the elements that improve the strength of steel, such as adding Ni to improve the hardenability and hardenability of steel, and adding C to improve the strength and hardness of steel.

[0025] Based on the above mechanism, the present invention takes into account the range of alloying element content by mass in the material and the design objectives of economic efficiency, high strength, high corrosion resistance and other performance characteristics. After multiple production and application verifications, a high-strength and high-corrosion-resistant martensitic stainless steel wire rod has been developed. Specifically, the chemical composition of the high-strength and high-corrosion-resistant martensitic stainless steel wire rod of the present invention is as follows by mass percentage: C: 0.08% to 0.18%, Si: 0.10% to 0.70%, Mn: 0.10% to 0.70%, P ≤ 0.040%, S ≤ 0.010%, Cr: 12.50% to 14.00%, Mo: 2.00% to 2.50%, Ni: 1.00% to 2.00%, N: 0.060% to 0.120%, Nb: 0.05% to 0.20%, and the balance is Fe and unavoidable impurities.

[0026] Furthermore, the pitting corrosion equivalent PRE of the high-strength and high-corrosion-resistant martensitic stainless steel wire rod of the present invention is controlled to be PRE=%Cr+3.3×%Mo+16×%N≥21.

[0027] As a specific embodiment, the diameter specification range of the high-strength and high-corrosion-resistant martensitic stainless steel wire rod of the present invention is Φ5.5mm to Φ25mm.

[0028] The following details the effects of the various components in the high-strength and high-corrosion-resistant martensitic stainless steel wire rod of the present invention and the preferred ranges of their contents:

[0029] C: A strong austenite-forming element, 30 times more powerful than Ni. As the carbon content in steel increases, the strength and hardness of the steel after quenching increase, while its plasticity decreases. Carbon is a detrimental factor to the corrosion resistance of stainless steel. Therefore, the carbon content in the high-strength, high-corrosion-resistant martensitic stainless steel wire rod of the present invention is controlled to be between 0.08% and 0.18%, and preferably, between 0.08% and 0.16%.

[0030] Si: A ferrite-forming element, it improves stainless steel's corrosion resistance, intergranular corrosion resistance, and pitting corrosion resistance in oxidizing media. However, excessive silicon content can reduce the steel's mechanical properties. Therefore, the Si content in the high-strength, high-corrosion-resistant martensitic stainless steel wire rod of the present invention is controlled to be between 0.10% and 0.70%, and preferably, between 0.20% and 0.60%.

[0031] Mn: An element that expands the austenite region and stabilizes the austenite structure. Its austenite-forming ability is approximately half that of Ni, but it has little effect on the corrosion resistance of stainless steel. Therefore, the Mn content in the high-strength, high-corrosion-resistant martensitic stainless steel wire rod of the present invention is controlled to be 0.10% to 0.70%, and preferably, the Mn content is controlled to be 0.20% to 0.60%.

[0032] P: is considered a harmful element in steel and the lower its content, the better. Therefore, the P content in the high-strength and high-corrosion-resistant martensitic stainless steel wire rod of the present invention is controlled to be ≤0.040%.

[0033] S: An element that reduces the corrosion resistance of stainless steel. MnS formed by S and Mn in stainless steel is easily soluble in the pickling chloride solution, reducing the corrosion resistance of the stainless steel. Therefore, the S content in the high-strength, high-corrosion-resistant martensitic stainless steel wire rod of the present invention is controlled to ≤ 0.010%, and preferably, the S content is controlled to ≤ 0.005%.

[0034] Cr: A ferrite-forming element, it forms a dense, stable Cr2O3 protective film on the stainless steel surface, preventing the medium from further penetrating and corroding the metal matrix. Therefore, the Cr content in the high-strength, high-corrosion-resistant martensitic stainless steel wire rod of the present invention is controlled to be 12.50% to 14.00%, and preferably, the Cr content is controlled to be 13.00% to 14.00%.

[0035] Mo: A ferrite-forming element, it makes the passive film on the surface of stainless steel denser and stronger, thereby effectively improving the corrosion resistance of stainless steel. Therefore, the Mo content in the high-strength, high-corrosion-resistant martensitic stainless steel wire rod of the present invention is controlled to be 2.00% to 2.50%, and preferably, the Mo content is controlled to be 2.10% to 2.50%.

[0036] Nickel (Ni): An austenite-forming element, Ni can expand the austenite phase and promote martensitic transformation, thereby improving the hardenability and corrosion resistance of the steel. Therefore, the Ni content in the high-strength, high-corrosion-resistant martensitic stainless steel wire rod of the present invention is controlled to be 1.00% to 2.00%, and preferably, the Ni content is controlled to be 1.20% to 1.50%.

[0037] Nitrogen: A strong austenite-forming element, its ability is comparable to that of carbon. As a solid solution strengthening element, nitrogen improves the strength and corrosion resistance of steel. Therefore, the nitrogen content in the high-strength, high-corrosion-resistant martensitic stainless steel wire rod of the present invention is controlled to be 0.060% to 0.120%, and preferably, the nitrogen content is controlled to be 0.070% to 0.110%.

[0038] Nb: A ferrite-forming element, it converts chromium carbon and nitrides in the steel into niobium carbon and nitrides, thereby refining the grain size. Therefore, the Nb content in the high-strength, high-corrosion-resistant martensitic stainless steel wire rod of the present invention is controlled to be 0.05% to 0.20%, and preferably, the Nb content is controlled to be 0.05% to 0.15%.

[0039] On the other hand, the method for preparing the high-strength and high-corrosion-resistant martensitic stainless steel wire rod of the present invention comprises the following steps:

[0040] The square billet is prepared through the process of electric arc furnace (EAF) or medium frequency induction furnace → argon oxygen refining furnace (AOD) → ladle refining furnace (LF furnace) → mold casting ingot → electroslag smelting → electroslag ingot blooming; or, the square billet is prepared through the process of converter (K-OBM-S) → vacuum degassing furnace (VD) → ladle refining furnace (LF furnace) → mold casting ingot → electroslag smelting → electroslag ingot blooming.

[0041] Heating of the billet: Place the billet in a walking beam heating furnace for heating. The temperature of the heating section is controlled at 1000℃~1220℃, and the heating time of the heating section is controlled at 60min~120min; the temperature of the soaking section is controlled at 1200℃~1260℃, and the holding time of the soaking section is controlled at 40min~80min.

[0042] Hot rolling of wire rod: Use high-pressure water to remove phosphorus from the surface of the heated square billet, and then open the billet into a round bloom on the blooming rolling mill. The blooming temperature is controlled at 950℃~1150℃. Then the round bloom is heated by electromagnetic induction and then hot-rolled into wire rod through the rolling mill. The hot rolling temperature of the wire rod is controlled at 900℃~1100℃.

[0043] Annealing heat treatment of wire rod: In order to make the wire rod have good cold working performance, the hot rolled wire rod is subjected to two annealing heat treatments, specifically including: the first annealing, the wire rod is heated with the furnace to a temperature range of 880℃~950℃ and kept warm, the holding time is controlled to be 2h~10h, after the end of the holding, the wire rod is cooled to 500℃ at a cooling rate of 10℃ / h~20℃ / h, and then it is taken out of the furnace and air-cooled to room temperature; the second annealing, the wire rod is heated with the furnace to a temperature range of 650℃~750℃ and kept warm, the holding time is controlled to be 2h~10h, after the end of the holding, the wire rod is cooled to 500℃ at a cooling rate of 10℃ / h~20℃ / h, and then it is taken out of the furnace and air-cooled to room temperature. The microstructure morphology of the wire rod after annealing heat treatment can be found in Figure 1 .

[0044] Wire rod quenching and tempering heat treatment: quenching and tempering heat treatment includes quenching and tempering treatment, wherein quenching treatment includes heating the wire rod to 1140℃~1160℃ and then holding the temperature. The quenching and holding time (unit: min) = (0.8~1.0min / mm) × wire rod diameter (unit: mm). After holding the temperature, oil cooling is performed to room temperature. Tempering treatment includes heating the quenched wire rod to 210℃~230℃ and then holding the temperature. The tempering and holding time (unit: min) = (4~6min / mm) × wire rod diameter (unit: mm). After holding the temperature, air cooling is performed to room temperature. The microstructure morphology of the wire rod after quenching and tempering (quenching + tempering) heat treatment can be found in Figure 2 .

[0045] Preferably, in the preparation method of high-strength and high-corrosion-resistant martensitic stainless steel wire rod of the present invention, in the heating step of the square billet, the temperature of the heating section is controlled to be 1050℃~1200℃, and the heating time of the heating section is controlled to be 60min~90min; the temperature of the soaking section is controlled to be 1220℃~1240℃, and the holding time of the soaking section is controlled to be 40min~60min.

[0046] Preferably, in the preparation method of high-strength and high-corrosion-resistant martensitic stainless steel wire rod of the present invention, in the annealing heat treatment step of the wire rod, for the first annealing, the wire rod is heated with the furnace to 910°C~930°C and kept warm for 3h~5h; for the second annealing, the wire rod is heated with the furnace to 680°C~700°C and kept warm for 3h~5h.

[0047] As a specific embodiment, in the method for preparing high-strength and high-corrosion-resistant martensitic stainless steel wire rod of the present invention, in the step of preparing square billets, the cross-sectional dimensions of the square billets are: length 140 mm to 220 mm × width 140 mm to 220 mm.

[0048] As a specific embodiment, in the method for preparing high-strength and high-corrosion-resistant martensitic stainless steel wire rod of the present invention, in the hot rolling step of the wire rod, the diameter specification range of the hot-rolled wire rod is Φ5.5mm to Φ25mm.

[0049] The performance test results of the wire rod prepared by the preparation method of the high-strength and high-corrosion-resistant martensitic stainless steel wire rod of the present invention are as follows: Vickers hardness (HV10) ≥ 400 (applicable standard GB / T 4340.4-2022 "Metallic Materials Vickers Hardness Test Part 4: Hardness Value Table"); tensile strength R m ≥1100MPa, yield strength R p0.2 ≥750MPa (applicable standard: GB / T228.1-2021 "Tensile test of metallic materials - Part 1: Test method at room temperature"); no rust after 72h of neutral salt spray test conditions (applicable standard: GB / T 10125-2021 "Salt spray test for corrosion in artificial atmosphere").

[0050] It can be seen that the high-strength and high-corrosion-resistant martensitic stainless steel wire rod of the present invention has high strength performance and high corrosion resistance, which meets the processing and use requirements of self-tapping bolts, high-strength pins, high-strength chains and other spare parts with high requirements on material strength and corrosion resistance.

[0051] The following describes in detail the method for preparing the high-strength and high-corrosion-resistant martensitic stainless steel wire rod of the present invention in conjunction with specific embodiments.

[0052] Example 1

[0053] Example 1 of the present invention is applied to produce a high-strength and high-corrosion-resistant martensitic stainless steel wire rod with a diameter of Φ5.5 mm, comprising the following steps:

[0054] The square billet is prepared by an electric arc furnace (EAF) or a medium frequency induction furnace → an argon oxygen refining furnace (AOD) → a ladle refining furnace (LF furnace) → a mold-cast steel ingot → electroslag smelting → electroslag ingot blooming to prepare a square billet with a cross-sectional side length of 220 mm × 220 mm. The chemical composition of the billet is as follows by mass percentage: C: 0.084%, S: 0.31%, Mn: 0.41%, P: 0.028%, S: 0.003%, Cr: 13.75%, Mo: 2.14%, Ni: 1.28%, N: 0.082%, Nb: 0.06%, and the balance is Fe and unavoidable impurities. The pitting corrosion equivalent PRE of the billet is %Cr+3.3×%Mo+16×%N=22.124.

[0055] Heating of the billet: Place the billet in a walking beam heating furnace for heating. The temperature of the heating section is controlled at 1050℃~1220℃, and the heating time of the heating section is controlled at 90min; the temperature of the soaking section is controlled at 1220℃~1240℃, and the holding time of the soaking section is controlled at 50min.

[0056] Hot rolling of wire rod: high-pressure water is used to remove phosphorus from the surface of the heated square billet, and the billet is opened into Φ85mm round bloom on the blooming rolling mill. The blooming temperature is controlled at 1020℃~1135℃, and then the round bloom is subjected to electromagnetic induction heating, and then hot-rolled into wire rod with a diameter of Φ5.5mm on the rolling mill.

[0057] Annealing heat treatment of wire rod: The hot-rolled wire rod is subjected to two annealing heat treatments: For the first annealing, the wire rod is heated to 910℃~930℃ with the furnace and kept warm for 3 hours. After the insulation, the wire rod is cooled to 500℃ at a cooling rate of 10℃ / h~20℃ / h, and then taken out of the furnace and air-cooled to room temperature; For the second annealing, the wire rod is heated to 680℃~700℃ with the furnace and kept warm for 5 hours. After the insulation, the wire rod is cooled to 500℃ at a cooling rate of 10℃ / h~20℃ / h, and then taken out of the furnace and air-cooled to room temperature.

[0058] Tempering heat treatment of wire rod: Tempering heat treatment includes quenching treatment and tempering treatment, among which, quenching treatment includes heating the wire rod to 1140℃~1160℃, keeping it warm for 5 minutes and then oil cooling it to room temperature; tempering treatment includes heating the quenched wire rod to 210℃~230℃, keeping it warm for 30 minutes and then air cooling it to room temperature.

[0059] The performance test of the Φ5.5mm wire rod prepared by Example 1 showed that the Vickers hardness (HV10) was 441 and the tensile strength R m The yield strength R is 1233MPa. p0.2 The hardness is 819MPa, and there is no rust under the neutral salt spray test conditions for 72 hours.

[0060] Example 2

[0061] Example 2 of the present invention is applied to the production of high-strength and high-corrosion-resistant martensitic stainless steel wire rod with a diameter of Φ6.5 mm, comprising the following steps:

[0062] The square billet is prepared by a process flow of converter (K-OBM-S) → vacuum degassing furnace (VD) → ladle refining furnace (LF furnace) → mold casting ingot → electroslag smelting → electroslag ingot blooming to prepare a square billet with a cross-sectional side length of 220 mm × 220 mm. The chemical composition of the billet is as follows by mass percentage: C: 0.14%, Si: 0.34%, Mn: 0.36%, P: 0.031%, S: 0.001%, Cr: 13.83%, Mo: 2.12%, Ni: 1.27%, N: 0.104%, Nb: 0.12%, and the balance is Fe and unavoidable impurities. Among them, the pitting corrosion resistance equivalent PRE of the billet is %Cr+3.3×%Mo+16×%N=22.49.

[0063] Heating of the billet: The billet is placed in a walking beam heating furnace for heating. The temperature of the heating section is controlled at 1050℃~1220℃, and the heating time of the heating section is controlled at 85min; the temperature of the soaking section is controlled at 1220℃~1240℃, and the holding time of the soaking section is controlled at 60min.

[0064] Hot rolling of wire rod: high-pressure water is used to remove phosphorus from the surface of the heated square billet, and the billet is opened into Φ85mm round bloom on the blooming rolling mill. The blooming temperature is controlled at 1000℃~1140℃, and then the round bloom is subjected to electromagnetic induction heating, and then hot-rolled into wire rod with a diameter of Φ6.5mm on the rolling mill.

[0065] Annealing heat treatment of wire rod: The hot-rolled wire rod is subjected to two annealing heat treatments: For the first annealing, the wire rod is heated to 910℃~930℃ with the furnace and kept warm for 3 hours. After the insulation, the wire rod is cooled to 500℃ at a cooling rate of 10℃ / h~20℃ / h, and then taken out of the furnace and air-cooled to room temperature; For the second annealing, the wire rod is heated to 680℃~700℃ with the furnace and kept warm for 5 hours. After the insulation, the wire rod is cooled to 500℃ at a cooling rate of 10℃ / h~20℃ / h, and then taken out of the furnace and air-cooled to room temperature.

[0066] Tempering heat treatment of wire rod: Tempering heat treatment includes quenching treatment and tempering treatment, among which, quenching treatment includes heating the wire rod to 1140℃~1160℃, keeping it warm for 6 minutes and then oil cooling it to room temperature; tempering treatment includes heating the quenched wire rod to 210℃~230℃, keeping it warm for 35 minutes and then air cooling it to room temperature.

[0067] The performance test of the Φ6.5mm wire rod prepared by Example 2 showed that the Vickers hardness (HV10) was 554 and the tensile strength R m The yield strength R is 1719MPa.p0.2 The hardness is 924MPa, and there is no rust under the neutral salt spray test conditions for 72h.

[0068] In summary, compared with the prior art, the high-strength and high-corrosion-resistant martensitic stainless steel wire rod and the preparation method thereof of the present invention have the following advantages and beneficial effects:

[0069] The high strength and high corrosion resistance martensitic stainless steel wire rod of the present invention has a Vickers hardness (HV10) of ≥400 and a tensile strength R m ≥1100MPa, yield strength R p0.2 ≥750MPa, and there is no rust under 72h neutral salt spray test conditions. It can be seen that the high-strength and high-corrosion-resistant martensitic stainless steel wire rod of the present invention has high strength performance and high corrosion resistance, and meets the processing and use requirements of self-tapping bolts, high-strength pins, high-strength chains and other spare parts with high requirements on material strength and corrosion resistance.

[0070] It should be noted that, in this article, the term "comprise" or any other variation thereof is intended to cover non-exclusive inclusion, so that an article or device that includes a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements that are inherent to such article or device.

[0071] It should also be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the present invention.

Claims

1. A method for preparing a high-strength and high-corrosion-resistant martensitic stainless steel wire rod, wherein the chemical composition of the high-strength and high-corrosion-resistant martensitic stainless steel wire rod is as follows by mass percentage: C: 0.08% to 0.18%, Si: 0.10% to 0.70%, Mn: 0.10% to 0.70%, P≤0.040%, S≤0.010%, Cr: 12.50% to 14.00%, Mo: 2.00% to 2.50%, Ni: 1.00% to 2.00%, N: 0.060% to 0.120%, Nb: 0.05% to 0.20%, and the balance is Fe and unavoidable impurities, and the pitting resistance equivalent (PRE) of the high-strength and high-corrosion-resistant martensitic stainless steel wire rod is controlled to be PRE=%Cr+3.3×%Mo+16×%N≥21; The method for preparing the high-strength and high-corrosion-resistant martensitic stainless steel wire rod comprises the following steps: The billet is prepared by a process flow of electric arc furnace or medium frequency induction furnace → argon oxygen refining furnace → ladle refining furnace → mold casting steel ingot → electroslag smelting → electroslag ingot blanking; or the billet is prepared by a process flow of converter → vacuum degassing furnace → ladle refining furnace → mold casting steel ingot → electroslag smelting → electroslag ingot blanking; Billet heating: Place the billet in a walking beam furnace for heating. The temperature of the heating section is controlled at 1000℃~1220℃, and the heating time of the heating section is controlled at 60min~120min. The temperature of the soaking section is controlled at 1200℃~1260℃, and the holding time of the soaking section is controlled at 40min~80min. Hot rolling of wire rod: high-pressure water is used to remove phosphorus from the surface of the heated square billet, which is then opened into round bloom on a blooming mill at a temperature of 950°C to 1150°C. The bloom is then heated by electromagnetic induction and hot-rolled into wire rod on a rolling mill at a temperature of 900°C to 1100°C. Annealing heat treatment of wire rod: The hot-rolled wire rod is subjected to two annealing heat treatments, specifically including: For the first annealing, the wire rod is heated with the furnace to a temperature range of 880°C to 950°C and kept warm for 2h to 10h. After the end of the heat preservation, the wire rod is cooled to 500°C at a cooling rate of 10°C / h to 20°C / h, and then taken out of the furnace and air-cooled to room temperature. For the second annealing, the wire rod is heated with the furnace to a temperature range of 650°C to 750°C and kept warm for 2h to 10h. After the end of the heat preservation, the wire rod is cooled to 500°C at a cooling rate of 10°C / h to 20°C / h, and then taken out of the furnace and air-cooled to room temperature. Wire rod quenching and tempering heat treatment: quenching and tempering heat treatment includes quenching and tempering treatment, wherein the quenching treatment includes heating the wire rod to 1140-1160°C and then holding the temperature. The quenching and holding time is (0.8-1.0 min / mm) × wire rod diameter. After the holding period, the wire rod is oil-cooled to room temperature. The tempering treatment includes heating the quenched wire rod to 210-230°C and then holding the temperature. The tempering and holding time is (4-6 min / mm) × wire rod diameter. After the holding period, the wire rod is air-cooled to room temperature. The units of the quenching and holding time and the tempering and holding time are min, and the unit of the wire rod diameter is mm. The diameter specification range of the high-strength and high-corrosion-resistant martensitic stainless steel wire rod is Φ5.5mm~Φ25mm. The HV10 Vickers hardness of the high-strength and high-corrosion-resistant martensitic stainless steel wire rod is above 441, the tensile strength Rm is above 1233MPa, the yield strength Rp0.2 is above 819MPa, and there is no rust under neutral salt spray test conditions for 72h.

2. The method for preparing high-strength and high-corrosion-resistant martensitic stainless steel wire rod according to claim 1, characterized in that: In the heating step of the square billet, the temperature of the heating section is controlled at 1050℃~1200℃, and the heating time of the heating section is controlled at 60min~90min; the temperature of the soaking section is controlled at 1220℃~1240℃, and the holding time of the soaking section is controlled at 40min~60min.

3. The method for preparing high-strength and high-corrosion-resistant martensitic stainless steel wire rod according to claim 1, characterized in that: In the annealing heat treatment step of the wire rod, for the first annealing, the wire rod is heated to 910°C~930°C with the furnace and kept warm for 3h~5h; for the second annealing, the wire rod is heated to 680°C~700°C with the furnace and kept warm for 3h~5h.

4. The method for preparing high-strength and high-corrosion-resistant martensitic stainless steel wire rod according to claim 1, wherein: In the step of preparing the billet, the cross-sectional dimensions of the billet are: length 140 mm to 220 mm×width 140 mm to 220 mm.

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