阅读说明：本技术 合金铸钢、其制作方法及应用 (Alloy cast steel, and manufacturing method and application thereof ) 是由 文超 张俊新 高红梅 孙轶山 吴童童 于 2018-05-16 设计创作，主要内容包括：本发明提供了一种合金铸钢、其制作方法及应用。以重量百分比计,该合金铸钢包括：碳0.12％～0.21％、硅0.15％～0.35％、锰1.21％～1.50％、磷≤0.035％、硫≤0.035％、铬≤0.25％、钼0.31％～0.56％、铝0.02％～0.04％、铌0.02％～0.04％,氮≤0.020％,余量为铁及其他不可避免的元素。具有上述组成的铸钢材料形成的铸钢,由于具有合适的碳、锰、钼和铬的含量,因此提高了铸钢的强度；同时通过控制其他元素在合适的含量与其进行配合,进而在不采用镍的前体下,不仅提高了铸钢强度而且提高了其低温韧性。(The invention provides alloy cast steel, a manufacturing method and application thereof. The alloy cast steel comprises the following components in percentage by weight: 0.12 to 0.21 percent of carbon, 0.15 to 0.35 percent of silicon, 1.21 to 1.50 percent of manganese, less than or equal to 0.035 percent of phosphorus, less than or equal to 0.035 percent of sulfur, less than or equal to 0.25 percent of chromium, 0.31 to 0.56 percent of molybdenum, 0.02 to 0.04 percent of aluminum, 0.02 to 0.04 percent of niobium, less than or equal to 0.020 percent of nitrogen, and the balance of iron and other inevitable elements. Cast steel formed of the cast steel material having the above composition has improved strength of cast steel due to appropriate contents of carbon, manganese, molybdenum and chromium; meanwhile, other elements are controlled to be matched with the nickel-based alloy at proper content, so that the strength of the cast steel is improved and the low-temperature toughness of the cast steel is improved without adopting a nickel precursor.)

1. An alloy cast steel, characterized in that it comprises, in weight percent:

0.12 to 0.21 percent of carbon, 0.15 to 0.35 percent of silicon, 1.21 to 1.50 percent of manganese, less than or equal to 0.035 percent of phosphorus, less than or equal to 0.035 percent of sulfur, less than or equal to 0.25 percent of chromium, 0.31 to 0.56 percent of molybdenum, 0.02 to 0.04 percent of aluminum, 0.02 to 0.04 percent of niobium, less than or equal to 0.020 percent of nitrogen, and the balance of iron and other inevitable elements.

2. Alloy cast steel according to claim 1, characterized in that the carbon content is preferably 0.14% to 0.19%, the manganese content is preferably 1.36% to 1.50%, and the molybdenum content is preferably 0.31% to 0.45% in weight percent.

3. The alloy cast steel according to claim 1, wherein the contents of nitrogen, aluminum and niobium in the alloy cast steel satisfy 0. ltoreq. aluminum +0.26 xniobium-2.5 xN. ltoreq.0.010%.

4. The alloy cast steel according to claim 1, characterized in that the weight percentage of phosphorus is less than or equal to 0.020% and the weight percentage of sulfur is less than or equal to 0.015%.

5. The alloy cast steel according to claim 1, wherein the tensile strength Q value of the alloy cast steel is calculated as Q200 × carbon +25 × manganese +16 × molybdenum +3 × chromium-63, and Q value is not less than 0.

6. Alloy cast steel according to claim 1, characterized in that the carbon equivalent is calculated according to the following calculation formula CE ═ C + (Mn + Si)/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15, the calculated carbon equivalent being not more than 0.60%, preferably the calculated carbon equivalent being not more than 0.55%.

7. The alloy cast steel according to any one of claims 1 to 6, characterized in that the tensile strength of the alloy cast steel is not less than 725MPa, preferably the yield strength of the alloy cast steel is not less than 585 MPa; the elongation of the alloy cast steel is preferably more than or equal to 17 percent, and the reduction of area of the alloy cast steel is preferably more than or equal to 35 percent; the Charpy V-shaped impact energy of the alloy cast steel at-40 ℃ is preferably more than or equal to 40J, the Charpy V-shaped impact energy of the alloy cast steel at-50 ℃ is preferably more than or equal to 27J, and the Charpy V-shaped impact energy of the alloy cast steel at-60 ℃ is preferably more than or equal to 27J; the hardness of the alloy cast steel is preferably in the range of 211HBW to 285 HBW.

8. A method of manufacturing the alloy cast steel according to any one of claims 1 to 7, characterized in that it comprises:

carrying out smelting, casting and molding on the cast steel material to obtain a steel casting;

and carrying out heat treatment on the steel casting to obtain cast steel, wherein the heat treatment comprises the steps of sequentially carrying out high-temperature normalizing treatment, quenching treatment and tempering treatment on the steel casting.

9. The manufacturing method of claim 8, wherein the high-temperature normalizing treatment comprises heating the steel casting to 951-1050 ℃ and keeping the temperature for 2-6 hours, discharging the steel casting out of a furnace, and air-cooling the steel casting to room temperature.

10. The manufacturing method according to claim 8, wherein the quenching treatment comprises heating the steel casting after the high-temperature normalizing treatment to 930-950 ℃, preserving the heat for 2-5 hours, then discharging and cooling, wherein the cooling speed in the quenching treatment is controlled to be 10.1-100 ℃/s, and preferably, the cooling medium used in the cooling is an aqueous solution containing 5-15% of sodium chloride or water.

11. The manufacturing method of claim 8, wherein the tempering treatment comprises heating the quenched steel casting to 630-680 ℃, keeping the temperature for 2-7 hours, discharging the steel casting out of a furnace, and cooling the steel casting to room temperature, wherein the cooling in the tempering treatment is performed in air, oil, water or a water-soluble medium.

12. The method of claim 8, wherein the tempering results in a predominantly tempered sorbite metallographic structure.

13. A railway component formed by molding the alloy cast steel according to any one of claims 1 to 7.

14. The railway component of claim 13, wherein the railway component is a coupler socket, coupler, clamp, brake disc, axle housing, gearbox, yoke, bogie, frame, spider, axle or support axle.

Technical Field

The invention relates to the field of metal smelting, in particular to alloy cast steel, and a manufacturing method and application thereof.

Background

With the continuous increase of national economy and the continuous expansion of market demand, the whole wagon and related parts of the railway wagon in China rapidly enter high and cold regions such as Russia, and therefore steel castings used by the wagon are required to have good low-temperature performance. As shown in Table 1, typical AAR M201-2015 grade D steel and ASTM A487 4B mechanical property requirements.

TABLE 1 mechanical Property requirements for grade D steels of AAR M201-2015 and 4B in ASTM A487

In general, suitable cast steel compositions have been sought to meet the above-described property spectrum, and to minimize the use of low weld carbon equivalent and improve low temperature impact toughness. For example, patent CN103436807B proposes a new cast steel composition with a carbon equivalent of 0.52-0.58% (the formula for calculating carbon equivalent is C + Mn/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15) on the premise of achieving the above mechanical performance index. Vanadium and niobium are added to compound refined grains, and chromium, nickel and molybdenum are used for improving hardenability and strength. However, with the widespread use of nickel in the fields of stainless steel and heat-resistant steel, nickel resources are becoming scarce. Therefore, how to reduce nickel or not use nickel to achieve equivalent performance becomes a major research point. Secondly, the addition of nickel can improve the low-temperature toughness, and if nickel is not adopted, how to ensure or improve the low-temperature impact toughness is difficult to study. In addition, in order to achieve the mechanical properties of table 1 in the railway wagon, the formula of the carbon equivalent is CE ═ C + (Mn + Si)/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15, and how to ensure the strength without increasing the carbon equivalent under the new formula of the carbon equivalent is another difficulty.

Disclosure of Invention

The invention mainly aims to provide alloy cast steel, a manufacturing method and application thereof, and aims to solve the problem that the high strength and high and low temperature toughness of cast steel without nickel in the prior art are difficult to ensure.

In order to achieve the above object, according to one aspect of the present invention, there is provided an alloy cast steel including, in weight percent: 0.12 to 0.21 percent of carbon, 0.15 to 0.35 percent of silicon, 1.21 to 1.50 percent of manganese, less than or equal to 0.035 percent of phosphorus, less than or equal to 0.035 percent of sulfur, less than or equal to 0.25 percent of chromium, 0.31 to 0.56 percent of molybdenum, 0.02 to 0.04 percent of aluminum, 0.02 to 0.04 percent of niobium, less than or equal to 0.020 percent of nitrogen, and the balance of iron and other inevitable elements.

Further, the content of carbon is preferably 0.14 to 0.19 percent, the content of manganese is preferably 1.36 to 1.50 percent, and the content of molybdenum is preferably 0.31 to 0.45 percent in percentage by weight.

Furthermore, in the alloy cast steel, the content of nitrogen, aluminum and niobium is more than or equal to 0 and less than or equal to aluminum plus 0.26 multiplied by niobium minus 2.5 multiplied by N and less than or equal to 0.010 percent.

Furthermore, the weight percentage of the phosphorus is less than or equal to 0.020 percent, and the weight percentage of the sulfur is less than or equal to 0.015 percent.

Further, the tensile strength Q value of the alloy cast steel is calculated according to Q being 200 × carbon +25 × manganese +16 × molybdenum +3 × chromium-63, and the Q value is not less than 0.

Further, the carbon equivalent is calculated according to the following calculation formula CE ═ C + (Mn + Si)/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15, and the calculated carbon equivalent is not more than 0.60%, preferably not more than 0.55%.

Furthermore, the tensile strength of the alloy cast steel is more than or equal to 725MPa, and the yield strength of the alloy cast steel is preferably more than or equal to 585 MPa; the elongation of the alloy cast steel is preferably more than or equal to 17 percent, and the reduction of area of the alloy cast steel is preferably more than or equal to 35 percent; preferably, the Charpy V-shaped impact energy of the alloy cast steel at-40 ℃ is more than or equal to 40J, the Charpy V-shaped impact energy of the alloy cast steel at-50 ℃ is more than or equal to 27J, and the Charpy V-shaped impact energy of the alloy cast steel at-60 ℃ is more than or equal to 27J; the hardness of the alloy cast steel is preferably in the range of 211HBW to 285 HBW.

According to another aspect of the present invention, there is provided a method of manufacturing an alloy cast steel according to any one of the above, the method comprising: carrying out smelting, casting and molding on the cast steel material to obtain a steel casting; and carrying out heat treatment on the steel casting to obtain the cast steel, wherein the heat treatment comprises the steps of sequentially carrying out high-temperature normalizing treatment, quenching treatment and tempering treatment on the steel casting.

Further, the high-temperature normalizing treatment comprises heating the steel casting to 951-1050 ℃, preserving heat for 2-6 hours, discharging the steel casting out of the furnace, and air cooling the steel casting to room temperature.

Further, the quenching treatment comprises heating the steel casting after the high-temperature normalizing treatment to 930-950 ℃ and preserving the heat for 2-5 hours, then discharging and cooling, wherein the cooling speed in the quenching treatment is controlled to be 10.1-100 ℃/s, and preferably, the cooling medium adopted in the cooling is 5-15% of sodium chloride aqueous solution or water.

Further, the tempering treatment comprises heating the quenched steel casting to 630-680 ℃, preserving heat for 2-7 hours, discharging and cooling to room temperature, wherein the cooling in the tempering treatment is carried out in air, oil, water or a water-soluble medium.

Further, the above tempering treatment gives a metallographic structure mainly of tempered sorbite.

According to still another aspect of the present invention, there is provided a railway component molded from the alloy cast steel of any one of the above.

Further, the railway parts are a coupler seat, a coupler, a clamp, a brake disc, an axle box body, a gear box, a coupler yoke, a bogie, a framework, a star plate, an axle or a support axle.

By applying the technical scheme of the invention, the cast steel formed by the cast steel material with the composition has proper contents of carbon, manganese, molybdenum and chromium, so that the strength of the cast steel is improved; meanwhile, other elements are controlled to be matched with the nickel-based alloy at proper content, so that the strength of the cast steel is improved and the low-temperature toughness of the cast steel is improved without adopting a nickel precursor.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a picture of a metallographic structure of the cast steel of example 1 of the present application, after being subjected to high-temperature normalizing treatment + quenching tempering treatment, magnified by 100 times;

fig. 2 is a picture of a metallographic structure of the cast steel of example 1 of the present application after high-temperature normalizing treatment plus quenching and tempering treatment magnified 500 times.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

As analyzed by the background of the present application, in order to meet the strength requirements in prior art cast steels, nickel is generally used; if the high strength and the high and low temperature toughness of the cast steel are difficult to ensure without adopting the cast steel composition formula of the prior nickel, the application provides an alloy cast steel, a manufacturing method and application thereof in order to solve the problem.

In an exemplary embodiment of the present application, there is provided an alloy cast steel including, in weight percent: 0.12 to 0.21 percent of carbon, 0.15 to 0.35 percent of silicon, 1.21 to 1.50 percent of manganese, less than or equal to 0.035 percent of phosphorus, less than or equal to 0.035 percent of sulfur, less than or equal to 0.25 percent of chromium, 0.31 to 0.56 percent of molybdenum, 0.02 to 0.04 percent of aluminum, 0.02 to 0.04 percent of niobium, less than or equal to 0.020 percent of nitrogen, and the balance of iron and other inevitable elements. The aforementioned unavoidable elements do not contain nickel elements, i.e. the alloy cast steel of the present application does not contain nickel elements.

Carbon: the main function of carbon is as an interstitial solid solution element to improve the strength of cast steel. However, too high carbon may reduce plasticity, toughness, and especially plasticity; and too low carbon requires additional strength elements such as manganese and molybdenum. From the matching point of performance and cost, the carbon content is controlled to be 0.12-0.21%, and preferably 0.13-0.21%. In order to ensure the matching of strength, plasticity and toughness, the content of carbon is preferably controlled to be 0.14-0.19% (the content and the content of each element described below are weight contents).

Silicon: the silicon is mainly used as a reducing agent and a deoxidizing agent in the steel-making process. However, too high silicon may cause solid solution strengthening of austenite and ferrite, resulting in a decrease in toughness, and in order to meet the requirements in table 1, the content of silicon is controlled to be 0.15% to 0.35% manganese: manganese is an effective element for improving the strength of the alloy cast steel, and can effectively improve the low-temperature impact toughness of the cast steel and also improve the low-temperature toughness of a welding seam. In addition, in the present application, the addition of manganese promotes the solubility of nitrogen in steel, and facilitates the complex addition of aluminum and niobium to form aluminum nitride, niobium carbonitride, and the like. However, when the manganese exceeds 1.5%, chemical composition segregation during casting is increased to cause reduction in plasticity and toughness, but too low manganese causes insufficient strength. Therefore, the content of manganese is controlled to be 1.21-1.50%. In order to reasonably control the material cost, the manganese content can be further optimized to be 1.36-1.50%.

Phosphorus and sulfur: in the alloy cast steel, phosphorus and sulfur are harmful elements, which affect the purity of the steel, and too high phosphorus and sulfur can reduce impact toughness, especially low-temperature toughness. But if the control is too low, the production cost is increased greatly, and the contents of phosphorus and sulfur are controlled to be less than or equal to 0.035 percent and less than or equal to 0.035 percent by combining the factors. In order to further improve the impact toughness, especially the low-temperature impact toughness, the controlled contents of phosphorus and sulfur are further optimized to be less than or equal to 0.020% of phosphorus and less than or equal to 0.015% of sulfur.

Molybdenum: manganese is an effective element for improving the strength of the alloy cast steel, and molybdenum is a key element for improving the plasticity. However, too high molybdenum reduces toughness and too low does not guarantee the ability of the steel casting to obtain tempered sorbite. Therefore, the content of the molybdenum is controlled to be 0.31-0.56%. In order to reasonably control the material cost, the content of molybdenum can be further optimized to be 0.31-0.45%.

Chromium: chromium is an effective element for improving the strength of the alloy cast steel, and the hardenability and the strength of the steel are further enhanced by the combined action of chromium, manganese and molybdenum. Too high chromium addition results in an increase in carbon equivalent, while too low chromium may not achieve suitable strength. Therefore, the content of chromium is controlled to be less than or equal to 0.25 percent, and preferably 0.08 to 0.25 percent.

Aluminum and niobium cooperate to refine grains, particularly austenite grains, and nitrogen is primarily responsible for aluminum and niobium to form a certain amount of nitrides that may promote grain refinement of cast steel during casting and high temperature normalizing. In addition, aluminum can be used as an effective deoxidizer. However, the excessively high aluminum content increases the defects and cracking tendency of non-metallic inclusions, and the excessively low aluminum content does not refine grains, so that the aluminum content is controlled to be 0.02 to 0.04 percent. The addition of niobium also reduces the presence of mixed austenite grains, but too high niobium severely reduces the low temperature impact toughness, while too low niobium does not complex with aluminum. Therefore, the content of niobium is controlled to be 0.02-0.04%. In order to form a proper amount of nitride, nitrogen is controlled to be 0.020% or less, and more preferably, 0.26 Xniobium-2.5 XN is 0.010% or less.

In summary, cast steels formed of cast steel materials having the above composition have improved strength of cast steels due to appropriate contents of carbon, manganese, molybdenum and chromium; meanwhile, other elements are controlled to be matched with the nickel-based alloy at proper content, so that the strength of the cast steel is improved and the low-temperature toughness of the cast steel is improved without adopting a nickel precursor.

Preferably, the tensile strength Q value of a cast steel formed from the cast steel material is determined in terms of Q ═ 200 × carbon +25 × manganese +16 × molybdenum +3 × chromium-63: q is the ability to rapidly judge the strength obtained by the present invention, Q is not less than 0, and the Q value is preferably 5 or more in order to ensure better strength. Through the guidance of the formula, whether the smelted components meet the strength requirement or not is fed back when the on-site batching is convenient. Further adjustments to the composition can be made by this formula.

In addition, the carbon equivalent formula is an important index for measuring the welding performance of the material at present. According to the index, the welding performance of the material can be rapidly judged, and the material needs an approximate welding process in the following process. In order to improve the weldability, the carbon equivalent is preferably calculated according to the following calculation formula CE ═ C + (Mn + Si)/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15, and the calculated carbon equivalent is not more than 0.60%, and more preferably not more than 0.55%. The lower the carbon equivalent, the simpler the welding method chosen, the lower the preheating temperature (even without preheating), the lower the cost of the welding wire chosen, etc.

The tensile strength of the preferred alloy cast steel is more than or equal to 725MPa, and the yield strength of the preferred alloy cast steel is more than or equal to 585 MPa; the elongation of the alloy cast steel is preferably not less than 17%, and more preferably not less than 20%; the reduction of area of the preferred alloy cast steel is more than or equal to 35 percent; preferably, the Charpy V-shaped impact energy of the alloy cast steel at-40 ℃ is more than or equal to 40J, the Charpy V-shaped impact energy of the alloy cast steel at-50 ℃ is more than or equal to 27J, and the Charpy V-shaped impact energy of the alloy cast steel at-60 ℃ is more than or equal to 27J; the hardness of the alloy cast steel is preferably in the range of 211HBW to 285 HBW. It can be seen that the alloy cast steel of the present application fully meets the mechanical property requirements of grade D steel of AAR M201-2015 and 4B in ASTM a 487.

In another exemplary embodiment of the present application, there is provided a method for manufacturing an alloy cast steel, including: carrying out smelting, casting and molding on the cast steel material to obtain a steel casting; and carrying out heat treatment on the steel casting to obtain the cast steel, wherein the heat treatment comprises the steps of sequentially carrying out high-temperature normalizing treatment, quenching treatment and tempering treatment on the steel casting.

The cast steel raw material is subjected to smelting, casting and molding and then is subjected to heat treatment, and the obtained cast steel has proper contents of carbon, manganese, molybdenum and chromium, so that the strength of the cast steel is improved; meanwhile, other elements are controlled to be matched with the cast steel in proper content, so that the strength of the cast steel is improved and the low-temperature toughness of the cast steel is improved on the basis of not adopting nickel. And on the basis of ingredient improvement, the comprehensive mechanical property of the alloy cast steel is further improved through the heat treatment mode.

In order to fully exert the functions of the above elements, it is preferable to perform the smelting and casting molding of the cast steel material by an arc furnace smelting process or a medium frequency induction furnace smelting process.

The process of the electric arc furnace smelting process can refer to the prior art, and preferably is implemented by referring to the following processes:

1. the requirement of charging materials: in order to ensure that the trace harmful elements such As Sn, Sb and As are controlled in the range As low As possible, high-quality pig iron and large high-quality scrap steel are adopted As smelting furnace burden. The furnace burden can be various carbon steels, similar steels with similar components, pig iron meeting requirements, various related iron alloys, aluminum blocks and the like, turning materials and light and thin materials are extruded into blocks, and large materials and long materials are cut into proper blocks. Closed containers, explosives, non-ferrous metals and other harmful substances should not be charged into the furnace. All furnace charge added in the later stage of smelting must be subjected to heat preservation baking at the temperature of more than 450 ℃ for not less than 2 hours; other charged materials should also be kept dry.

2. Selecting furnace burden and loading operation: according to the technological requirements, the corresponding furnace charge is put into the electric arc furnace, and 5.0% -7.0% of lime is added to the front furnace bottom to ensure the earlier dephosphorization and protect the furnace bottom.

3. Melting furnace charge and slagging dephosphorization operation: and electrifying with the maximum allowable power to push materials for fluxing. The carbon melting and cleaning process should ensure that the decarbonization amount in the oxidation period is not less than 0.30 percent. After the melting is finished, carbon, manganese, phosphorus and other main elements required to be checked in the steel meet the specified requirements.

4. And (3) oxidation dephosphorization decarburization operation: the oxidation process is preferably carried out by comprehensive oxidation of ore and oxygen to ensure smooth dephosphorization, degassing and impurity removal. When the temperature of the molten pool reaches 1600 ℃, ferromanganese is added for pre-deoxidation, so that the manganese content of the molten pool is more than 0.90-1.1%. After the pre-deoxidation is finished, measuring the temperature, sampling and analyzing the carbon, the phosphorus and the manganeseAnd (4) content. When W is_C≥0.10％、W_P≥0.020％、W_MnMore than or equal to 0.20 percent, and when the temperature of the molten pool is not lower than the tapping temperature, the oxidized slag is allowed to be completely removed.

5. And (3) deoxidation and desulfurization operation in a reduction period: after the oxidizing slag is completely removed, 2-3% of dry thin slag material is rapidly added, and high-power is supplied to rapidly melt the dry slag and cover the molten steel so as to prevent the molten steel from breathing in and cooling. After the thin slag is formed, 0.50kg of pure aluminum/(t steel) is inserted into a molten pool for pre-deoxidation, and a certain amount of reducing agent (carbon powder, silicon carbide powder and the like) is uniformly sprayed and scattered on the surface of the molten slag; the hearth has better sealing property to promote the rapid formation of white slag. The holding time of the white slag in the molten pool is not less than 10 min.

6. Adjusting component tapping operation: sampling and analyzing all elements in the white slag state, adding related alloy when the elements are not qualified, adjusting the components, measuring the temperature when the component content of all the elements is qualified, and carrying out tapping operation when the temperature reaches the specified requirement. After tapping, the sedation time in the ladle is ensured to be not less than 5 min.

7. Pouring operation: the pouring temperature and the pouring speed are determined according to the process requirements of the casting, and the initial pouring temperature is preferably not higher than 1600 ℃. And when all conditions are met, casting molding and pouring operation can be carried out, and the steel casting is manufactured.

The smelting process of the medium-frequency induction furnace can also refer to the prior art, and preferably refers to the following processes:

1. preparing furnace burden: because the intermediate frequency furnace does not have the functions of decarburization, dephosphorization and desulfurization, and the tendencies of dephosphorization and desulfurization are reached in the later stage of smelting, the components of the scrap steel entering the furnace must be controlled to smelt the required molten steel.

2. Performing shot blasting treatment on the prepared furnace charge to ensure the cleanness of the waste steel entering the furnace, and simultaneously baking other furnace entering raw materials such as ferrochromium, ferromolybdenum, ferromanganese, ferrosilicon, pure aluminum blocks, silicon-calcium alloy and the like for 2 hours at the temperature of 450 ℃.

3. Firstly adding small lump waste steel, protecting furnace bottom, then adding high-melting-point alloy of ferrochromium and ferromolybdenum, and then adding large lump waste steel. And melting the furnace burden at full power. After the steel ingot is melted and cleaned, the main alloys of carbon, silicon, manganese, chromium, molybdenum, niobium and the like are adjusted to be within the target range.

4. And adjusting the temperature of the molten steel to the tapping temperature, adding a pure aluminum block into the ladle, tapping, and pouring. And finishing the manufacturing of the steel casting.

In a preferred embodiment of the present application, the high-temperature normalizing treatment includes heating the steel casting to 951-1050 ℃, keeping the temperature for 2-6 hours, discharging the steel casting, and air cooling to room temperature. Because the grain refinement technology of the aluminum niobium nitrogen is adopted, the aluminum niobium nitrogen alloy can be heated at high temperature to ensure that the components of the whole casting are uniform and consistent, thereby ensuring the consistent performance.

In another preferred embodiment of the present invention, the quenching treatment includes heating the steel casting after the high-temperature normalizing treatment to 930-950 ℃ and preserving the heat for 2-5 hours, then discharging and cooling, wherein the cooling rate in the quenching treatment is controlled to be 10.1-100 ℃/s, and preferably, the cooling medium used in the cooling is a sodium chloride aqueous solution or water containing 5-15%. This will give the steel casting a predominantly quenched martensitic microstructure throughout its cross-section. And then tempering the steel casting after quenching treatment to obtain the required comprehensive mechanical property.

In another preferred embodiment of the present invention, the tempering treatment includes heating the quenched steel casting to 630-680 ℃, keeping the temperature for 2-7 hours, then discharging the steel casting from the furnace and cooling the steel casting to room temperature, and the cooling in the tempering treatment is performed in air, oil, water or a water-soluble medium. The tempering temperature is above 630 ℃, so that the casting has more excellent plasticity and toughness. The tempering treatment obtains a metallographic structure mainly comprising tempered sorbite.

In yet another exemplary embodiment of the present application, a railway component is provided, which is formed by molding the alloy cast steel described above.

The mechanical property of the cast steel can meet the requirements in the table 1, so that the railway parts using the cast steel can better adapt to the requirements of high and cold environments. Preferably, the railway parts comprise a coupler seat, a coupler, a clamp, a brake disc, a shaft box body, a gear box, a coupler yoke, a bogie, a framework, a star plate, a shaft and a support shaft.

The cast steel of the present application can be produced into other parts requiring the same mechanical properties and high weldability, or parts in other fields requiring light weight and high strength, and is preferably a welded frame, a shaft, a support shaft, and the like.

The advantageous effects of the present application will be further described below with reference to examples and comparative examples.

In the present invention, the mechanical properties are measured according to the A.A.R standard, American railway Association standards M-201-05, and the samples used are based on Kerr test blocks. Where CE ═ C + (Mn + Si)/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15.

In the following examples, the contents of the components are in terms of the mass% thereof.

Example 1

The low-alloy cast steel for low temperature with low carbon equivalent comprises the following components in percentage by mass: 0.17% of carbon, 0.24% of silicon, 1.36% of manganese, 0.012% of phosphorus, 0.009% of sulfur, 0.22% of chromium, 0.33% of molybdenum, 0.04% of aluminum, 0.03% of niobium, 163ppm of nitrogen, and the balance other unavoidable elements. The carbon equivalent was 0.55%.

In the embodiment, the steel casting is obtained by adopting the electric arc smelting process, and the post-heat treatment process of the steel casting adopts high-temperature normalizing and quenching and tempering treatment. Specifically, the high-temperature normalizing treatment process comprises the steps of heating a steel casting to 980 ℃ and preserving heat for 3 hours, and then discharging the steel casting out of a furnace for air cooling; the quenching process is that the steel casting after high temperature normalizing is heated to 930 ℃ and is kept warm for 2 hours, the steel casting is taken out of the furnace and is cooled to room temperature in a 10 percent sodium chloride water solution, and the integral cooling speed of the cast steel is 42.5 ℃/s. The tempering process comprises the steps of heating the quenched steel casting to 650 ℃, preserving heat for 5.0 hours, discharging the steel casting out of the furnace, and cooling the steel casting to room temperature in water.

After the low-alloy cast steel of the above example 1 is processed, the obtained metallographic structure is mainly tempered sorbite, the specific metallographic structure pattern is shown in fig. 1 and fig. 2, the typical metallographic morphology of tempered sorbite can be seen from fig. 1 and fig. 2, and the grain size is obviously refined and the structure uniformity is very good.

The mechanical properties of the low alloy cast steel of example 1 above (after the above heat treatment) were measured to obtain the following test results: 731MPa tensile strength, 614MPa yield strength, 25.5% elongation, 54% reduction of area, 116J Charpy V-type impact energy at-40 deg.C (average value), 101J Charpy V-type impact energy at-50 deg.C (average value), 92J Charpy V-type impact energy at-60 deg.C (average value), and 212HBW hardness.

Examples 2 to 21 and comparative examples 1 to 5

The processes of examples 2 to 16 are the same as those of example 1, the specific components, contents and carbon equivalent are shown in Table 2, the formulations of examples 17 to 21 are the same as those of example 1, and the heat treatment processes are as follows. Wherein the data of comparative examples 1 to 3 are derived from the relevant data of CN103436807B and comparative examples 4 to 5 are derived from the inventors experimental data.

Example 17

In the embodiment, the steel casting is obtained by adopting the electric arc smelting process, and the post-heat treatment process of the steel casting adopts high-temperature normalizing and quenching and tempering treatment. Specifically, the high-temperature normalizing treatment process comprises the steps of heating a steel casting to 951 ℃ and preserving heat for 6 hours, and then discharging the steel casting out of a furnace for air cooling; the quenching process is that the steel casting after high temperature normalizing is heated to 939 ℃ and is kept warm for 3 hours, and the steel casting is taken out of the furnace and is cooled to room temperature in an aqueous solution containing 8 percent of sodium chloride, and the integral cooling speed of the cast steel is 31.5 ℃/s. The tempering process comprises the steps of heating the quenched steel casting to 645 ℃, preserving heat for 6.0 hours, discharging the steel casting out of the furnace, and cooling the steel casting to room temperature in oil.

Example 18

In the embodiment, the steel casting is obtained by adopting the electric arc smelting process, and the post-heat treatment process of the steel casting adopts high-temperature normalizing and quenching and tempering treatment. Specifically, the high-temperature normalizing treatment process comprises the steps of heating a steel casting to 970 ℃, preserving heat for 4 hours, and then discharging the steel casting out of a furnace for air cooling; the quenching process is that the steel casting after high temperature normalizing is heated to 950 ℃ and is kept warm for 2 hours, the steel casting is taken out of the furnace and is cooled to room temperature in a 15 percent sodium chloride water solution, and the integral cooling speed of the cast steel is 98.7 ℃/s. The tempering process comprises the steps of heating the quenched steel casting to 630 ℃, preserving heat for 7.0 hours, discharging the steel casting out of the furnace, and cooling the steel casting to room temperature in air.

Example 19

In the embodiment, the steel casting is obtained by adopting the electric arc smelting process, and the post-heat treatment process of the steel casting adopts high-temperature normalizing and quenching and tempering treatment. Specifically, the high-temperature normalizing treatment process comprises the steps of heating a steel casting to 1050 ℃ and preserving heat for 3 hours, and then discharging the steel casting out of a furnace for air cooling; the quenching process is that the steel casting after high temperature normalizing is heated to 930 ℃ and is kept warm for 6 hours, the steel casting is taken out of the furnace and is cooled to room temperature in an aqueous solution containing 5 percent of sodium chloride, and the integral cooling speed of the cast steel is 17.2 ℃/s. The tempering process is that the steel casting after quenching treatment is heated to 680 ℃ and is kept warm for 2.0 hours, and then the steel casting is taken out of the furnace and is cooled to room temperature in a water solvent medium.

Example 20

In the embodiment, the steel casting is obtained by adopting the electric arc smelting process, and the post-heat treatment process of the steel casting adopts high-temperature normalizing and quenching and tempering treatment. Specifically, the high-temperature normalizing treatment process comprises the steps of heating a steel casting to 960 ℃ and preserving heat for 6 hours, and then discharging the steel casting from a furnace for air cooling; the quenching process is that the steel casting after high temperature normalizing is heated to 940 ℃ and is kept warm for 2 hours, the steel casting is taken out of the furnace and is cooled to room temperature in an aqueous solution containing 12 percent of sodium chloride, and the integral cooling speed of the cast steel is 86.6 ℃/s. The tempering process comprises the steps of heating the steel casting after quenching treatment to 665 ℃, preserving heat for 5.0 hours, discharging the steel casting out of the furnace, and cooling the steel casting in water to room temperature.

Example 21

In the embodiment, the steel casting is obtained by adopting the electric arc smelting process, and the post-heat treatment process of the steel casting adopts high-temperature normalizing and quenching and tempering treatment. Specifically, the high-temperature normalizing treatment process comprises the steps of heating a steel casting to 960 ℃ and preserving heat for 3 hours, and then discharging the steel casting from a furnace for air cooling; the quenching process is that the steel casting after high-temperature normalizing is heated to 930 ℃ and is kept warm for 2 hours, the steel casting is taken out of the furnace and is cooled to room temperature in water, and the integral cooling speed of the cast steel is 10.5 ℃/s. The tempering process comprises the steps of heating the quenched steel casting to 630 ℃, preserving heat for 6.0 hours, discharging the steel casting out of the furnace, and cooling the steel casting to room temperature in water.

Table 2 (mass%)

The results of mechanical property tests of the cast steels of each example and comparative example are shown in table 3.

TABLE 3 mechanical Properties

From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:

cast steel formed of the cast steel material having the above composition has improved strength of cast steel due to appropriate contents of carbon, manganese, molybdenum and chromium; meanwhile, other elements are controlled to be matched with the nickel-based alloy at proper content, so that the strength of the cast steel is improved and the low-temperature toughness of the cast steel is improved without adopting a nickel precursor.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.