阅读说明：本技术 具有超低温冲击韧性的高锰奥氏体钢及其热轧板制造方法 (High manganese austenitic steel with ultralow-temperature impact toughness and manufacturing method of hot rolled plate thereof ) 是由 范勇斐 张恒 赵欣 续维 于 2018-07-17 设计创作，主要内容包括：本发明公开了一种具有超低温冲击韧性的高锰奥氏体耐磨钢,按质量百分比计包含：C：0.15～0.42％,Si：0.15～0.60％,Mn：25～33％,P：≤0.045％,S：≤0.03％,Cr：2～5％,Ni：≤3％,Mo：≤0.5％,V：0.30～0.50％,Cu：≤0.5％,Al≤2％,其余为铁和不可避免的杂质,并且在Cr含量为2～5％范围内时,Mn和C的含量需满足Mn+35C＝37～40％。本发明还公开了该奥氏体耐磨钢的热轧板制备方法。本发明通过采用一定比例的高锰低碳的成分组合,能显著提高低温高锰钢的超低温冲击韧性,实现高锰钢的连铸热轧生产,降低生产成本,稳定产品质量的目的。(The invention discloses a high manganese austenite wear-resistant steel with ultralow temperature impact toughness, which comprises the following components in percentage by mass: c: 0.15 to 0.42%, Si: 0.15 to 0.60%, Mn: 25-33%, P: less than or equal to 0.045%, S: less than or equal to 0.03 percent, Cr: 2-5%, Ni: less than or equal to 3 percent, Mo: less than or equal to 0.5 percent, V: 0.30-0.50%, Cu: not more than 0.5 percent, not more than 2 percent of Al, and the balance of iron and inevitable impurities, and when the content of Cr is within the range of 2-5 percent, the content of Mn and C is required to meet the requirement that Mn +35C is 37-40 percent. The invention also discloses a preparation method of the hot rolled plate of the austenitic wear-resistant steel. The invention adopts the composition combination of high manganese and low carbon in a certain proportion, can obviously improve the ultralow temperature impact toughness of the low-temperature high manganese steel, realizes the continuous casting and hot rolling production of the high manganese steel, reduces the production cost and stabilizes the product quality.)

1. An austenitic wear-resistant steel having ultra-low temperature impact toughness, characterized by comprising, in mass percent: c: 0.15 to 0.42%, Si: 0.15 to 0.60%, Mn: 25-33%, P: less than or equal to 0.045%, S: less than or equal to 0.03 percent, Cr: 2-5%, Ni: less than or equal to 3 percent, Mo: less than or equal to 0.5 percent, V: 0.30-0.50%, Cu: not more than 0.5 percent, not more than 2 percent of Al, and the balance of iron and inevitable impurities, and when the content of Cr is within the range of 2-5 percent, the content of Mn and C is required to meet the requirement that Mn +35C is 37-40 percent.

2. The method of making a hot rolled plate of austenitic wear resistant steel as claimed in claim 1, wherein the method comprises the steps of:

firstly, alloy proportioning is carried out, then electric furnace steelmaking, external refining, continuous casting, hot feeding, reheating, hot rolling, solid solution after rolling are carried out in sequence,

in the reheating step, the heating temperature of the plate blank is controlled to be 1120-1250 ℃;

in the hot rolling step, the initial rolling temperature of the plate blank is controlled to be 1050-1200 ℃, and the final rolling temperature of the plate blank is controlled to be 950-1100 ℃.

3. The method of making a hot rolled plate of austenitic wear resistant steel as claimed in claim 2, wherein: in the solid solution step after rolling, the solid solution starting temperature is controlled to be 900-1100 ℃; the solid solution termination temperature is controlled to be less than or equal to 500 ℃, and the cooling speed is controlled to be 10-50 ℃/S.

4. The method of making a hot rolled plate of austenitic wear resistant steel as claimed in claim 2, wherein: the continuous casting adopts vertical continuous casting.

Technical Field

The invention relates to wear-resistant steel, in particular to high manganese austenitic steel with ultralow-temperature impact toughness and a manufacturing method of a hot rolled plate thereof.

Background

Natural gas is a high-quality energy source, the main component of the natural gas is methane, and the natural gas has the characteristics of high combustion heat value and less pollution. In recent thirty years, with the continuous improvement of environmental protection requirements, natural gas is increasingly emphasized by people and widely applied to power generation, automobile fuel, resident life and industry. The liquid formed by the condensation of gaseous Natural Gas at atmospheric pressure cooled to below-162 ℃ is called Liquefied Natural Gas (LNG). Compared with the gaseous natural gas, the liquefied natural gas only has 1/625 of the original volume, so that the liquefied natural gas is very convenient to store and transport on the ground, and the ground transportation cost of the liquefied natural gas in unit weight is only 1/6-1/7 of the pipeline transportation cost. In addition to the use of heat energy, the ultralow temperature LNG can provide a large amount of cold energy (121 kcal/kg of latent heat of vaporization) in the process of converting to a normal temperature gas state under atmospheric pressure, and can be recovered and used for other low temperature applications.

Since the storage and transportation temperature of the liquefied natural gas is below-162 ℃ (natural gas atmospheric boiling point), the material for storing and transporting the liquefied natural gas is required to have good impact toughness and sufficient brittle cracking resistance and crack arrest capability at ultralow temperature. And less materials meeting the mechanical property requirement at low temperature can be selected below-162 ℃. At present, 9Ni steel is mainly used as a material for constructing LNG storage and transportation facilities in the world, and a novel ultralow temperature material is also being developed. Of these, high manganese austenitic steels are of interest due to their remarkable advantages in price, low coefficient of thermal expansion and low cycle fatigue properties. The high manganese austenitic steel adopts manganese and carbon to stabilize an austenite phase, obtains a single-phase austenite structure at room temperature, generally has no ductile-brittle transition phenomenon, and has the inherent advantages of ultralow temperature (-196 ℃) application.

Domestic patent 89104759.X provides an iron-manganese-aluminum-carbon austenite nonmagnetic steel and a low temperature steel, which comprises the following components in percentage by weight: c: 0.25 to 0.33%, Si: less than or equal to 0.7 percent, Mn: 19-21%, P: less than or equal to 0.04 percent; s: less than or equal to 0.05 percent, Al: 2.3-3.2, and the balance of iron and inevitable impurities, and is mainly smelted by an electric arc furnace oxidation method (or smelting by an induction furnace), an alkaline liquid slag is used for protecting ingots, a steel ingot is heated to about 1200 ℃, and is processed into a profile at the temperature of 1150-800 ℃, and the solid solution temperature is 1000 +/-50 ℃. The steel has extremely low magnetic conductivity and high toughness at-196 ℃ and above, can replace 1Cr18Ni9Ti and 9% Ni steel to be used for mechanical parts of low-temperature equipment at-196 ℃ and above, such as containers, valves and the like, and has low price and simple heat treatment process and welding process.

Domestic patent 201710359159.6 provides a design and manufacturing method of a high-manganese medium plate for an LNG storage tank, and the steel comprises the following chemical components in percentage by weight: c: 0.45-0.67%, Si: 0.02 to 0.48%, Mn: 23.70-27.20%, P: less than or equal to 0.051 percent; s: not more than 0.02 percent, not more than 2.20 percent of Ni, not more than 4.13 percent of Cr, not more than 1.10 percent of Cu, not more than 0.94 percent of Mo, not more than 0.21 percent of V, Al: less than or equal to 4.64 percent, the balance of iron and inevitable impurities, the steel is a single-phase austenite structure, has high strength and plasticity, simultaneously has excellent-196 ℃ ultralow temperature impact toughness, can replace 9 percent Ni steel, and has the cost far lower than 9 percent Ni steel.

US20060084305 shows a high manganese austenitic stainless steel for high pressure hydrogen, the chemical composition of the steel being wt%: c: 0.01-0.10%, Si: 0.1-1%, Mn: 6-20%, 1-6% of Ni, 10-20% of Cr, 2-5% of Cu, and N: 0.01-0.40 percent, and the balance of iron and inevitable impurities, wherein the steel is a single-phase austenite structure, Md30 of the steel meets the requirement that-120 is more than Md30 and less than 20, and Md30 is 497-.

JP19990318357 shows a high manganese non-magnetic steel for ultralow temperature, the chemical components of the steel are wt%: c: 0.05-0.15%, Mn: 26.0 to 30.0%, 0.50 to 5.0% of Ni, 5.0 to 10.0% of Cr, N: 0.05-0.15 percent of steel, and the balance of iron and inevitable impurities, and the steel grade has ultralow temperature toughness and is suitable for low-temperature environments.

KR19890020003 shows a high manganese steel and a manufacturing method thereof, wherein the steel comprises the following chemical components in percentage by weight: c: 0.1-0.5%, Si: 0.02 to 1.5%, Mn: 16-35%, Al 1-8%, Ti 0.02-0.15%, Nb 0.05-0.15%, Cu: less than or equal to 0.5 percent, and the balance of iron and inevitable impurities.

KR19960077693 shows a high manganese steel with excellent ultra-low temperature toughness and its manufacturing method, the chemical composition of the steel is wt%: c: 0.45-0.55%, Si: 0.4-0.8%, Mn: 16-22%, Ni: 1.5-4%, Cr: 2-5.5%, Mo: 0.1-0.3%, Al 1-2.5%, Cu: 0.1-0.2%, and the balance of iron and inevitable impurities.

In the above patent documents, the design concept mainly focuses on the properties such as strength and toughness of the material, but no intensive research has been conducted on the relationship between the components and the optimization of the ultra-low temperature toughness. In addition, the above patent products are less related to the continuous casting and hot rolling production process.

Disclosure of Invention

The invention aims to solve the defects and provides the high manganese austenitic steel with corrosion resistance, abrasion resistance and ultralow temperature impact toughness and the manufacturing method of the hot rolled plate thereof.

In order to achieve the above object, the present invention adopts the following technical solutions.

In one aspect, an austenitic wear resistant steel having resistance to corrosive wear comprises, in mass percent: c: 0.15 to 0.42%, Si: 0.15 to 0.60%, Mn: 25-33%, P: less than or equal to 0.045%, S: less than or equal to 0.03 percent, Cr: 2-5%, Ni: less than or equal to 3 percent, Mo: less than or equal to 0.5 percent, V: 0.30-0.50%, Cu: not more than 0.5 percent, not more than 2 percent of Al, and the balance of iron and inevitable impurities, and when the content of Cr is within the range of 2-5 percent, the content of Mn and C is required to meet the requirement that Mn +35C is 37-40 percent.

In another aspect, a method for producing a hot-rolled plate of austenitic wear-resistant steel having resistance to corrosive wear, comprises the steps of:

firstly, alloy proportioning is carried out, then electric furnace steelmaking, external refining, continuous casting, hot feeding, reheating, hot rolling, solid solution after rolling are carried out in sequence,

in the reheating step, the heating temperature of the plate blank is controlled to be 1120-1250 ℃;

in the hot rolling step, the initial rolling temperature of the plate blank is controlled to be 1050-1200 ℃, and the final rolling temperature of the plate blank is controlled to be 950-1100 ℃.

In the solid solution step after rolling, the solid solution starting temperature is controlled to be 900-1100 ℃; the solid solution termination temperature is controlled to be less than or equal to 500 ℃, and the cooling speed is controlled to be 10-50 ℃/S.

The continuous casting adopts vertical continuous casting.

The high manganese austenitic steel with ultralow temperature impact toughness and the manufacturing method of the hot rolled plate thereof have the following advantages:

1. compared with the prior art patent documents, the invention provides reasonable element proportions of C, Mn and Cr, and simultaneously inhibits the precipitation and growth of carbide and improves the ultralow temperature toughness of high manganese steel at the same austenite stability through alloying treatment.

2. Through the optimization of alloy elements, the high-temperature strength and the heat conductivity coefficient of the high-manganese steel are improved, and the thermal expansion coefficient of the high-manganese steel is reduced, so that the continuous casting production difficulty and the rolling difficulty are reduced.

3. The invention adopts the vertical continuous casting and hot feeding hot rolling process to realize the production of hot rolled plate products. For high manganese steel (with manganese content more than 20%), the thermal expansion coefficient is large, the thermal conductivity is low, and the production cannot be carried out by a common vertical bending type continuous casting machine. The casting blank produced by the vertical continuous casting machine has greatly improved solidification segregation, uniform structure, greatly improved continuous casting blank inclusion, high purity and greatly improved surface quality. Meanwhile, the rolling is carried out in a reasonable rolling temperature range, and a solution treatment process after rolling is adopted, so that the hot rolled plate product is ensured to have the best tissue state, surface quality and service performance, the production efficiency is improved, and the production cost is reduced.

Drawings

FIG. 1 is a metallographic photograph of an austenitic wear-resistant steel in example 1 of the present invention.

Detailed Description

The technical scheme of the invention is further explained by combining the attached drawings.

The component design idea of the austenitic wear-resistant steel with the corrosion and wear resistance is to improve the ultralow-temperature impact toughness of low-temperature austenite by alloying treatment under the condition that the stability of the austenitic steel is not changed. Meanwhile, the vertical continuous casting process is adopted to improve the solidification segregation and surface quality of steel ingots, improve the structure uniformity and the molten steel purity, and the solid solution process after rolling is combined to obtain an austenite structure, so that the ultralow-temperature impact toughness of the manganese steel is improved. The method comprises the following specific steps:

the austenitic wear-resistant steel comprises the following components in percentage by mass: c: 0.15 to 0.42%, Si: 0.15 to 0.60%, Mn: 25-33%, P: less than or equal to 0.045%, S: less than or equal to 0.03 percent, Cr: 2-5%, Ni: less than or equal to 3 percent, Mo: less than or equal to 0.5 percent, V: 0.30-0.50%, Cu: not more than 0.5 percent, not more than 2 percent of Al, and the balance of iron and inevitable impurities, and when the content of Cr is within the range of 2-5 percent, the content of Mn and C is required to meet the requirement that Mn +35C is 37-40 percent.

The main alloy elements have the following functions:

carbon: carbon is one of the main elements constituting high manganese steel. Carbon stabilizes the austenite in the alloy and, when rapidly cooled, maintains the austenite in a single phase at room temperature. The solid solution strengthening effect of carbon is enhanced as the carbon content is increased, so that the hardness, strength and wear resistance of the high manganese steel are improved. But the carbon content is continuously increased, the carbide content in the high manganese steel structure is increased, and the carbide content is probably distributed along the grain boundary, so that the impact toughness of the steel is greatly reduced. And because the specific volume of carbide is different from that of austenite, the high manganese steel after solid solution has the defect of extremely small holes, and the impact toughness of the steel is also reduced. Generally, the carbon content of the high manganese steel is controlled to be 0.3-1.0%, and the C content of the high manganese steel is 0.15-0.42%.

Manganese: manganese is a main component of high manganese steel, and has great influence on the expansion of an alloy phase region, the stability of an austenite structure and the reduction of an Ms point, and the manganese can keep the austenite structure of the high manganese steel to room temperature. If the content of manganese is increased, the strength and impact toughness of the high manganese steel are improved because manganese has an effect of increasing intercrystalline bonding. If the content of manganese is very high, the thermal conductivity of the steel is reduced, and then a transgranular structure is easy to appear, so that the mechanical and mechanical properties of the high manganese steel are seriously influenced. In the invention, the alloying influence is considered, and the Mn content control interval is 25-33%.

Carbon-manganese combination: in the austenitic high manganese steel of the present invention, carbon and manganese are both main elements, and the carbide content therein seriously affects the impact toughness and strength of the austenitic steel, and the higher the carbon content and the manganese content, the higher the carbide content in the structure. Experiments show that in order to ensure the ultralow-temperature impact toughness of the high-manganese steel, when the content of the alloy elements is within the range of the invention, particularly when the content of chromium is 2-5%, the content of Mn and the content of C need to meet the requirement that Mn +35C is 37-40.

Silicon: silicon is usually introduced as a deoxidizer, and has the effects of strengthening solid solution and improving yield strength. But it closes the phase region and promotes graphitization. When the content is more than 0.6 percent, on one hand, the high manganese steel generates coarse grains, and on the other hand, the solubility of carbon in austenite is reduced, so that the precipitation of carbide in grain boundaries is promoted, the toughness of the steel is reduced, and the hot cracking tendency of the steel is increased. Therefore, silicon is usually controlled to be in the range of 0.3-0.6%, but in some special cases, if the molten steel has good fluidity, the amount of silicon should be increased to improve the condition of the grain boundary. The silicon content of the invention is controlled to be 0.15-0.60%.

Sulfur: because of the existence of sulfur and manganese in the high manganese steel, manganese sulfide is generated, and can enter the slag. Therefore, the sulfur content of the invention is controlled below 0.03 percent

Phosphorus: the solubility in austenite is small, and eutectic phosphide is usually generated with iron, manganese and the like, and is precipitated at grain boundaries. Phosphorus and lead to thermal cracking of the material, reducing the mechanical properties of the material and causing some deterioration in wear resistance, and in severe cases even during operation. In addition, phosphorus also has the function of promoting the segregation of manganese and carbon elements, and the content of phosphorus should be reduced as much as possible. The phosphorus content of the invention is controlled below 0.045%.

Chromium: chromium is a relatively large element currently used in high manganese steel and also has an obvious effect on corrosion resistance. Most of chromium is dissolved into austenite of the high manganese steel after the water toughening treatment, so that the stability and the corrosion resistance of the high manganese steel are improved, and the precipitation of carbide during cooling is accelerated. After chromium is dissolved in austenite, the yield strength of the steel can be improved, and the elongation and impact toughness of the steel can be reduced. During production, if chromium is increased in the as-cast state, precipitation of carbides is also accelerated, and a continuous network distribution is generally performed at grain boundaries. When reheating is carried out, the austenite is relatively difficult to dissolve, so that single-phase austenite is difficult to obtain, and the temperature for heating the water toughness is increased by 30-50 ℃ on the basis of standard high manganese steel. The addition amount of Cr is 2-5%.

Nickel: nickel is a non-carbide forming element and is also an austenite forming element, the corrosion resistance and the low-temperature toughness of the high manganese steel can be improved, but the cost is high, so the addition amount of Ni is less than or equal to 3 percent.

Molybdenum: the binding force of molybdenum and iron is strong, and the size of molybdenum atoms is large and the diffusion speed is low, so that the precipitation amount of carbides in the molybdenum-added cast high-manganese steel is reduced, the austenite grain boundary does not present a net shape any more, the precipitation speed of the needle-shaped carbides in the steel can be reduced, the precipitation temperature is reduced, and the molybdenum-iron alloy is beneficial to improving the plasticity and strength of the high-manganese steel in an as-cast state, and the defects caused by the addition of chromium elements are well made up. Therefore, it is very beneficial to add molybdenum to the chromium-containing high manganese steel. The invention considers the alloying effect, and the Mo content is designed and controlled below 0.50 percent.

Vanadium: the vanadium has the functions of refining the structure of the high manganese steel and improving the yield strength, the original hardness and the wear resistance of the steel. Vanadium is a strong carbide forming element, VC or V (C, N) is firstly precipitated in the solidification process, the carbides are dispersed and distributed to have the function of strongly inhibiting the growth of crystal grains, and the formation and growth of grain boundary carbides are also inhibited by the intragranular precipitation of the carbides. However, when the amount of V added is too large, coarse liquated carbides are easily formed, and the impact toughness of the steel is lowered. When the amount of V added is too small, the effect of refining crystal grains is not obtained. In the invention, the alloying influence is considered, and the design of the V content is controlled to be below 0.30-0.50%.

Copper: copper is a non-carbide forming element and is also an austenite forming element, and the corrosion resistance and the low-temperature toughness of the high manganese steel can be improved, so that the Cu adding amount is controlled to be below 0.50 percent.

Aluminum: aluminum is a ferrite-forming element and increases the stacking fault energy of austenite. Therefore, the Al content of the invention is controlled below 2%.

The preparation method of the hot rolled plate of the austenitic wear-resistant steel comprises the following steps:

the method comprises the following steps:

firstly, alloy proportioning is carried out, then electric furnace steelmaking, external refining, continuous casting, hot feeding, reheating, hot rolling, solid solution after rolling are carried out in sequence,

in the reheating step, the heating temperature of the plate blank is controlled to be 1120-1250 ℃;

in the hot rolling step, the initial rolling temperature of the plate blank is controlled to be 1050-1200 ℃, and the final rolling temperature of the plate blank is controlled to be 950-1100 ℃.

In the solid solution step after rolling, the solid solution starting temperature is controlled to be 900-1100 ℃; the solid solution termination temperature is controlled to be less than or equal to 500 ℃, and the cooling speed is controlled to be 10-50 ℃/S.

The continuous casting is preferably vertical continuous casting.

The invention is shown in table 1 in comparison with the components of the prior art, and comparative examples 1-6 in table 1 are 89104759.X, 201710359159.6, US20060084305, JP19990318357, KR19890020003 and KR19960077693 in sequence.

TABLE 1 comparison of the ingredients of the present invention with those of the similar patents at home and abroad

Compared with the prior production steel grade, the performance of the austenitic high manganese steel of the invention can reach the following requirements:

1. mechanical properties: sigma b is more than or equal to 750MPa, sigma 0.2 is more than or equal to 350MPa, elongation is more than or equal to 20 percent, Brinell hardness is less than or equal to 230

2. Charpy notched impact performance: the impact energy at room temperature is more than or equal to 100J, and the impact energy at the temperature of-196 ℃ is more than or equal to 40J.

The main chemical components of examples 1 to 6 of the present invention are shown in Table 2:

TABLE 2 chemical composition (%)