阅读说明：本技术 一种高强度铸钢及其制备方法 (High-strength cast steel and preparation method thereof ) 是由 高文通 于 2019-09-18 设计创作，主要内容包括：本发明涉及铸钢领域,具体涉及一种高强度铸钢及其制备方法。本发明公开一种高强度铸钢,其特征在于,以质量百分比计,该高强度铸钢由以下成分组成：C：0.24％～0.3％,Si：1％～2％,Mn：1.8％～3％,Cr：0.3％～0.7％,Mo：0.2％～0.4％,Ti：0.01％～0.04％,Al：0.01％～0.08％,B：0.001％～0.008％,稀土元素RE：0.01％～0.06％,S≤0.03％,P≤0.03％,余量为Fe。本发明解决了目前铸钢市场上低合金高强度铸钢虽然强度高、硬度高,但是普遍存在韧性较低的问题。本发明所制备的高强度铸钢兼具高强度、高硬度和高韧性三种优点,可满足市场需求,具有较高的应用价值。(The invention relates to the field of cast steel, in particular to high-strength cast steel and a preparation method thereof. The invention discloses high-strength cast steel which is characterized by comprising the following components in percentage by mass: c: 0.24% -0.3%, Si: 1% -2%, Mn: 1.8% -3%, Cr: 0.3% -0.7%, Mo: 0.2-0.4%, Ti: 0.01-0.04%, Al: 0.01% -0.08%, B: 0.001% -0.008%, rare earth element RE: 0.01 to 0.06 percent of the total weight of the alloy, less than or equal to 0.03 percent of S, less than or equal to 0.03 percent of P and the balance of Fe. The invention solves the problem that the low-alloy high-strength cast steel in the current cast steel market generally has lower toughness although the low-alloy high-strength cast steel has high strength and high hardness. The high-strength cast steel prepared by the invention has the advantages of high strength, high hardness and high toughness, can meet market demands, and has high application value.)

1. The high-strength cast steel is characterized by comprising the following components in percentage by mass:

c: 0.24% -0.3%, Si: 1% -2%, Mn: 1.8% -3%, Cr: 0.3% -0.7%, Mo: 0.2-0.4%, Ti: 0.01-0.04%, Al: 0.01% -0.08%, B: 0.001% -0.008%, rare earth element RE: 0.01 to 0.06 percent of S, less than or equal to 0.01 percent of P, and the balance of Fe;

the rare earth element RE is one or more of cerium, lanthanum and yttrium.

2. The high-strength cast steel according to claim 1, characterized in that it consists of, in mass%:

c: 0.26-0.3%, Si: 1.5% -1.8%, Mn: 1.8-2.4%, Cr: 0.3% -0.5%, Mo: 0.2-0.4%, Ti: 0.02% -0.03%, Al: 0.02% -0.05%, B: 0.003-0.005%, rare earth element RE: 0.02-0.03%, S is less than or equal to 0.01%, P is less than or equal to 0.01%, and the balance is Fe;

the rare earth element RE is one of cerium, lanthanum and yttrium.

3. A method for producing a high-strength cast steel according to claim 1 or 2, characterized by comprising the steps of:

s1, putting raw materials into a blast furnace according to composition components to be smelted into molten steel, and desulfurizing by adopting a mechanical stirring method to obtain pretreated molten steel; s in the pretreated molten steel is less than or equal to 0.01 percent;

s2, adding the pretreated molten steel into a converter, carrying out top-bottom combined blowing, dephosphorizing in the blowing, and desulfurizing again to ensure that S is less than or equal to 0.005% and P is less than or equal to 0.005%; at the later stage of blowing, adding a deoxidant for deoxidization; after blowing is finished, adding hepta-aluminum dodecacalcium to ensure that the alkalinity of the slag is more than 5.2; simultaneously, adding alloy for fine adjustment according to the component content of the molten steel, thereby carrying out steel tapping alloying and obtaining high-strength cast molten steel;

the deoxidant is formed by compounding Al and SiC; al in the oxygen scavenger: the mass ratio of SiC is 1: 2-5;

s3, treating the high-strength cast steel liquid by adopting a vacuum circulating degassing method, and discharging the high-strength cast steel liquid when the temperature of the high-strength cast steel liquid is 1660-1700 ℃; and carrying out slagging-off and casting to obtain a casting, and carrying out heat treatment to obtain the high-strength cast steel.

4. The method for preparing a high-strength cast steel according to claim 3, wherein the alloy comprises one or more of metallic chromium, metallic manganese, metallic molybdenum and metallic titanium.

5. The method for manufacturing high-strength cast steel according to claim 3, wherein the casting temperature in step S3 is 1450-1520 ℃.

6. The method for manufacturing high-strength cast steel according to claim 3, wherein the heat treatment in step S3 is specifically:

a. heating the casting piece in an electric furnace at room temperature, heating to 1050-1100 ℃ at a speed of 60 ℃/h for austenitizing, keeping the temperature for 3-6 h, and air-cooling to room temperature;

b. repeating the step a once;

c. b, putting the casting piece after air cooling in the step b into an electric furnace again for heating, raising the temperature to 800-850 ℃ at a speed of 55 ℃/h, and then preserving the heat for 15-20 h; then, cooling at the speed of 30 ℃/h, opening the electric furnace when the temperature is reduced to 350-400 ℃, and cooling to room temperature;

d. carrying out first tempering: the temperature is 450-475 ℃, and the time is 3-5 h; carrying out secondary tempering: the temperature is 425-450 ℃, and the time is 10-12 h.

Technical Field

The invention relates to the field of cast steel, in particular to high-strength cast steel and a preparation method thereof.

Background

Steel is always an important support for national economic construction and social development. With the rapid development of economy in China, the demand of steel is increased rapidly year by year, and the yield is increased dramatically. From 1996 in China, the yield of crude steel is 1 hundred million tons, leaps the first in the world, to 2012 in China, the yield of crude steel in continents is 7.16 hundred million tons, which accounts for 46.3 percent of the global steel yield, and the yield of cast steel in China is doubled several times in several years, thereby providing strong assistance for highway, railway traffic, urban construction, national defense construction and the like in China. Although China is a big iron and steel country, China is not a strong iron and steel country, the capacity of common steel is surplus, and some high-performance steel still depends on imports. Therefore, the research and development of high-performance cast steel is one of the important ways to relieve the excess of the cast steel productivity in China and effectively improve the cast steel hard strength in China.

At present, low-alloy high-strength cast steel on the cast steel market generally has the problem of low toughness although the low-alloy high-strength cast steel has high strength and high hardness.

Disclosure of Invention

In order to solve the problems, the invention provides high-strength cast steel which comprises the following components in percentage by mass:

c: 0.24% -0.3%, Si: 1% -2%, Mn: 1.8% -3%, Cr: 0.3% -0.7%, Mo: 0.2-0.4%, Ti: 0.01-0.04%, Al: 0.01% -0.08%, B: 0.003-0.005%, rare earth element RE: 0.02-0.03%, S is less than or equal to 0.01%, P is less than or equal to 0.01%, and the balance is Fe;

the rare earth element RE is one or more of cerium, lanthanum and yttrium.

Preferably, the high-strength cast steel consists of the following components in percentage by mass:

c: 0.26-0.3%, Si: 1.5% -1.8%, Mn: 1.8-2.4%, Cr: 0.3% -0.5%, Mo: 0.2-0.4%, Ti: 0.02% -0.03%, Al: 0.02% -0.05%, B: 0.003-0.005%, rare earth element RE: 0.02-0.03%, S is less than or equal to 0.01%, P is less than or equal to 0.01%, and the balance is Fe;

the rare earth element RE is one of cerium, lanthanum and yttrium.

The invention also aims to provide a preparation method of the high-strength cast steel, which comprises the following specific steps:

s1, putting raw materials into a blast furnace according to composition components to be smelted into molten steel, and desulfurizing by adopting a mechanical stirring method to obtain pretreated molten steel; s in the pretreated molten steel is less than or equal to 0.01 percent;

s2, adding the pretreated molten steel into a converter, carrying out top-bottom combined blowing, dephosphorizing in the blowing, and desulfurizing again to ensure that S is less than or equal to 0.005% and P is less than or equal to 0.005%; in the later stage of blowing, deoxidizing by adding a deoxidant; after blowing is finished, adding hepta-aluminum dodecacalcium to ensure that the alkalinity of the slag is more than 5.2; simultaneously, adding alloy for fine adjustment according to the component content of the molten steel, thereby carrying out steel tapping alloying and obtaining high-strength cast molten steel;

the deoxidant is formed by compounding Al and SiC; al in the oxygen scavenger: the mass ratio of SiC is 1: 2-5;

s3, treating the high-strength cast steel liquid by adopting a vacuum circulating degassing method, and discharging the high-strength cast steel liquid when the temperature of the high-strength cast steel liquid is 1660-1700 ℃; and carrying out slagging-off and casting to obtain a casting, and carrying out heat treatment to obtain the high-strength cast steel.

Preferably, the alloy comprises one or more of metallic chromium, metallic manganese, metallic molybdenum and metallic titanium.

Preferably, the casting temperature in the step S3 is 1450-1520 ℃.

Preferably, the heat treatment in step S3 is specifically:

a. heating the casting piece in an electric furnace at room temperature, heating to 1050-1100 ℃ at a speed of 60 ℃/h for austenitizing, keeping the temperature for 3-6 h, and air-cooling to room temperature;

b. repeating the step a once;

c. b, putting the casting piece after air cooling in the step b into an electric furnace again for heating, raising the temperature to 800-850 ℃ at a speed of 55 ℃/h, and then preserving the heat for 15-20 h; then, cooling at the speed of 30 ℃/h, opening the electric furnace when the temperature is reduced to 350-400 ℃, and cooling to room temperature;

d. carrying out first tempering: the temperature is 450-475 ℃, and the time is 3-5 h; carrying out secondary tempering: the temperature is 425-450 ℃, and the time is 10-12 h.

The invention has the beneficial effects that:

1. the invention controls the dosage of Cr at 0.3% -0.7%, which obviously improves the strength, hardness, hardenability and wear resistance of the steel and simultaneously improves the oxidation resistance and corrosion resistance of the steel; the added Mo mainly increases the secondary hardening effect, the 0.2-0.4% can ensure that the steel keeps higher hardness under different solid solution treatment conditions, the precipitated phase plays a role in strengthening in the aging process, and simultaneously the steel has good mother-of-pear property, and the Mo also can improve the seawater corrosion resistance of the stainless steel. A small amount of B element is added into a steel material for manufacturing cast steel parts, so that the mechanical property of the cast steel parts is greatly improved, and the addition of B is 0.003-0.005% so that the cast steel has higher tensile strength and yield strength and higher impact power and hardness, the cast steel parts show good working performance and service life in a nuclear power unit, and the maintenance cost is greatly reduced; meanwhile, a small amount of Ti is added, so that the cast steel parts have higher elongation and section shrinkage, and the use safety of the cast steel parts is ensured.

2. According to the invention, a compound of Al and SiC is added during blowing to serve as an oxygen scavenger, Al and SiC can play a role in diffusion deoxidation after being mixed according to a certain proportion, and meanwhile, the added rare earth element RE can continuously play a role in deep deoxidation after Al and SiC are added for deoxidation. Meanwhile, the trace rare earth element RE also reduces the mass fraction of sulfur in the steel to be less than 0.0015 percent.

3. The processes of temperature change, bottom blowing control, inclusion removal mechanism change and the like in the processes from tapping to vacuum circulating degassing are linked with the selection of the refining slag, and the change of the physical and chemical properties of the refining slag is matched with the change of the molten steel refining process, so that the refining slag can keep good melting property, certain desulfurization capability and good inclusion adsorption capability in the late tapping period to the end of circulating degassing, the effects of better removing and controlling brittle nonmetallic inclusions in cast steel can be achieved, and the problems of low-temperature tapping and excessive-temperature tapping of low-phosphorus molten steel smelted by a converter and the like are solved simultaneouslyDifficult slag melting and long refining time. The low-melting-point refining slag mainly containing heptaaluminum and dodecacalcium is added to facilitate slag system melting and rapid slagging, and the high-alkalinity slag is beneficial to molten steel desulfurization and molten steel Al₂O₃The adsorption of the inclusions achieves the purpose of refining the molten steel earlier.

4. The heat treatment mode of the invention is that the casting is firstly subjected to austenite homogenization heating; after austenitizing in an electric furnace, air cooling is carried out, and then annealing treatment is carried out on the casting piece after the same austenitizing and air cooling processes are carried out, so that the obtained product structure is more uniform, and the toughness of the low-alloy high-strength cast steel is further improved. Then, tempering twice, wherein the sample after the first tempering has higher dislocation density, and dislocations are intertwined with each other and arranged in disorder; after the second tempering, the dislocation is dynamically recovered, and the dislocation density is reduced along with the first tempering. The decrease in dislocation density results in a decrease in the interaction between dislocations and an increase in the ability of dislocations to move. In addition, the dislocation motion can reduce the propagation of cracks and plays a certain role in improving the plasticity and toughness of the material. The cast steel prepared by the invention has the tensile strength of 1585MPa, the hardness of 41.4HRC and the elongation of 10.4%.

5. The high-strength cast steel prepared by the invention has the advantages of high strength, high hardness and high toughness, can meet market demands, and has high application value.

Detailed Description

For the sake of understanding, the present invention will be described in detail below with reference to specific examples. It is specifically intended that the present embodiments be considered as illustrative only, and that various modifications and changes in light thereof will be suggested to persons skilled in the art and are to be included within the scope of the present invention.