CN105839022B

CN105839022B - High-hardness non-magnetic nickel-free stainless steel and manufacturing method thereof

Info

Publication number: CN105839022B
Application number: CN201610196107.7A
Authority: CN
Inventors: 张伟; 张鑫; 杜伟; 吴狄峰
Original assignee: Baosteel Desheng Stainless Steel Co ltd
Current assignee: Baosteel Desheng Stainless Steel Co., Ltd.
Priority date: 2016-03-31
Filing date: 2016-03-31
Publication date: 2021-04-09
Anticipated expiration: 2036-03-31
Also published as: CN105839022A

Abstract

A high-hardness non-magnetic nickel-free stainless steel and a manufacturing method thereof are disclosed, wherein the steel comprises the following chemical components in percentage by weight: c: 0.15 to 0.20%, Si: 0.2-0.8%, Mn: 17.0-19.0%, Cr: 13.5-14.5%, N: 0.25-0.30%, Cu: 0.5-0.8%, B: 0.0015-0.0040% and the balance of Fe and inevitable impurities; and the above elements simultaneously need to satisfy the following relations: c + N is more than or equal to 0.43 percent, Cr + Mo +1.5Si)/(30N +30C +0.25Cu +0.5Mn is more than or equal to 1.20 percent and M is more than or equal to 1.00_d30/50The temperature is less than or equal to-100 ℃. The steel is in a full austenite mode (no delta phase is formed) in the solidification process, the hardness at room temperature reaches HV 425-497, the yield strength is 1100-1350 MPa, the steel is ensured to be nonmagnetic after room temperature deformation hardening reaches high strength, the steel does not contain nickel, demagnetization heat treatment after deformation is not needed, the cost is obviously reduced, and the steel can be widely applied to industries requiring high hardness, wear resistance and no magnetism, such as textiles, electronics, instruments and meters and the like.

Description

High-hardness non-magnetic nickel-free stainless steel and manufacturing method thereof

Technical Field

The invention relates to nickel-free stainless steel and a manufacturing method thereof, in particular to high-hardness non-magnetic nickel-free stainless steel and a manufacturing method thereof.

Background

The hard stainless steel is obtained by subjecting a stainless steel plate or a steel strip to temper rolling (deformation hardening), giving the steel strip a certain cold rolling reduction, and performing no annealing treatment after cold working. The hard stainless steel has higher strength and hardness than the same material after solution treatment (or annealing treatment), so the material is more wear-resistant and has longer service life. The commonly used hard stainless steels are mainly S30400(304) and S30100(301) in 300 series austenitic stainless steels.

Hard stainless steel is commonly used in textile, electronics, instruments and meters and other industries. Taking the textile industry as an example, one process is to utilize a needle detector or a magnetic instrument for detection after finishing garment processing, and if magnetic conductivity is detected, broken textile needles exist in the garment and cannot flow into the next process. When the zipper, the button or the label of the clothing is made of stainless steel, the requirement of non-magnetism (non-magnetic) is required to be met, and the work of the needle detector cannot be interfered. These fields of technology also require high hardness to solve the problems of wear and deformation.

Another problem is that the conventional austenitic stainless steel can meet the requirement of no magnetism under the condition of no deformation, but in the process of processing into buttons, zippers and labels, the processing or deformation process can cause the material to be changed from non-magnetism into magnetism, so that the application can not be met. For example, 304 is nonmagnetic, but when bent or formed, changes from nonmagnetic to magnetic conductive. The conventional process is a degaussing heat treatment, but the degaussing heat treatment causes deformation of the workpiece and increases the cost.

The standard components according to ASTM a240 standard, 304 are: less than or equal to 0.08 percent of C, less than or equal to 0.75 percent of Si, less than or equal to 2.0 percent of Mn, Cr: 18.0-20.0%, Ni: 8.0 to 10.5%, and generally 304 typically contains C0.06%, Si 0.4%, Mn 1.0%, Cr 18%, and Ni 8%. To achieve higher hardness, 304 may be cold work hardened. As shown in FIG. 1, when cold-worked 304 to 30%, the hardness HV increased from HV 179 in the annealed state to HV 376, and the hardness further increased as the amount of deformation increased. However, while the hardness increases, 304 gradually changes from nonmagnetic to magnetically permeable material, i.e., the magnetometer can detect the gradually increasing magnetic phase content.

The process of changing non-magnetic into magnetic property is not only generated in the process of cold working, rolling and hardening to improve the hardness, but also occurs in the process of processing the stainless steel into the required parts, parts or shapes by an end user, and the process is unavoidable, and the magnetic property generated in the process cannot be eliminated by adopting other processes in the subsequent process (the heat treatment can partially eliminate the cold working magnetic phase, but has high cost and easily causes the deformation of the parts). Therefore, the application of 304 or the hard state 304 in the non-magnetic field is limited to the occasions with low requirement on magnetism, and the application of 304 in the field requiring weak magnetism or completely non-magnetic cannot be met by 304.

304 also has a problem in that the price is high, and 8% Ni accounts for more than 50% of the cost of 304 stainless steel. Especially for the industries of spinning and the like sensitive to cost, the high hardness, complete non-magnetic or weak magnetic conduction after processing and forming and low cost are required, and the application of 304 is limited.

304, et al, are in the delta ferrite + austenite solidification mode, and results of studies by j.c. ma, published in Materials Science and Engineering a Volume 444, Issues 1-2, 25January2007, Pages 64-68, show the presence and retention of delta ferrite during the 304 solidification process. The reason why the austenitic stainless steel 304 has magnetism or permeability is that: (1) a magnetic delta phase (ferrite phase) generated during solidification or hot working; (2) a magnetic martensite phase appears after cold working. The main approach to suppressing the appearance of the magnetic phase is to enlarge the austenite phase region during solidification and to improve the stability of the austenite phase during cold working. The conventional approach is to increase the nickel content and thus create a new stainless steel designation S30500(305), with standard components: less than or equal to 0.12 percent of C, less than or equal to 0.75 percent of Si, less than or equal to 2.0 percent of Mn, 17.0 to 19.0 percent of Cr and 10.5 to 13.5 percent of Ni. Typical components commonly used are: 0.06% of C, 0.4% of Si, 1.0% of Mn, 18% of Cr and 10.5% of Ni. After the nickel content is increased, the martensite phase content after 305 cold deformation is far lower than that of 304 stainless steel under the same pressure, so that the application requirement under the low-magnetism condition can be met. However, the cost of 305 stainless steel is greatly increased because the nickel content is as high as 10.5%. Every 1% of nickel in the stainless steel is added, which means that the raw material cost is increased by 10-15%. On the other hand, when the cold working deformation is accumulated to a certain degree, the magnetic property is generated, and the high-level nonmagnetic requirement cannot be satisfied.

Analysis of the austenite to strain-induced martensite transformation in 304 stainless steel reveals that the occurrence and magnitude of the martensite phase transformation increase depends on the stability of the austenite phase. By M in general_d30/50The tendency of the austenite phase to transform into the strain-induced martensite phase is evaluated by temperature, which means the temperature at which the martensite phase content reaches 30% at 50% strain. In other words, the martensite phase content can reach 30% when the material is deformed by 50% at this temperature. If M is_d30/50The higher the temperatureThe more unstable the austenite phase in the material, the more obvious the tendency of the material to undergo strain-induced martensitic transformation, wherein M is_d30/50＝580-520C-2Si-16Mn-23Ni-300N-26Cu-10Mo。

Substituting typical composition of 304 stainless steel into M_d30/50Temperature formula, calculating to obtain M_d30/50(304) Typical composition substitution of 50 ℃, 305 stainless steel into M_d30/50Temperature formula, calculating to obtain M_d30/50(305) At 27 ℃. As can be seen, M of 304_d30/50The temperature is high, so that strain-induced martensite phase transformation is easy to occur in the cold rolling process, and the material generates magnetism; 305 of M_d30/50The temperature is reduced by 23 c compared to 304 c, so that the strain-induced martensitic transformation occurs in a smaller amount than 304, since the nickel content in 305 is increased by 2% compared to 304 c. However, after adding 305 nickel, M_d30/50Compared with 304, the temperature is only reduced by 23 ℃, and the magnetism is generated when the deformation is slightly larger, thereby limiting the popularization and application of the material.

Aiming at the requirements of industries such as textile, electronics, instruments and meters, some related patents or researches have appeared, wherein the method mainly develops along two different directions (1) to improve the contents of Ni and Mn and increase the stability of austenite, so that the material does not generate a magnetic phase when deformed; (2) the Ni content is reduced, the austenite stability is increased through Mn and N alloying, so that the material does not generate a magnetic phase during deformation, and the cost is reduced. Ni is the most common element for stabilizing austenite, and the existing nonmagnetic stainless steel is a nickel-containing system.

Chinese patent CN93121570.6 discloses a novel austenite nonmagnetic stainless steel, which comprises the following chemical components: c is less than 0.12%, Si is less than 1.0%, Mn: 10-13%, P < 0.03%, S < 0.03%, Cr: 12-14%, Ni: 4-6%, Cu: 1.5-2.5%, Re < 0.02%, and the balance of Fe. The composition is characterized by containing rare earth elements, and the Cr content is far lower than 304; the addition of Mn and Cu is beneficial to reducing M_d30/50And the temperature is reduced or avoided, but the Ni is added by 4-6%, so that the cost is high.

Chinese patent CN90107850.6 discloses a single-phase austenite nonmagnetic stainless steel, which comprises the following chemical components: c is less than or equal to 0.08 percent, Si is less than or equal to 1.5 percent, Mn: 1.0-2.0%, Cr: 13.2-14.95%, Ni: 12.0-13.9%, Cu: 2.5-3.5%, P is less than or equal to 0.025%, S is less than or equal to 0.015%, Re: 0.005-0.05%, and the balance Fe. The material has stable matrix structure, is still a single-phase austenite structure after 20-80% of deformation, has stable magnetic permeability performance, but has the nickel content as high as 12.0-13.9%, so the material has excellent non-magnetic characteristic, but the cost is obviously increased.

Disclosure of Invention

The invention aims to provide a high-hardness non-magnetic nickel-free stainless steel and a manufacturing method thereof, wherein the steel material is in a full austenite mode (without delta phase formation) in a solidification process, the hardness of the steel reaches HV 425-497, the yield strength is 1100-1350 MPa, the content of a magnetic phase is 0%, the hardness and the strength are greatly improved, the steel is non-magnetic, the cost is obviously reduced, and the steel can be widely applied to industries requiring high hardness, wear resistance and non-magnetic property, such as textiles, electronics, instruments and the like.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a high-hardness non-magnetic nickel-free stainless steel comprises the following chemical components in percentage by weight: c: 0.15 to 0.20%, Si: 0.2-0.8%, Mn: 17.0-19.0%, Cr: 13.5-14.5%, N: 0.25-0.30%, Cu: 0.5-0.8%, B: 0.0015-0.0040% and the balance of Fe and inevitable impurities; and the above elements simultaneously need to satisfy the following relations:

C+N≥0.43％；

1.00≤(Cr+Mo+1.5Si)/(30N+30C+0.25Cu+0.5Mn)≤1.20；

580-520C-2Si-16Mn-23Ni-300N-26Cu-10Mo≤-100℃。

further, the chemical components of the high-hardness non-magnetic nickel-free stainless steel further comprise: one or two of V is less than or equal to 0.1 percent and Nb is less than or equal to 0.1 percent in percentage by weight.

The chemical components of the high-hardness non-magnetic nickel-free stainless steel also need to satisfy the following relationship: [0.021(Cr +0.9Mn) -0.204]/N is 1.50 or more.

The high-hardness non-magnetic nickel-free stainless steel has a fully austenitic structure in the process from the beginning to the end of solidification and at room temperature.

The high-hardness non-magnetic nickel-free stainless steel has the hardness of HV 425-497, the yield strength of 1100-1350 MPa and the content of a magnetic phase of 0%.

In the component design of the invention:

C. n (carbon, nitrogen): in the nickel-free system, carbon and nitrogen are strong austenite forming elements and can replace nickel to a certain extent, so that the austenite formation is promoted, the austenite structure is stabilized, and the M is remarkably reduced_d30/50And (3) temperature. Every 0.1% of C can be added to make M_d30/50(M_d30/50580-Si-16 Mn-23Ni-300N-26Cu-10Mo) temperature is lowered by 52 ℃, and M can be added by 0.1 percent of N_d30/50The temperature is reduced by 30 ℃, and the formation of a magnetic martensite phase in the strain process is effectively inhibited. However, when the contents of carbon and nitrogen are too high, chromium-rich carbides or nitrides are easily formed, resulting in intergranular corrosion. In addition, when the nitrogen content is too high, solidification pores are easily generated, and the deformation resistance is large and edge crack defects are easily generated during hot rolling. However, how to comprehensively control the C, N content in the nickel-free system is the key point of the invention. In the steel of the invention, C: 0.15-0.20%, N: 0.25-0.30% and C + N is more than or equal to 0.43%. Meanwhile, the solubility of nitrogen in the alloy is controlled to be more than 1.5 times of the actual nitrogen content, so that no risk of bubble generation in continuous casting is ensured, namely the [0.021(Cr +0.9Mn) -0.204 is controlled]/N≥1.50。

Si (silicon): silicon is a ferrite-forming and stabilizing element used for deoxidation during smelting, and silicon can improve the high-temperature strength of the ferrite phase. However, if the silicon content is too high, the solubility of nitrogen is lowered and the precipitation of intermetallic phases is accelerated. Therefore, the content of silicon in the steel is designed to be 0.2-0.8%.

Mn (manganese): manganese is an austenite forming and stabilizing element, can replace nickel to a certain extent by utilizing manganese to obtain an austenite structure, can obviously improve the solubility of nitrogen by adding manganese, and can also reduce M by adding manganese_d30/50At a temperature of 1% Mn, M can be added_d30/50The temperature was reduced by 16 ℃. Therefore, the content of Mn in the steel is controlled to be 17.0-19.0%.

Cr (chromium): chromium is the most important element for obtaining the corrosion resistance of steel, and higher chromium needs to be added for ensuring good corrosion resistance. However, chromium is the main ferrite forming element, and too high chromium causes a ferrite phase in the material, so that the full austenite solidification mode cannot be ensured. The content of Cr in the steel is controlled to be 13.5-14.5%, and the effect of improving the corrosion resistance by using N is utilized to assist in improving the corrosion resistance.

Cu (copper): copper is an austenite forming element and can improve the plasticity and corrosion resistance in reducing acids of stainless steel. But copper is also a relatively costly element. Therefore, the copper content in the steel is controlled to be 0.5-0.8%.

V (vanadium), Nb (niobium): vanadium and niobium are selected as optional elements, the main functions are to refine the structure, improve the purity of molten steel and improve the hot-working performance, and the content of the vanadium and the niobium is controlled below 0.1 percent.

B (boron): the invention has poor hot processing performance due to no nickel and high C, N, and the edge crack and the scrap of the steel coil are easy to cause during hot rolling. The addition of boron can refine the structure, improve the grain boundary strength and improve the thermoplasticity, but excessive boron can cause the hot workability of the material to be deteriorated, so the invention discovers that the optimal hot workability can be obtained by adding 0.0015% to 0.0040% of B in the alloy system.

In the chemical components of the invention, the ratio of C + N is controlled to be more than or equal to 0.43 percent, and the ratio of (Cr + Mo +1.5Si)/(30N +30C +0.25Cu +0.5Mn) is controlled to be more than or equal to 1.20: the ferrite phase, namely the full austenite solidification, is not generated in the process from the beginning to the end of the solidification of the steel material, and the phenomenon of cracking caused by excessive growth of crystal grains is avoided.

At the same time, the invention controls M_d30/50The temperature is less than or equal to-100 ℃, the austenite has high stability, and when the deformation hardening or forming is 65%, the deformation mode of the material is twin crystal or dislocation multiplication, no martensite phase transformation is generated, and therefore no martensite phase is generated.

The invention relates to a manufacturing method of high-hardness non-magnetic nickel-free stainless steel, which comprises the following steps:

(1) smelting according to the components, and casting into a casting blank, wherein the superheat degree is less than or equal to 35 ℃ during casting; then forging or hot rolling, wherein the heating temperature is 1180-1230 ℃; then annealing and acid washing are carried out;

(2) carrying out cold rolling, annealing after cold rolling and acid pickling on the steel plate obtained in the step 1), wherein the annealing temperature after cold rolling is 1100-1130 ℃; and then, performing temper rolling, wherein the reduction rate is controlled to be 40-65%.

The superheat degree is controlled to be less than or equal to 35 ℃ during casting so as to avoid cracks caused by grain growth in a full austenite solidification mode; and controlling the heating temperature to 1180-1230 ℃ in the forging or hot rolling process, so as to avoid cracks caused by the growth of crystal grains.

The annealing temperature after cold rolling is controlled to be 1100-1130 ℃: the reason is that the carbon content in the nickel-free component system is 0.15-0.20%, the precipitation amount of the carbide is large, and the carbide can be fully dissolved at a high annealing temperature after cold rolling. Insufficient solid solution of carbide will result in a decrease in the corrosion resistance of the material. More critically, if carbon is present in the form of carbides rather than as solid solutions, it does not contribute to the stability of the austenite and does not ensure that the austenite phase remains stable during cold-strain.

Through the cold-working deformation, the strength and the hardness of the material are improved, wherein the hardness can reach HV 425-497, and particularly 0% of a magnetic phase in the cold-working deformation process is ensured. The high hardness of the steel grade comes from solid solution strengthening and temper rolling in component design. However, the invention is different from the conventional deformation hardening, and the invention leads the hardening to be derived from dislocation + twin crystal by matching special component design and reduction rate, but not from the dislocation + martensite phase transformation of the conventional austenitic stainless steel. However, when the reduction ratio is too large, the composition of the present invention may cause martensitic transformation with the accumulation of strain. Therefore, the invention controls the reduction rate to be 40-65% by matching with a component system.

According to the invention, C, N element is used to replace Ni element, so that austenite structure at room temperature is obtained, and the content of expensive Ni element is effectively reduced, thereby reducing the cost; meanwhile, M is remarkably reduced by using C, N and other elements_d30/50Temperature, improving stability of austenite phase, and inhibiting generation of strain-induced martensite phase; c, N as a solid solution strengthening element itself can also improve the strength and hardness of the material.

The full austenite solidification mode is one of the core innovation points of the invention. Existing austenitic stainless steels are substantially solidified in a delta ferrite + austenite manner, while the delta phase is a magnetic phase (equivalent to a magnetically conductive phase). Even if the subsequent hot working process can reduce the δ -phase ratio, it is difficult to completely eliminate it. The invention provides a design principle for controlling a full austenite solidification mode in a component system, and can ensure no nickel when controlling the Cr equivalent/Ni equivalent to be less than or equal to 1.20, so that the full austenite solidification mode containing Mn and N component system is designed and obtained, and the full austenite solidification mode has the excellent characteristics of high-temperature solidification and full non-magnetism and low-temperature cold processing and full non-magnetism.

The invention adopts two ways to obtain high hardness: solid solution strengthening, wherein C + N in the material is controlled to be more than or equal to 0.43 percent, and the yield strength can be improved by more than 300MPa by the solid solution strengthening. And (3) performing deformation hardening, namely rolling the material with the reduction rate of 40-65%, and performing deformation strengthening to obtain high hardness. Provided however that M of the material_d30/50580-Si-16 Mn-23Ni-300N-26Cu-10Mo is less than or equal to-100 ℃, and austenite of the material has high stability and does not generate a magnetic-conductive martensite phase during cold deformation. Finally, high hardness of HV 425-497 is obtained under the condition of no nickel.

The material of the invention has no delta phase in the solidification process, the solidification mode is full austenite solidification, and the material does not generate a magnetic phase from solidification to room temperature. And M of steel material_d30/50The temperature is less than or equal to-100 ℃, and the material is ensured not to generate martensite phase transformation and magnetic phase in the process of deforming the material into parts such as buttons, zippers and the like. Meanwhile, the material is nickel-free, and the cost is lower than that of 304 or the existing non-magnetic stainless steel by more than 20%.

The element symbols in the formula and the relational expression related by the invention represent the weight percentage content of the corresponding elements multiplied by 100.

Compared with the prior art, the invention has the beneficial effects that:

(1) non-magnetic property: according to the invention, through the component design of full austenite solidification and high austenite stability, a delta phase without magnetic conductivity is generated during high-temperature solidification, and a martensite phase without magnetic conductivity is generated during room-temperature deformation. Meanwhile, the high austenite stability ensures that the material does not generate a magnetic conduction phase when being bent, formed or processed in the using process, namely, the material maintains the non-magnetic characteristic.

(2) High hardness: according to the invention, on the basis of C, N solid solution strengthening, the hardness and strength are further improved through deformation strengthening, so that the hardness of the material at room temperature reaches HV 425-497, the yield strength is 1100-1350 MPa, the elongation is not less than 5%, and the material is non-magnetic. When in use, the steel material of the invention keeps no magnetic conductive phase generated in the forming process of processing parts.

Compared with the conventional steel 304 (the hardness is HV 180, and the yield strength is 280MPa), the hardness and the strength of the steel are improved by 3-4 times, the wear resistance and the rigidity are also obviously improved, and the performances are established on the premise of no magnetism. The conventional 304 can also be strengthened through deformation, but a magnetic conducting phase is generated in the deformation strengthening process of the conventional 304, so that the requirement of no magnetism is not met.

(3) No nickel: the steel does not contain nickel, the content of copper is controlled to be low, demagnetization heat treatment after deformation is not needed, the cost is obviously reduced and is far lower than that of 304 or nickel-containing steel, and the steel is suitable for civil fields such as textile and the like;

on the other hand, the invention does not add noble nickel elements, but has the excellent characteristics of high-temperature solidification and low-temperature cold processing, and is also one of the innovations of the invention.

Drawings

Fig. 1 is a graph illustrating the change of hardness and content of magnetic conductive phase during cold deformation of the prior art 304 (i.e., comparative example 1).

FIG. 2 is a schematic diagram showing the change of phase content during solidification in example 3 of the present invention.

FIG. 3 is a schematic diagram showing the change of phase content during solidification in comparative example 1.

Fig. 4 is a schematic diagram showing the change of phase content during solidification in comparative example 2.

Fig. 5 is a schematic diagram showing the change of phase content during solidification in comparative example 3.

Detailed Description

The invention is further illustrated by the following examples and figures.

Table 1 shows the composition of the steels of examples of the present invention and comparative examples, and table 2 shows the key process parameters and properties of the steels of examples of the present invention and comparative examples.

The embodiment of the invention takes the production flow of electric furnace-AOD smelting as an example: adding ferrochrome, ferronickel, scrap steel and the like into an electric furnace for melting, pouring molten steel into an AOD furnace after melting down, performing blowing of removing C, removing S, increasing N and controlling N in the AOD furnace, pouring the molten steel into a tundish when smelting components meet requirements, and casting on a vertical bending type continuous casting machine. The superheat degree of continuous casting is below 35 ℃, the plate blank drawing speed is 0.8-1.3 m/min, and the uniform structure and no pore defect under the full austenite solidification are ensured. And (3) putting the continuous casting plate blank into a roller hearth type heating furnace, heating to 1180-1230 ℃, rolling to the required thickness on a hot continuous rolling mill set, and then coiling. And then carrying out continuous acid pickling annealing at the annealing temperature of 1100-1130 ℃ to ensure that the carbide is fully dissolved. Then performing deformation hardening rolling with the rolling reduction rate of 40-65%.

And detecting the content of the magnetic conduction martensite phase in different materials by using a magnetic tester. The mechanical properties are all taken from cold-rolled sheets, processed and tested by adopting JIS 13B standard. The mechanical properties of the inventive steels and the comparative steels are examined in table 2.

As can be seen from fig. 2, in example 3 of the present invention, no ferrite phase is completely generated from the start of solidification to the end of solidification, and the solidification mode is that the liquid phase is directly transformed into the austenite phase; as can be seen from fig. 3, 4 and 5, comparative examples 1, 2 and 3 are all the ferrite phase + austenite phase precipitation modes, i.e., a portion of the ferrite phase is precipitated first, and the ferrite phase can be gradually transformed into the austenite phase during the temperature reduction process, but cannot be completely eliminated, and a portion of the ferrite phase remains to room temperature.

As can be seen from Table 2, the examples of the present invention all maintained the magnetic phase content at 0, i.e., maintained the completely nonmagnetic characteristic, when the hardness reached HV 425-497. In comparative example 1, when the hardness reached HV 413 and 441, the magnetic phase contents reached 22.5% and 29.9%, the material became a permeable material remarkably, and the proportion of the magnetic phase increased with the increase in the hardness, failing to satisfy the use for no magnetism. In comparative example 2, when the hardness reaches HV 422, 435 and 455, the magnetic phase contents reach 0.9%, 1.6% and 2.0%, respectively, and the magnetic material also becomes a magnetic conductive material, and cannot meet the application requirements of complete non-magnetism. Comparative example 3 has the magnetic phase content maintained at 0 when the hardness reaches HV 428 and 447, but the nickel content of the steel grade in comparative example 3 reaches 4.5%, which is a nickel-containing nonmagnetic steel composition system and has a high nickel content, while the examples in the present invention do not contain nickel, and are a new composition system completely free of nickel, and have materials with low cost and excellent performance.

As can be seen from the table 1-2, the hardness of the steel material disclosed by the invention reaches HV 425-497 degrees, the yield strength is 1100-1350 MPa, the elongation is more than or equal to 5%, and the steel material has the characteristics of high hardness and complete no magnetism; while utilizing C, N, Mn to reduce M_d30/50Temperature, M of the material_d30/50The temperature is reduced to below-100 ℃. The material is processed by deformation hardening, has high strength and high hardness, and can meet the requirements of textile industry, electronic industry and the like on the mechanical property of the material. Meanwhile, because the stability of the austenite phase is improved, the hardening of the material is mainly generated by work hardening, namely, the generation and the accumulation of dislocation and twin crystal, but the magnetic martensite phase is not generated, and the nonmagnetic characteristic of the hard material is ensured. Meanwhile, the steel material of the invention does not contain noble nickel element, has lower cost, and can be widely applied to the fields of textile, electronic instruments, equipment and the like which require high hardness, low cost and no magnetism.

Claims

1. A high-hardness non-magnetic nickel-free stainless steel comprises the following chemical components in percentage by weight: c: 0.15 to 0.20%, Si: 0.2-0.8%, Mn: 17.0-19.0%, Cr: 13.5-14.5%, N: 0.25-0.30%, Cu: 0.5-0.8%, B: 0.0015-0.0040% and the balance of Fe and inevitable impurities; and the above elements simultaneously need to satisfy the following relations: c + N is more than or equal to 0.43 percent; (Cr + Mo +1.5Si)/(30N +30C +0.25Cu +0.5Mn) is more than or equal to 1.00 and less than or equal to 1.20; 580-520C-2Si-16Mn-23Ni-300N-26Cu-10Mo is less than or equal to-100 ℃; [0.021(Cr +0.9Mn) -0.204]/N is 1.50 or more.

2. The high-hardness non-magnetic nickel-free stainless steel according to claim 1, further comprising chemical components of: one or two of V is less than or equal to 0.1 percent and Nb is less than or equal to 0.1 percent in percentage by weight.

3. The high-hardness non-magnetic nickel-free stainless steel according to any one of claims 1 to 2, wherein the high-hardness non-magnetic nickel-free stainless steel has a fully austenitic structure from the start of solidification to the end of solidification and at room temperature.

4. The high-hardness non-magnetic nickel-free stainless steel according to claim 1 or 2, wherein the high-hardness non-magnetic nickel-free stainless steel has hardness of HV 425-497, yield strength of 1100-1350 MPa, and magnetic phase content of 0%.

5. A manufacturing method of high-hardness non-magnetic nickel-free stainless steel comprises the following steps: 1) smelting according to the chemical components of any one of claims 1 to 2, and casting into a casting blank, wherein the superheat degree during casting is less than or equal to 35 ℃; then forging or hot rolling, wherein the heating temperature is 1180-1230 ℃; then annealing and acid washing are carried out; 2) carrying out cold rolling, annealing and acid pickling on the steel plate obtained in the step 1), wherein the annealing temperature is 1100-1130 ℃; and then, performing temper rolling, wherein the reduction rate is controlled to be 40-65%.

6. The method of manufacturing a high-hardness non-magnetic nickel-free stainless steel according to claim 5, wherein the high-hardness non-magnetic nickel-free stainless steel has a fully austenitic structure in the period from the start of solidification to the end of solidification and at room temperature.

7. The method for manufacturing a high-hardness non-magnetic nickel-free stainless steel according to claim 5, wherein the high-hardness non-magnetic nickel-free stainless steel has a hardness of HV425 to 497, a yield strength of 1100 to 1350MPa, and a magnetic phase content of 0%.