阅读说明：本技术 一种钢轨用钢及其生产方法 (Steel for steel rail and production method thereof ) 是由 刘丹 李建朝 李�杰 龙杰 刘生 袁平 付振坡 付冬阳 赵晓辉 师帅 于 2020-07-16 设计创作，主要内容包括：本发明公开了一种钢轨用钢及其生产方法,钢板化学成分组成及质量百分含量为：C：0.74～0.86%、Si：1.1～1.4%、P≤0.025%、S≤0.025%、Mn：0.8～1.2%、Cu：0.5～0.7%,其余为Fe和不可避免的杂质元素；生产方法包括加热、轧制以及热处理工序,其中热处理工序采用回火方式。本发明通过合理成分和工业设计,所得钢板强度、延伸率高但表面硬度低,能够在极冷天气下使用。本发明提供的钢板组织类型为回火马氏体+铁素体(少量),钢板抗拉强度Rm≥900MPa、A<Sub>50</Sub>≥9%、常温冲击韧性在30J以上,硬度HB≤300,钢板最大厚度230mm,可供车用轨道、地铁轨道使用。(The invention discloses steel for a steel rail and a production method thereof, wherein the steel plate comprises the following chemical components in percentage by mass: c: 0.74-0.86%, Si: 1.1-1.4%, P is less than or equal to 0.025%, S is less than or equal to 0.025%, Mn: 0.8 to 1.2%, Cu: 0.5-0.7% of Fe and inevitable impurity elements as the rest; the production method comprises the working procedures of heating, rolling and heat treatment, wherein the heat treatment adopts a tempering mode. Through reasonable components and industrial design, the obtained steel plate has high strength and elongation but low surface hardness, and can be used in extremely cold weather. The steel plate provided by the invention has the structure types of tempered martensite and ferrite (a small amount), the tensile strength Rm of the steel plate is more than or equal to 900MPa, A 50 The steel plate has the impact toughness at normal temperature of more than 30J, the hardness HB of less than or equal to 300 and the maximum thickness of 230mm, and can be used for vehicle tracks and subway tracks.)

1. A steel for a rail, characterized in that: the steel plate comprises the following chemical components in percentage by mass: c: 0.74-0.86%, Si: 1.1-1.4%, P is less than or equal to 0.025%, S is less than or equal to 0.025%, Mn: 0.8 to 1.2%, Cu: 0.5-0.7%, and the balance of Fe and inevitable impurity elements.

2. The steel for a steel rail according to claim 1, wherein: the thickness of the steel plate is 200-230 mm, and the tissue type of the steel plate is as follows: tempered martensite + ferrite.

3. A method for producing the steel for steel rails according to claim 1, characterized in that: comprises the working procedures of heating, rolling and heat treatment, wherein the heat treatment adopts a tempering mode.

4. The method for producing a steel for steel rails according to claim 3, wherein: the heating procedure comprises the following steps: the steel billet is placed in a soaking pit after being demoulded for 10 hours, the temperature of the soaking pit is 500-.

5. The method for producing a steel for steel rails according to claim 3, wherein: the rolling procedure adopts a hot rolling mode.

6. The method for producing a steel for steel rails according to claim 3, wherein: the tempering medium in the heat treatment process is a mixture of water and kerosene, wherein the kerosene accounts for 55-65% of the mixture by weight.

7. The method for producing a steel for steel rails according to claim 3, wherein: the tempering temperature of the steel plate in the heat treatment process is as follows: keeping the temperature at 580 ℃ for 3-4.5min/mm at 550 ℃, and putting the tempered steel plate into an oil groove for oil cooling.

Technical Field

The invention relates to steel for a steel rail and a production method thereof.

Background

The steel plate industry for the track in China is rapidly developed, the total output is obviously increased, the steel plate is not only used in the field of the track for the vehicle, but also used in a mold, the total output of the production is second to the United states, the steel plate has leaped the second place in the world, and the steel plate becomes a genuine large mold country. The achievement can be mainly derived from the wide market which is unique in China and the advantages of relatively low resources and labor force, the great advantage is occupied in the international die casting trade market with very obvious cost performance, and the development prospect of the die casting industry in China is very wide in the future according to the situation.

The rail steel is classified into light rail, heavy rail, and crane rail according to its purpose, and the railway steel rail is a heavy rail. The weight of the heavy rail is between 38kg/m and 75kg/m, and the heavy rail is mainly used for laying rails for railway trunks, special lines, curves and tunnels, is specially used for large-scale projects, wharfs for loading containers and the like, and is specially used for gantry cranes. The supply and demand of steel for the railway in the next year greatly rises along with the rise of railway investment, and the railway investment in 2016 and 2020 is steadily promoted. In recent years, the Chinese and western parts are still intensively constructed, the eastern region continues to complete the residual project of planning, and the total completion mileage of intercity railways is expected to reach more than 1.7 kilometers and need more than 3 trillions of capital by the end of 2020. The high-speed rail export pace is accelerated, the global demand is greatly increased, the total mileage of the world high-speed railway is expected to exceed 5 kilometers by 2025 years according to the development planning of high-speed rails of various countries, the demand of rail steel is over 1000 million tons, the high-speed rail project connecting Malaysia and Singapore is expected to start to be called in the next year, and the total length of the high-speed rail planned to be built by countries such as India, Thailand and the like is up to 1 kilometer. The plan of China is that the highway network of China in China and China in China will connect Wumuqi in China with Kazakhstan, Uzbekistan, Tukumamstan and other countries in China, 17 countries are expected to be covered, the mileage is close to 5000 kilometers, and the global demand in the future is high.

The problems exist at present: technically, the production process level is improved, the yield of the hundred-meter steel rail is increased, and the technology of the ultra-long seamless line is perfected; improve the strength and the wear resistance of the material and prolong the service life of the steel rail. The invention provides steel for a steel rail and a production method thereof, and the steel has high technical content and high development difficulty, is the first time in domestic production, has the effect of realizing localization by virtue of production jacking and has good market prospect. The steel is mainly characterized in that: (1) the thickness of the steel plate is large and reaches 230mm specification; (2) the strength grade is high and reaches over 900MPa grade, so that the wear resistance of the steel is ensured; (3) the process design without Cr, Ni and Mo reduces the production cost. (4) The optimized heat treatment system ensures that the steel plate has certain toughness index.

Disclosure of Invention

In view of the above problems, an object of the present invention is to provide a steel for a rail, which steel has a tensile strength Rm of 900MPa or more and A₅₀More than or equal to 9 percent, normal temperature impact toughness of more than 30J, hardness HB of less than or equal to 300, maximum thickness of 230mm and low production cost.

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

the steel for the steel rail comprises the following chemical components in percentage by mass: c: 0.74-0.86%, Si: 1.1-1.4%, P is less than or equal to 0.025%, S is less than or equal to 0.025%, Mn: 0.8 to 1.2%, Cu: 0.5-0.7%, and the balance of Fe and inevitable impurity elements.

The steel for the steel rail has the thickness of 200-230 mm, and the steel plate structure type is as follows: tempered martensite + ferrite.

The invention also provides a production method of the steel for the steel rail, which comprises the working procedures of heating, rolling and heat treatment, wherein the heat treatment adopts a high-temperature tempering mode.

The invention relates to a production method of steel for steel rails, wherein a steel plate is produced by adopting a die casting process.

The invention relates to a production method of steel for steel rails, which comprises the following heating procedures: the steel billet is placed in a soaking pit after being demoulded for 10 hours, the temperature of the soaking pit is 500-.

The invention relates to a production method of steel for steel rails, wherein a hot rolling mode is adopted in a rolling procedure.

The invention relates to a production method of steel for steel rails, wherein a tempering medium is a mixture of water and kerosene, the weight ratio of the kerosene in the mixture is 55-65%, and the tempering temperature of a steel plate is as follows: keeping the temperature at 580 ℃ for 3-4.5min/mm at 550 ℃, and putting the tempered steel plate into an oil groove for oil cooling.

The steel plate provided by the invention has good mechanical property and processability and excellent die casting property, and meets the requirements of track steel, die casting molds, high-hardness large molds, mold frames and the like.

The steel for the steel rail provided by the invention has the following effects of various chemical components:

c: the C has the function of solid solution strengthening in the steel, so that the hardness of the wear-resistant steel is increased, and the wear resistance is improved. For large thickness rail steels, strength and wear resistance are key indicators, so the carbon content is designed as: 0.74-0.86%.

Si: si can reduce the austenite phase circle and increase the quenching temperature of the steel. Si can reduce the diffusion speed of carbon in ferrite, so that carbides separated out during tempering are not easy to aggregate, the tempering stability of the steel is improved, the steel with higher Si content can obviously reduce the tempering brittleness, the steel can be tempered at lower temperature, the internal stress in the steel can be reduced, and the steel plate has higher hardness. Si can reduce the oxidation effect during friction heating, improve the cold deformation hardening rate and the wear resistance of the steel, and the wear resistance of the silicon-manganese steel is improved along with the increase of the Si content. In addition, Si has a stronger affinity for oxygen than iron, and tends to produce low-melting-point silicates during welding, which increases the fluidity of slag and molten metal, and affects the weld quality. Therefore, considering the influence of Si on the hardenability, strength, tempering stability, wear resistance and welding of steel comprehensively, the Si content is preferably in the range of 1.1 to 1.4%.

Mn: mn expands the austenite phase region of the iron-carbon equilibrium phase ring, and its ability to stabilize the austenite structure is second only to Ni. Mn can significantly increase the hardenability of steel, and reduce the martensitic transformation temperature and critical cooling rate of steel. Mn and Fe can form a solid solution, increasing the hardness and strength of ferrite and austenite. Therefore, the addition of Mn increases the hardness and wear resistance of the steel, but if the Mn content is too high, it increases the temper brittleness of the steel. For the temper-treated wear-resistant steel sheet, on one hand, the Mn content needs to be increased to increase the hardness of the steel sheet, and on the other hand, the Mn content needs to be controlled to reduce the temper brittleness of the steel sheet. The preferable range of Mn content is 0.8-1.2%.

Cu: cu can improve the fatigue strength and the atmospheric corrosion resistance of the steel. Through solid solution and aging treatment, the precipitation strengthening effect can be achieved, the strength, the wear resistance and the yield ratio of the steel are obviously improved, and the weldability of the steel is not adversely affected. The Cu content is preferably 0.5 to 0.7%.

P, S is a harmful element, and its content is reduced as much as possible.

The invention adopts the design of chemical components with lower alloy content, and Cr, Ni, Mo and the like are not added, so that the production cost is greatly reduced; by optimizing the heat treatment mode, each mechanical property index of the obtained steel plate is excellent, and the obtained steel plate has a finer tissue structure and better processing type.

The mechanical properties of the steel plate provided by the invention are as follows: the tensile strength Rm of the steel plate is more than or equal to 900MPa and A₅₀More than or equal to 9 percent, normal temperature impact toughness of more than 30J, hardness HB of less than or equal to 300 and maximum thickness of 230 mm.

Drawings

FIG. 1 structural diagram (500X) of the steel sheet of example 1.

FIG. 2 structural diagram (500X) of the steel sheet of example 2.

FIG. 3 structural diagram (500X) of the steel sheet of example 3.

FIG. 4 structural diagram (500X) of the steel sheet of example 4.

FIG. 5 structural diagram (500X) of the steel sheet of example 5.

FIG. 6 structural diagram (500X) of the steel sheet of example 6.

Detailed Description