阅读说明：本技术 一种控制非调质钢大颗粒夹杂物的制备方法 (Preparation method for controlling large-particle inclusions in non-quenched and tempered steel ) 是由 殷天颖 胡志勇 周杨 鲁川 陈鹏涛 刘义 于 2020-03-10 设计创作，主要内容包括：本发明公开了一种控制非调质钢大颗粒夹杂物的制备方法,包括以下步骤：(1)转炉冶炼：进行转炉冶炼过程中,控制转炉终点C质量百分含量≥0.10％或出钢TSO氧位≤300ppm,出钢温度≥1600℃；(2)转炉出钢：钢水出钢前开启转炉底搅,降低钢水氧化性以及钢水的P含量；在出钢前期加入碳粉进行预脱氧,再顺序加入脱氧剂、合金及渣料进行脱氧合金化,在脱氧合金化过程中保持全程吹氮气,出钢后期采取双挡方式出钢,严格控制下渣。本发明的非调质钢可稳定控制全氧15ppm以下,H含量1.5ppm以下,有效降低钢中H和O含量,提高产品质量,保证生产的汽车用钢具有低全O、H以及较高的纯净度水平,保证非调质汽车用钢具有优良的抗疲劳破坏性能。(The invention discloses a preparation method for controlling large-particle inclusions in non-quenched and tempered steel, which comprises the following steps of: (1) smelting in a converter: in the process of smelting the converter, controlling the mass percentage content of the end point C of the converter to be more than or equal to 0.10 percent or the oxygen site of the tapped TSO to be less than or equal to 300ppm and the tapping temperature to be more than or equal to 1600 ℃; (2) tapping by a converter: before molten steel tapping, the bottom of a converter is opened for stirring, so that the oxidability of the molten steel and the P content of the molten steel are reduced; adding carbon powder for pre-deoxidation at the early stage of tapping, sequentially adding a deoxidizer, an alloy and slag charge for deoxidation alloying, keeping full-process nitrogen blowing in the deoxidation alloying process, tapping at the later stage of tapping in a double-gear mode, and strictly controlling slag tapping. The non-quenched and tempered steel can be stably controlled to be below 15ppm of total oxygen and below 1.5ppm of H, the H and O content in the steel is effectively reduced, the product quality is improved, the produced automobile steel is guaranteed to have low total O, H and higher purity level, and the non-quenched and tempered automobile steel is guaranteed to have excellent fatigue failure resistance.)

1. The preparation method for controlling large-particle inclusions in non-quenched and tempered steel is characterized by comprising the following steps of:

(1) smelting in a converter: in the process of smelting the converter, controlling the mass percentage content of the end point C of the converter to be more than or equal to 0.10 percent or the oxygen site of the tapped TSO to be less than or equal to 300ppm and the tapping temperature to be more than or equal to 1600 ℃;

(2) tapping by a converter: before molten steel tapping, the bottom of a converter is opened for stirring, so that the oxidability of the molten steel and the P content of the molten steel are reduced; adding carbon powder for pre-deoxidation at the early stage of tapping, sequentially adding a deoxidizer, an alloy and slag charge for deoxidation alloying, keeping full-process nitrogen blowing in the deoxidation alloying process, tapping at the later stage of tapping in a double-gear mode, and strictly controlling slag tapping;

(3) l F furnace refining, wherein the refining time is more than or equal to 40min, lime and refining slag are added in the refining, and the percentage content of inclusions in the steel is controlled to be 45-60% of CaO and SiO₂10 to 20% of Al₂O₃15-25%, controlling the final slag alkalinity at 3.0-4.0, performing composite diffusion deoxidation by using SiC, aluminum wires or calcium carbide in the power supply smelting process, ensuring that the total mass percentage of TFe and MnO is less than or equal to 0.80%, keeping white slag in the process, and ensuring that the oxygen content is less than 5ppm when the slag is out of the station;

(4) RH vacuum: controlling the vacuum degree below 2.5 mbar, keeping the vacuum for more than 15min, adding nitrogen components by using a silicon-nitrogen alloy and a composite vanadium-nitrogen alloy, forbidding calcium treatment, and soft-blowing for more than 20 min;

(5) continuous casting: casting through continuous casting to obtain non-quenched and tempered steel, and controlling the superheat degree of a continuous casting tundish to be 10-35 ℃.

2. The method for preparing large-particle inclusions in non-quenched and tempered steel according to claim 1, wherein the method comprises the following steps: in the step (2), the alloy is ferrosilicon and ferromanganese, the deoxidizer is an aluminum block, and the slag is lime.

3. The method for preparing large-particle inclusions in non-quenched and tempered steel according to claim 1, wherein the method comprises the following steps: and (3) reducing the P content to below 0.025 percent by bottom stirring of the discharged steel of the converter in the step (2).

4. The method for preparing large-particle inclusions in non-quenched and tempered steel according to claim 1, wherein the method comprises the following steps: and (3) in the step (2), the double-gear mode is a mode of adding a slag blocking cone by a sliding plate or adding a slag blocking ball by a sliding plate, so that the slag discharge during the converter tapping is effectively reduced.

5. The method for preparing large-particle inclusions in non-quenched and tempered steel according to claim 1, wherein the method comprises the following steps: and (3) adding a slag fishing and raking process after tapping in the step (2) to ensure that the slag amount of the converter is less than or equal to 2 kg/ton of steel.

6. The method for preparing large-particle inclusions in non-quenched and tempered steel according to claim 1, wherein the method comprises the following steps: the non-quenched and tempered steel comprises the following chemical components in percentage by weight: c: 0.42 to 0.49%, Si: 0.3-0.6%, Mn: 1.0-1.5%, P: less than or equal to 0.025%, S: 0.035-0.075%, V: 0.06-0.13%, Alt: 0.005-0.025%, Ni is less than or equal to 0.3%, Cu is less than or equal to 0.3%, Cr is less than or equal to 0.3%, and N: not less than 80ppm, and the balance of Fe and inevitable impurities.

Technical Field

The invention belongs to the technical field of production of non-quenched and tempered steel, and particularly relates to a preparation method for controlling large-particle inclusions in the non-quenched and tempered steel.

Background

With the progress of automobile manufacturing, the requirements of parts such as automobile crankshafts, connecting rods and the like on non-quenched and tempered steel materials are continuously improved, and the materials are required to have good processing performance, high strength, high toughness and the like. The strength of the non-quenched and tempered steel is controlled in a proper range mainly by adding trace elements such as Nb, Ti, V and the like and combining with a subsequent forging and cooling control process.

The inclusions of the non-quenched and tempered steel are mainly composite inclusions containing Al, Ca, O and S, the external dimension is cluster-shaped inclusions with the width or the diameter of 50-200 um, wherein the large-particle inclusions in the clusters are small in size and are fine inclusions smaller than 19um (equivalent to DS class 0.5). The flaw detection yield of the round steel is less than 70% because a large amount of cluster-shaped inclusions are generated in the steel.

CN201811308589.6, the name of which is that the production mode of reducing large-particle inclusions in steel by converter-L F-RH-continuous casting is mainly introduced, and the method has the defects that the control of gaseous elements and inclusions such as O, H in the steel is difficult, and the stability and the service life of products are influenced.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a preparation method for controlling large-particle inclusions in non-quenched and tempered steel, and solves the problem that the mechanical properties of the non-quenched and tempered steel are poor due to insufficient control of gaseous elements such as O, H and the inclusions in the conventional non-quenched and tempered steel. The non-quenched and tempered steel prepared by the method has the advantages of less large-particle inclusions, good mechanical property and strong fatigue failure resistance.

The technical scheme is as follows: the invention relates to a preparation method for controlling large-particle inclusions in non-quenched and tempered steel, which comprises the following steps of:

(1) smelting in a converter: in the process of smelting the converter, controlling the mass percentage content of the end point C of the converter to be more than or equal to 0.10 percent or the oxygen site of the tapped TSO to be less than or equal to 300ppm and the tapping temperature to be more than or equal to 1600 ℃;

(2) tapping by a converter: before molten steel tapping, the bottom of a converter is opened for stirring, so that the oxidability of the molten steel and the P content of the molten steel are reduced; adding carbon powder for pre-deoxidation at the early stage of tapping, sequentially adding a deoxidizer, an alloy and slag charge for deoxidation alloying, keeping full-process nitrogen blowing in the deoxidation alloying process, tapping at the later stage of tapping in a double-gear mode, and strictly controlling slag tapping;

(3) l F furnace refining, wherein the refining time is more than or equal to 40min, lime and refining slag are added in the refining, and the percentage content of inclusions in the steel is controlled to be 45-60% of CaO and SiO₂10 to 20% of Al₂O₃15-25%, controlling the final slag alkalinity at 3.0-4.0, performing composite diffusion deoxidation by using SiC, aluminum wires or calcium carbide in the power supply smelting process, ensuring that the total mass percentage of TFe and MnO is less than or equal to 0.80%, keeping white slag in the process, and ensuring that the oxygen content is less than 5ppm when the slag is out of the station;

(4) RH vacuum: controlling the vacuum degree below 2.5 mbar, keeping the vacuum for more than 15min, adding nitrogen components by using a silicon-nitrogen alloy and a composite vanadium-nitrogen alloy, forbidding calcium treatment, and soft-blowing for more than 20 min;

(5) continuous casting: casting through continuous casting to obtain non-quenched and tempered steel, and controlling the superheat degree of a continuous casting tundish to be 10-35 ℃.

Further, it is characterized in that: in the step (2), the alloy is ferrosilicon and ferromanganese, the deoxidizer is an aluminum block, and the slag is lime.

Further, it is characterized in that: and (3) reducing the P content to below 0.025 percent by bottom stirring of the discharged steel of the converter in the step (2).

Further, it is characterized in that: and (3) in the step (2), the double-gear mode is a mode of adding a slag blocking cone by a sliding plate or adding a slag blocking ball by a sliding plate, so that the slag discharge during the converter tapping is effectively reduced.

Further, it is characterized in that: and (3) adding a slag fishing and raking process after tapping in the step (2) to ensure that the slag amount of the converter is less than or equal to 2 kg/ton of steel.

Further, it is characterized in that: the non-quenched and tempered steel comprises the following chemical components in percentage by weight: c: 0.42 to 0.49%, Si: 0.3-0.6%, Mn: 1.0-1.5%, P: less than or equal to 0.025%, S: 0.035-0.075%, V: 0.06-0.13%, Alt: 0.005-0.025%, Ni is less than or equal to 0.3%, Cu is less than or equal to 0.3%, Cr is less than or equal to 0.3%, and N: not less than 80ppm, and the balance of Fe and inevitable impurities.

The invention has the beneficial effects that: the non-quenched and tempered steel can be stably controlled to be below 15ppm of total oxygen and below 1.5ppm of H, the H and O content in the steel is effectively reduced, the product quality is improved, the produced automobile steel is guaranteed to have low total O, H and higher purity level, and the non-quenched and tempered automobile steel is guaranteed to have excellent fatigue failure resistance.

Detailed Description

The invention is further described below with reference to examples:

the non-quenched and tempered steel prepared by the invention comprises the following chemical components in percentage by weight: c: 0.42 to 0.49%, Si: 0.3-0.6%, Mn: 1.0-1.5%, P: less than or equal to 0.025%, S: 0.035-0.075%, V: 0.06-0.13%, Alt: 0.005-0.025%, Ni is less than or equal to 0.3%, Cu is less than or equal to 0.3%, Cr is less than or equal to 0.3%, and N: not less than 80ppm, and the balance of Fe and inevitable impurities.

The preparation method comprises the following steps: