CN108060356B - Preparation method of niobium-nitrogen microalloyed ledge cast steel - Google Patents
Preparation method of niobium-nitrogen microalloyed ledge cast steel Download PDFInfo
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- CN108060356B CN108060356B CN201711328072.9A CN201711328072A CN108060356B CN 108060356 B CN108060356 B CN 108060356B CN 201711328072 A CN201711328072 A CN 201711328072A CN 108060356 B CN108060356 B CN 108060356B
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
Abstract
The invention discloses a preparation method of niobium-nitrogen microalloyed ledge cast steel, belonging to the technical field of metallurgy. The preparation method mainly comprises the steps of material preparation, steel making in an induction furnace, casting molding, quenching and tempering heat treatment and the like. During steel making in an induction furnace, the carbon content in the melting period is controlled to be below 0.08%, the microalloy element niobium is added in the refining period, nitrogen is filled into molten steel through an air brick arranged at the bottom of a crucible, and then the carbon content is adjusted according to the component requirement. The ledge cast steel prepared by the method comprises the following main chemical components in percentage by weight: c: 0.26-0.35%; si: 0.60-0.90%; mn: 1.10-2.00%; p is less than or equal to 0.010 percent; s: less than or equal to 0.010 percent; nb: 0.02-0.06%; Nb/N is more than 7-9, and the balance is Fe. The ledge cast steel prepared by the treatment can ensure that niobium is mainly precipitated in a nitride form and reduce the precipitation of niobium carbide, and the cast steel has the tensile strength of over 900MPa and the impact toughness of 50J/cm2Above, the requirements of the ledge cast steel on high strength and toughness indexes are met.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and relates to a preparation method of niobium-nitrogen microalloyed ledge cast steel.
Background
The middle trough is the main part of the scraper conveyor, and each scraper conveyor usually has 100 sections of middle troughs, which account for 70% -80% of the whole scraper conveyor by weight or cost, so the middle trough is the part with the largest usage amount and consumption amount. Each section of the middle groove is generally formed by integrally casting a shovel plate ledge and a baffle plate ledge, and assembling and welding a high-strength wear-resistant alloy middle plate and a bottom plate. The ledge is positioned on two sides of the middle groove, comprises a shovel board ledge, a baffle ledge and a small number of special-shaped ledges and is structurally formed by integral casting.
At present, ZG30MnSi is generally adopted as a ledge material, and because the toughness is low, the wear resistance is poor, the coal passing amount is generally about 600 ten thousand tons and is lower than the foreign level of more than 1500 ten thousand tons, the requirement of a large-mining-height coal face is difficult to meet, the economic benefit of a coal production enterprise is seriously restricted by too fast scrapping and frequent replacement, and the development of the high-reliability ledge has important significance and value.
For this reason, ledge materials have been developed based on ZG30MnSi chemistry by adding alloying elements such as Ni, Cr, Mo and rare earths, with a maximum strength of 1800MPa and a corresponding hardness of 55.1HRC, but with too low a toughness of only 15J/cm-2The matching of the obdurability is not reasonable, and the practice shows that the use effect of the ledge material is not ideal. Some materials have higher toughness but lower strength, which can not meet the requirements of ledge materials.
Niobium is the most effective microalloying element in steel, has stronger action than Ti and V in steel, has rich reserves and low price, and has great application prospect. The niobium is added into the steel, so that the strength and the toughness of the steel can be improved, the wear resistance and the corrosion resistance of the steel can be improved, the brittle transition temperature of the steel can be reduced, and the like.
Therefore, the application realizes reasonable matching of the toughness and toughness by using the commonly used ledge material ZG30MnSi as the basis and through the microalloying effect of niobium and nitrogen, thereby achieving the high toughness of the ledge cast steel. Meanwhile, considering that the carbide size of niobium is large when the carbon content is high, which not only is adverse to the performance of cast steel, but also affects the grain refining effect of niobium, a preparation method mainly aiming at increasing the precipitation amount of niobium nitride is proposed in order to fully exert the microalloying effect of niobium.
Disclosure of Invention
The preparation method of niobium-nitrogen microalloyed ledge cast steel is mainly aimed at increasing the precipitation quantity of niobium nitride. The preparation method comprises the steps of controlling the carbon content in the melting period during the steel making of the induction furnace, adding niobium in the refining period, simultaneously performing nitrogen filling treatment, and then adjusting the carbon content.
The invention is realized by the following technical measures:
a preparation method of niobium-nitrogen microalloyed ledge cast steel is characterized by comprising the following steps: the materials are prepared by proportioning specified components and carrying out the processes of steel making by an induction furnace, casting molding and quenching and tempering heat treatment;
during steel making in an induction furnace, the carbon content in the melting period is controlled to be below 0.08%, the microalloy element niobium is added in the refining period, nitrogen is filled into the molten steel through the air brick arranged at the bottom of the crucible, and after the ratio of the niobium content to the nitrogen content in the molten steel is ensured to be within the range of 7-9, the carbon content is adjusted according to the component requirement.
Furthermore, the carbon content in the melting period is controlled to be below 0.08 percent, so as to ensure that niobium in the cast steel is precipitated in the form of nitride; the carbon content is ensured by controlling the carbon content during batching and the oxidation during steelmaking.
Further, the chemical components and the mass percentage content of the niobium-nitrogen microalloyed ledge cast steel are controlled as follows: c: 0.26-0.35%; si: 0.60-0.90%; mn: 1.10-2.00%; p is less than or equal to 0.025 percent; s: less than or equal to 0.025 percent; nb: 0.02-0.06%; Nb/N is more than 7-9; the balance being Fe.
The Nb/N is more than 7-9, and the niobium in the cast steel is mainly precipitated in the form of nitride from the aspect of components.
Further, the casting molding process comprises the following steps: the casting temperature is 1550-1580 ℃, and the casting speed is 70-80 m/s. The pouring temperature and the pouring speed are controlled to avoid the rapid growth of the cast steel grains and influence the effect of the refined grains of the niobium nitrides.
Further, the quenching and tempering heat treatment process comprises the following steps: the quenching temperature is 870-890 ℃, and the tempering temperature is 500-520 ℃. The components of the steel grade can achieve the best effect only under the condition of the quenching and tempering process specified by the invention, and the niobium-nitrogen microalloying groove is ensuredThe steel can reach the tensile strength of over 900MPa and the impact toughness of 50J/cm2Above, the requirements of the ledge cast steel on high strength and toughness indexes are met.
The invention has the beneficial effects that:
the preparation method provided by the invention can ensure that niobium is mainly precipitated in a nitride form, reduces the precipitation of niobium carbide, has the tensile strength of over 900MPa and the impact toughness of 50J/cm2Above, the requirements of the ledge cast steel on high strength and toughness indexes are met.
Detailed Description
Embodiments of the present invention will now be described in detail.
The embodiments further describe the technical solution of the present invention. The examples are intended to illustrate the invention only and are not intended to limit the invention in any way.
The invention provides a preparation method of niobium-nitrogen microalloyed ledge cast steel, which is mainly carried out after the technical processes of material preparation, steel making by an induction furnace, casting molding, quenching and tempering heat treatment and the like are mainly utilized. During steel making in an induction furnace, the carbon content in the melting period is controlled to be below 0.08%, the microalloy element niobium is added in the refining period, nitrogen is filled into the molten steel through the air brick arranged at the bottom of the crucible, and after the ratio of the niobium content to the nitrogen content in the molten steel is ensured to be within the range of 7-9, the carbon content is adjusted according to the component requirement. When the chemical components meet the design requirements through sampling test, finishing steelmaking and transferring to the next procedure for casting molding, wherein the casting molding temperature is 1550-1580 ℃, and the casting speed is 70-80 m/s; and (3) after air cooling to room temperature and demoulding, carrying out quenching and tempering heat treatment, wherein the quenching temperature is 870-890 ℃, and the tempering temperature is 500-520 ℃. The ledge cast steel comprises the following chemical components in percentage by mass: c: 0.23-0.35%; si: 0.60-0.90%; mn: 1.10-2.00%; p is less than or equal to 0.025 percent; s: less than or equal to 0.025 percent; nb: 0.02-0.06%; Nb/N is more than 7-9; the balance being Fe.
Example 1
The ingredients are mixed according to the chemical components, and the carbon content is 0.06 percent during the mixing. Then, carrying out steel making in an induction furnace, and ensuring that the carbon content in the melting period is not higher than 0.08% through oxidation; 0.04 percent of microalloy element niobium is added in the later stage of the refining period, meanwhile, nitrogen is filled into the molten steel through the air brick arranged at the bottom of the crucible, and after the content of the nitrogen reaches 0.0056 percent, the carbon content is adjusted according to the component requirement. When the chemical components meet the design requirements through sampling test, the steel making is finished and the next procedure is carried out for casting molding, wherein the casting molding temperature is 1570 ℃, and the casting speed is 72 m/s; air cooling to room temperature, demoulding, and quenching and tempering heat treatment at 880 ℃ and 510 ℃. The chemical components (mass fraction/%) measured after steel making in this example are: 0.25C, 0.7Si,1.22Mn, 0.012S, 0.011P, 0.035Nb, 0.004N.
The ledge prepared by the method is sampled and analyzed, and the result shows that the metallographic structure observation result shows that niobium carbide is not observed, the mechanical property test result shows that the tensile strength exceeds 920MPa, and the impact toughness reaches 56J/cm2The above results show that the ledge cast steel has higher strength and toughness.
Example 2
The ingredients are mixed according to the chemical components, and the carbon content is 0.07 percent during the mixing. Then, carrying out steel making in an induction furnace, and ensuring that the carbon content in the melting period is not higher than 0.08% through oxidation; 0.06 percent of microalloy element niobium is added in the later stage of the refining period, and meanwhile, nitrogen is filled into the molten steel through the air brick arranged at the bottom of the crucible, and after the content of the nitrogen reaches 0.0086 percent, the carbon content is adjusted according to the component requirement. When the chemical components meet the design requirements through sampling test, the steel making is finished and the next procedure is carried out for casting molding, wherein the casting molding temperature is 1560 ℃, and the casting speed is 75 m/s; air cooling to room temperature, demoulding, and quenching and tempering heat treatment at 870 ℃ and 500 ℃. The chemical components (mass fraction/%) measured after steel making in this example are: 0.31C, 0.8Si,1.62Mn, 0.019S, 0.020P, 0.056Nb, 0.0079N.
The ledge prepared by the method is sampled and analyzed, and the result shows that the observation result of metallographic structure shows that no niobium carbide is observed, the test result of mechanical property shows that the tensile strength exceeds 1010MPa, and the impact toughness reaches52J/cm2The above results show that the ledge cast steel has higher strength and toughness.
The embodiment shows that the ledge prepared by the preparation method of the niobium-nitrogen microalloyed ledge cast steel provided by the invention ensures that niobium is mainly precipitated in a nitride form, so that the microalloying effect of the niobium is greatly improved, and as a result, the ledge obtains higher toughness index and meets the service requirement of the ledge cast steel.
Claims (3)
1. A preparation method of niobium-nitrogen microalloyed ledge cast steel is characterized by comprising the following steps: the ledge cast steel is prepared by burdening according to specified components and carrying out the processes of steel making by an induction furnace, casting molding and quenching and tempering heat treatment;
during steel making in an induction furnace, the carbon content in the melting period is controlled to be below 0.08%, nitrogen is filled into the molten steel through a gas permeable brick arranged at the bottom of a crucible while the microalloy element niobium is added in the refining period, and after the ratio of the niobium content to the nitrogen content in the molten steel is ensured to be within the range of 7-9, the carbon content is adjusted according to the component requirement;
the niobium-nitrogen microalloyed ledge cast steel comprises the following chemical components in percentage by mass: c: 0.26-0.35%; si: 0.60-0.90%; mn: 1.10-2.00%; p is less than or equal to 0.025 percent; s: less than or equal to 0.025 percent; nb: 0.02-0.06%; the balance of Fe;
the prepared niobium-nitrogen microalloyed ledge cast steel has the tensile strength of over 900MPa and the impact toughness of 50J/cm2The requirements of the ledge cast steel on high strength and toughness indexes are met;
the carbon content in the melting period is controlled to be below 0.08 percent, so as to ensure that niobium in the cast steel is precipitated in a nitride form; the carbon content is ensured by controlling the carbon content during batching and the oxidation during steelmaking.
2. The method for preparing niobium-nitrogen microalloyed ledge cast steel according to claim 1, characterized in that: the casting molding process comprises the following steps: the casting temperature is 1550-1580 ℃, and the casting speed is 70-80 m/s.
3. The method for preparing niobium-nitrogen microalloyed ledge cast steel according to claim 1, characterized in that: the quenching and tempering heat treatment process comprises the following steps: the quenching temperature is 870-890 ℃, and the tempering temperature is 500-520 ℃.
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| CN109182691B (en) * | 2018-10-17 | 2020-02-07 | 北京科技大学 | Heat treatment method of microalloyed medium carbon cast steel |
| CN112981068B (en) * | 2021-02-02 | 2022-02-11 | 北京科技大学 | Method for improving toughness of microalloyed ledge steel casting by utilizing deformation induced precipitation |
| CN115233091A (en) * | 2022-06-23 | 2022-10-25 | 中煤张家口煤矿机械有限责任公司 | Novel microalloyed ledge cast steel and preparation method thereof |
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| CN103966515B (en) * | 2014-05-28 | 2016-02-03 | 河南理工大学 | A kind of method utilizing electric arc furnace to prepare low-alloy high-strength toughness cast steel adding |
| CN104911453B (en) * | 2015-06-26 | 2018-02-27 | 上海宏钢电站设备铸锻有限公司 | A kind of preparation technology of the cast steel material of 620 DEG C of high temperature resistant |
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