阅读说明：本技术 一种提高低合金高强度耐磨钢中有效硼含量的方法 (Method for increasing effective boron content in low-alloy high-strength wear-resistant steel ) 是由 韩健 张卫攀 刘红艳 陈子刚 杜琦铭 徐桂喜 王青云 周文涛 于 2020-11-02 设计创作，主要内容包括：一种提高低合金高强度耐磨钢中有效硼含量的方法,包括(1)转炉冶炼：进行脱磷操作,全程底吹氩气,一倒后点吹氧气≤500m～3,避免过吹,钢包中加入铝块和白灰进行前期脱氧和造渣处理,TO≤80ppm,N≤30ppm；(2)LF精炼：向钢包中喂入铝线,保证钢液中酸溶铝为0.03～0.05wt%,造白渣脱硫后加入钛铁,3分钟后加入硼铁,钢包底吹氩气；(3)RH真空处理：处理时间≥35min,精炼结束后,钢液中N≤40ppm；(4)板坯连铸：中间包开浇前采用氩气吹扫,开浇后采用双层覆盖剂,保护浇注。本发明通过控制钢液中氧和氮含量,减少酸不溶硼产生,进而增加有效硼含量,使钢坯中有效硼含量达到85%以上。(A method for improving the effective boron content in low-alloy high-strength wear-resistant steel comprises the following steps of (1) converter smelting: the dephosphorization operation is carried out, and the dephosphorization operation is carried out,argon bottom blowing is carried out in the whole process, and oxygen is blown to be less than or equal to 500m at a point after one-time pouring 3 Avoiding over-blowing, adding aluminum blocks and lime into the ladle for early-stage deoxidation and slagging treatment, wherein TO is less than or equal TO 80ppm, and N is less than or equal TO 30 ppm; (2) LF refining: feeding an aluminum wire into a steel ladle to ensure that acid-soluble aluminum in molten steel is 0.03-0.05 wt%, adding ferrotitanium after desulfurizing the white slag, adding ferroboron after 3 minutes, and blowing argon at the bottom of the steel ladle; (3) RH vacuum treatment: the treatment time is more than or equal to 35min, and after the refining is finished, N in the molten steel is less than or equal to 40 ppm; (4) slab continuous casting: argon is adopted for blowing before pouring of the tundish, and a double-layer covering agent is adopted for protecting pouring after pouring. The invention reduces the generation of acid insoluble boron by controlling the content of oxygen and nitrogen in the molten steel, thereby increasing the effective boron content and leading the effective boron content in the steel billet to reach more than 85 percent.)

1. The method for improving the effective boron content in the low-alloy high-strength wear-resistant steel is characterized by comprising the working procedures of converter smelting, LF refining, RH vacuum treatment and slab continuous casting, and comprises the following specific steps:

(1) a converter smelting process: carrying out dephosphorization operation, and blowing argon gas from bottom in the whole process, wherein the flow of the argon gas is 200-400 m³H, after one-time-down point oxygen blowing is less than or equal to 500m³Avoiding over-blowing, adding aluminum blocks and lime into the ladle for early deoxidation and slagging treatment, wherein TO is less than or equal TO 80ppm, and N is less than or equal TO 30 ppm;

(2) an LF refining procedure: feeding an aluminum wire into a steel ladle to ensure that the content of acid-soluble aluminum in molten steel is 0.030-0.050%, adding ferrotitanium after the white slag desulfurization is finished, controlling the mass fraction ratio of omega (Ti)/omega (N) to be 3-4, blowing argon at the bottom of the steel ladle to keep small-gas soft blowing, and controlling the flow of argon to be 10-20 m³H, addingAdding ferrotitanium for 3min, adding ferroboron, adjusting the components and temperature, and blowing argon from the bottom of the steel ladle;

(3) RH vacuum treatment process: the total treatment time is more than or equal to 35min, and after the RH vacuum treatment is finished, the N in the molten steel is less than or equal to 40 ppm;

(4) and a slab continuous casting process: argon is adopted for blowing before pouring of the tundish, and a double-layer covering agent is adopted after pouring, and argon is blown to protect pouring by a sealing ring and a long water gap.

2. The method of increasing the effective boron content of a low alloy, high strength, wear resistant steel of claim 1, wherein: in the converter smelting process, the slag amount in the tapping process is less than or equal to 0.25 wt%.

3. The method of increasing the effective boron content of a low alloy, high strength, wear resistant steel of claim 2, wherein: in the LF refining process, the feeding amount of an aluminum wire is 200-300 m, and the time for blowing argon from the bottom is more than or equal to 5 min.

4. The method for increasing the effective boron content in the low-alloy high-strength wear-resistant steel according to claim 3, wherein in the RH vacuum treatment process, the vacuum degree is less than or equal to 100Pa, the vacuum treatment time is more than or equal to 20min, the pure degassing time is more than or equal to 8min, and the argon net blowing time of the molten steel after the RH vacuum treatment is more than or equal to 6 min.

5. The method for increasing the effective boron content in the low-alloy high-strength wear-resistant steel according to any one of claims 1 to 4, wherein in the slab continuous casting process, the flow of argon is 15 to 25 NL/min, a submerged nozzle is inserted into a crystallizer to a depth of 160 to 180mm, and casting is carried out at a constant speed.

Technical Field

The invention belongs to the technical field of steel making, and relates to a method for improving the effective boron content in low-alloy high-strength wear-resistant steel.

Background

The low-alloy high-strength wear-resistant steel has high wear resistance, high strength, high toughness and good welding performance, and is widely applied to mechanical equipment in the industries of coal mine, transportation, agriculture, building, food processing and the like.

The improvement of the core quality of the wear-resistant steel plate can obviously improve the wear resistance and prolong the service life of equipment, and the improvement mainly depends on the hardenability in the heat treatment production. In a chemical composition system, boron is an important element for improving hardenability, and the core hardness of the wear-resistant steel can be obviously improved by adding a small amount (generally 10-20 ppm). The boron content in the steel is total boron, including acid-soluble boron and acid-insoluble boron. The acid-soluble boron is effective boron which is willing to improve the hardenability of the steel plate, the acid-insoluble boron is nitrogen oxide which has no effect on the hardenability, and the generation of the acid-soluble boron should be avoided as much as possible in the production. In actual production, the problems that the content of acid-soluble boron in molten steel is low and the content of acid-insoluble boron is high exist after ferroboron is added, so that the hardenability is poor, and the hardness performance of the wear-resistant steel core is low.

Disclosure of Invention

The invention aims to provide a method for improving the effective boron content in low-alloy high-strength wear-resistant steel, which can improve the hardenability of a wear-resistant steel plate and ensure the hardness of the surface and the core.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

a method for improving the effective boron content in low-alloy high-strength wear-resistant steel comprises the working procedures of converter smelting, LF refining, RH vacuum treatment and slab continuous casting, and comprises the following specific steps:

(1) a converter smelting process: carrying out dephosphorization operation, and blowing argon gas from bottom in the whole process, wherein the flow of the argon gas is 200-400 m³H, after one-time-down point oxygen blowing is less than or equal to 500m³Avoiding over-blowing, adding aluminum blocks and lime into the ladle for early deoxidation and slagging treatment, wherein TO is less than or equal TO 80ppm, and N is less than or equal TO 30 ppm;

(2) an LF refining procedure: feeding an aluminum wire into a steel ladle to ensure that the content of acid-soluble aluminum in molten steel is 0.030-0.050%, adding ferrotitanium after the white slag desulfurization is finished, controlling the mass fraction ratio of omega (Ti)/omega (N) to be 3-4, blowing argon at the bottom of the steel ladle to keep small-gas soft blowing, and controlling the flow of argon to be 10-20 m³Adding ferrotitanium for 3min, then adding ferroboron, adjusting the components and the temperature, and then carrying out argon blowing operation at the bottom of the steel ladle;

(3) RH vacuum treatment process: the total treatment time is more than or equal to 35min, and after the RH vacuum treatment is finished, the N in the molten steel is less than or equal to 40 ppm;

(4) and a slab continuous casting process: argon is adopted for blowing before pouring of the tundish, and a double-layer covering agent is adopted after pouring, and argon is blown to protect pouring by a sealing ring and a long water gap.

In the converter smelting process, the slag amount in the tapping process is less than or equal to 0.25 wt%.

In the LF refining process, the feeding amount of an aluminum wire is 200-300 m, and the time for blowing argon from the bottom is more than or equal to 5 min.

In the RH vacuum treatment process, the vacuum degree is less than or equal to 100Pa, the vacuum treatment time is more than or equal to 20min, the pure degassing time is more than or equal to 8min, and the argon net blowing time of the molten steel after the RH vacuum treatment is more than or equal to 6 min.

In the slab continuous casting process, the flow of argon is 15-25 NL/min, the depth of a submerged nozzle inserted into a crystallizer is 160-180 mm, and casting is carried out at a constant speed.

In the converter smelting, on the basis of decarburization and dephosphorization, the total oxygen and nitrogen contents in the molten steel are reduced, and the generation of boron nitrogen oxides is reduced as much as possible after ferroboron is added in the LF refining process. The bottom-blown argon gas adopted can better and uniformly homogenize the components and temperature in the molten steel, and the oxygen and the carbon are fully contacted and reacted to generate carbon monoxide and carbon dioxide which float upwards in a bubble mode. The nitrogen dissolved in the molten steel forms nitrogen gas in full collision and also floats upwards to be discharged.

In the LF refining production, aluminum is used for deep deoxidation, ferrotitanium is added for nitrogen fixation, and ferroboron is added when the oxygen and nitrogen contents in molten steel are extremely low. The design mechanism is as follows: boron is relatively active in molten steel and is easily reacted with oxygen and nitrogen to generate nitrogen oxides. At 1600 ℃, the deoxidation capacity is in the order of Al > Ti > B from large to small, and the nitrogen fixation capacity is in the order of Ti > B > Al from large to small. Therefore, the addition order of the alloying elements is Al, Ti, B. After the aluminum is added, the content of acid-soluble aluminum in the molten steel is kept between 0.030 and 0.050 percent. The possibility of reaction between B and N can be reduced to the minimum by controlling the added omega (Ti)/omega (N) to be 3-4, the boron added into the steel is protected, the effective boron content is improved, and the hardenability of the steel plate is increased.

And in the RH vacuum treatment, nitrogen in the molten steel is continuously removed, the generation of boron nitride is reduced, and after the treatment is finished, the N in the molten steel is less than or equal to 40 ppm.

In the slab continuous casting production, protective casting is adopted, and the water gap is subjected to argon blowing operation, so that the molten steel is prevented from contacting with air, the increase of oxygen and nitrogen in the molten steel is reduced, and effective boron in the molten steel is protected.

Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: the method comprises the steps of firstly controlling the oxygen content and the nitrogen content of the converter, keeping the oxygen content and the nitrogen content at a lower level, carrying out deep deoxidation and nitrogen treatment on molten steel in an LF (ladle furnace) refining process by designing the adding sequence of Al, Ti and B and the adding amount of Al and Ti, increasing the effective boron content, and reducing the nitrogen content and the oxygen content in the molten steel as much as possible and keeping the effective boron content stable in a subsequent RH (relative humidity) and continuous casting process. According to the invention, the oxygen and nitrogen contents in the molten steel are accurately controlled through the whole process, the generation of acid-insoluble boron is reduced, the effective boron content is increased, the effective boron content (acid-soluble boron/full boron) in the steel billet reaches more than 85%, the problem of low effective boron content of the low-alloy wear-resistant steel is finally solved, and powerful guarantee is provided for subsequent production and final product performance.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments.

Examples 1 to 9

The method for improving the effective boron content in the low-alloy high-strength wear-resistant steel comprises the following steps:

(1) a converter smelting process: carrying out dephosphorization operation, and blowing argon gas from bottom in the whole process, wherein the flow of the argon gas is 200-400 m³H, after one-time-down point oxygen blowing is less than or equal to 500m³Over-blowing is avoided, the slag amount in the tapping process is less than or equal TO 0.25wt%, aluminum blocks and lime are added into a steel ladle for early deoxidation and slagging treatment, TO is less than or equal TO 80ppm, and N is less than or equal TO 30 ppm.

(2) An LF refining procedure: feeding an aluminum wire into a steel ladle by 200-300 m to ensure that the content of acid-soluble aluminum in molten steel is 0.030-0.050 wt%, adding ferrotitanium after the white slag desulfurization is finished, controlling omega (Ti)/omega (N) to be 3-4, blowing argon at the bottom of the steel ladle to keep small-gas soft blowing, and controlling the flow of argon to be 10-20 m³Adding ferrotitanium for 3min, adding ferroboron, adjusting the components and temperature, and blowing argon from the bottom of the steel ladle for more than or equal to 5 min.

(3) RH vacuum treatment process: the total treatment time is more than or equal to 35min, the vacuum degree is less than or equal to 100Pa, the vacuum treatment time is more than or equal to 20min, the pure degassing time is more than or equal to 8min, and the argon net blowing time of the molten steel after RH vacuum treatment is more than or equal to 6 min. After the RH vacuum treatment is finished, the N in the molten steel is less than or equal to 40 ppm.

(4) And a slab continuous casting process: argon is adopted for blowing before pouring of the tundish, a double-layer covering agent is adopted after pouring, argon is blown to protect the pouring by the sealing ring and the long nozzle, the flow of argon is 15-25 NL/min, the depth of the immersion nozzle inserted into the crystallizer is 160-180 mm, and the pouring is carried out at a constant speed.

The effective boron content of the low-alloy high-strength wear-resistant steel is obviously improved through the control of the working procedures, and the effective boron content (acid-soluble boron/full boron) in the steel billet reaches more than 85 percent.

The process parameters of the converter smelting and LF refining processes in the embodiments are shown in Table 1, and the process parameters of the RH vacuum treatment and slab continuous casting processes are shown in Table 2; the effective boron content (acid-soluble boron/total boron) of the billets of the examples after the above-mentioned treatment is shown in Table 2.

Table 1. process parameters of converter smelting, LF refining process.

TABLE 2 technological parameters of RH vacuum treatment and slab continuous casting process

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