Production process for replacing vanadium-nitrogen alloy with composite vanadium-nitrogen alloy

Abstract

The invention discloses a production process for replacing a vanadium-nitrogen alloy by using a composite vanadium-nitrogen alloy, which is suitable for steel of HRB400 [E] X and has the specification phi of 12-25mm, an original process is kept unchanged in a converter, the composite vanadium-nitrogen alloy is added in a refining furnace to replace part of the vanadium-nitrogen alloy, the composite vanadium-nitrogen alloy is firstly added after molten steel enters a station, the vanadium-nitrogen alloy is added to complement the remaining V component, the refining smelting time is greater than or equal to 20min, and the smelting time is greater than or equal to 20min. The argon blowing time is not less than 4 minutes; the content of V is controlled to be 0.019%-0.023%, the tapping amount is 65 tons or above, the adding amount of composite vanadium and nitrogen is 45 kg, and the remaining components are supplemented with vanadium-nitrogen alloy; the tapping amount is less than 65 tons, the adding amount of the composite vanadium-nitrogen is 40 kg, and the remaining components are supplemented with the vanadium-nitrogen alloy; after rolled steel is rolled, the addition amount of the vanadium-nitrogen alloy is increased or decreased according to the specific value of the mechanical property of the steel, and it is ensured that the mechanical property meets the requirement.

Description

Technical Field

[0001] The invention relates to a production process using a composite vanadium-nitrogen alloy to replace a vanadium-nitrogen alloy. Background Art

[0002] As the main steel material for construction, hot-rolled ribbed steel bars (rebars) are widely used in industrial and civil construction, railways, bridges, highways and other construction projects. In the production process of hot-rolled ribbed steel bars (rebars), in addition to adding a certain amount of silicon-manganese alloy and silicon-ferroalloy to the molten steel, some alloys containing vanadium (V), titanium (Ti), and niobium (Nb) are also added to the micro-alloying process to produce products that meet national standards and use requirements. At present, most steel companies widely use the high-cost vanadium-nitrogen alloy as a micro-alloying alloy in the production process of rebars. The current process method mainly uses the V component in the vanadium-nitrogen alloy to refine the steel grains and increase the toughness. In addition, vanadium and iron can form a continuous solid solution, which strongly reduces the austenite phase area, thereby improving the physical and chemical properties of the steel. Due to the limited N content in the vanadium-nitrogen alloy, the precipitation effect of V after adding it to the steel is not obvious, and the strength performance of the steel cannot be maximized. In addition, the price of vanadium-nitrogen alloy is relatively high. The cost of adding vanadium-nitrogen alloy micro-alloying smelting in the production process of rebars is relatively high. As profits from steel production are getting lower and lower, all steel companies are looking for ways to reduce alloy costs. How to develop alternative additives in rebar production that can both meet national standards and reduce production costs is an important issue facing major steel companies.

[0003] At present, there is no process method to use composite vanadium-nitrogen alloy to reduce alloy cost in rebar production. Many domestic steel mills still use vanadium-nitrogen alloy for micro-alloying, which limits the cost optimization space of rebar. Summary of the invention

[0004] The object of the present invention is to provide a production process using a composite vanadium-nitrogen alloy instead of a vanadium-nitrogen alloy, which can reduce alloy costs and stabilize product performance in the production of threaded steel bars.

[0005] The technical solution adopted by the present invention is a production process using a composite vanadium-nitrogen alloy to replace a vanadium-nitrogen alloy. The applicable steel types are: HRB400[E]X, specification Φ12-25mm, the converter maintains the original process unchanged, the composite vanadium-nitrogen alloy is added in the refining furnace to replace part of the vanadium-nitrogen alloy, the composite vanadium-nitrogen alloy is first added after the molten steel enters the station, and the vanadium-nitrogen alloy is added to make up the remaining V component, the refining and smelting time is ≥20min, and the argon blowing time is ≥4min; the V component is controlled at 0.019%-0.023%, the steel output is more than 65 tons, the amount of composite vanadium-nitrogen added is 45kg, and the remaining components are made up with vanadium-nitrogen alloy; the steel output is less than 65 tons, the amount of composite vanadium-nitrogen added is 40kg, and the remaining components are made up with vanadium-nitrogen alloy; after the steel is rolled, the amount of vanadium-nitrogen alloy added is increased or decreased in proportion according to the specific values ​​of the mechanical properties of the steel to ensure that the mechanical properties meet the requirements.

[0006] In order to reduce the alloy cost of threaded steel bars, the inventor analyzed the method of reducing the alloy cost based on theory, and added a composite vanadium-nitrogen alloy to the molten steel during the production process of threaded steel bars to replace part of the vanadium-nitrogen alloy. Since the N content of the composite vanadium-nitrogen alloy is enhanced, V can be better precipitated and crystallized in the steel, which plays a role in refining the grains. Therefore, under the condition of the same V content in the molten steel, the strength of the steel will be enhanced, the strengthening effect in the steel will be promoted, the strength of the steel will be improved, and the control range of the V component in the steel will be reduced. In addition, the price of the composite vanadium-nitrogen alloy is much lower than that of the vanadium-nitrogen alloy, which has excellent utilization space for reducing alloy costs and stabilizing product performance in the production of threaded steel bars, and is an effective and operable process method.

[0007] (1) Based on the characteristics of high [N] content in composite vanadium-nitrogen alloys and the importance of [N] content in vanadium-nitrogen alloys in improving steel strength and reducing the amount of microalloying elements used, the inventors first theoretically analyzed that composite vanadium-nitrogen alloys can maximize the [N] concentration in steel. The higher the [N] concentration in steel, the more V (C, N) precipitates during rolling. The use of composite vanadium-nitrogen alloys can effectively promote the strengthening effect in steel and improve the strength of steel.

[0008] (2) In vanadium-nitrogen alloys, V can form compounds with both C and N, and the precipitates are VC and VN. The affinity of V with N is greater than that of V with C, that is, VN is generated first, followed by VC. When V / N reaches the ideal chemical ratio (V:N=3.64:1), vanadium can precipitate to the greatest extent. When the steel contains an appropriate amount of V element, nitrogen addition can reduce the particle size of V, and the increase in the number of fine and dispersed V precipitation phases can significantly improve the strength of threaded steel bars. In the vanadium-nitrogen alloy V:N=5.5:1, the N content is obviously insufficient, which affects the precipitation and crystallization of V in molten steel. In the composite vanadium-nitrogen alloy V / N=1.13:1, the N content is enhanced, which can enable vanadium to precipitate and crystallize better in steel, playing a role in refining grains, so that under the same V content in molten steel, the strength performance of steel will be enhanced.

[0009] (3) During the smelting process of threaded steel bars, a composite vanadium-nitrogen alloy is added to the ladle to replace part of the vanadium-nitrogen alloy. Under the condition of the same V content in the molten steel, the strength of the steel will be enhanced. In addition, the process of using a composite vanadium-nitrogen alloy to replace part of the vanadium-nitrogen alloy can optimize the V content control range in the production process of threaded steel bars, reduce the alloy consumption cost, and achieve the purpose of reducing costs and increasing efficiency.

[0010] ; ; ; Through experiments, the composite vanadium-nitrogen alloy was used to replace part of the vanadium-nitrogen alloy, and the finished product [V] was 0.021%. The mechanical performance indicators of the rolled HRB400EX Φ12, Φ14, Φ22, Φ18, and Φ25 specifications all met the national standard requirements, among which the average yield strength was 461.6Mpa. Compared with the cost of HRB400E specifications Φ12-25 without the composite vanadium-nitrogen alloy, the alloy cost savings were: 62.9-58.297=4.603 yuan / t steel. Effect of the implementation of the invention: Using the composite vanadium-nitrogen alloy to replace part of the vanadium-nitrogen alloy in the production process of threaded steel bars can ensure the stability of the strength performance of the steel, reduce the alloy cost, and achieve the purpose of reducing costs and increasing efficiency. According to the calculation of saving 4.603 yuan per ton of steel, a steel plant with an annual output of 1 million tons of molten steel threaded steel bars will have an annual benefit of 1,000,000×4.603=4.603 million yuan after applying this process method. The present invention starts from production practice and designs a new process that can effectively reduce the alloy consumption cost in the production process of threaded steel bars, achieve the purpose of reducing costs and increasing efficiency, and explore an effective process method for deeply reducing the production cost of threaded steel bars, with remarkable results. Implementation

[0011] A production process using a composite vanadium-nitrogen alloy instead of a vanadium-nitrogen alloy, the process implementation steps of the present invention are as follows: (1) The converter maintains the original process unchanged. After the converter taps steel, the ladle is hoisted to the refining furnace; (2) After the ladle car is driven to the smelting station, the composite vanadium-nitrogen alloy is added into the ladle; (3) After taking the interim sample, add vanadium-nitrogen alloy according to the V component of the interim sample to increase the V component to the range required by the process; (4) After smelting in the refining furnace, soft blowing is carried out, and the soft blowing time is ≥ 4 minutes; (5) After continuous casting, the ingot is sent to the steel rolling mill for rolling. Example

[0012] (1) Applicable steel types: HRB400 (E) X (specification Φ12-25mm). The converter maintains the original process unchanged, and the composite vanadium-nitrogen alloy is added in the refining furnace to replace part of the vanadium-nitrogen alloy. After the molten steel enters the station, the composite vanadium-nitrogen alloy is first added, and the vanadium-nitrogen alloy is added to make up the remaining V component. The refining and smelting time is ≥20min, and the argon blowing time is ≥4min.

[0013] (2) The V content is controlled at 0.019%-0.023%. When the steel output is above 65 tons, the amount of composite vanadium and nitrogen added is 45 kg, and the remaining components are supplemented by vanadium-nitrogen alloy; when the steel output is below 65 tons, the amount of composite vanadium and nitrogen added is 40 kg, and the remaining components are supplemented by vanadium-nitrogen alloy.

[0014] (3) After the steel is rolled, the amount of vanadium-nitrogen alloy added is increased or decreased in proportion to the specific values ​​of the mechanical properties of the steel to ensure that the mechanical properties meet the requirements.

Claims

1. A production process using a composite vanadium-nitrogen alloy instead of a vanadium-nitrogen alloy, characterized in that Applicable steel types are: HRB400[E]X, specification Φ12-25mm, the converter maintains the original process unchanged, the composite vanadium nitrogen alloy is added in the refining furnace to replace part of the vanadium nitrogen alloy, the composite vanadium nitrogen alloy is added first after the molten steel enters the station, and the vanadium nitrogen alloy is added to make up the remaining V component, the refining and smelting time is ≥20min, and the argon blowing time is ≥4min; the V component is controlled at 0.019%-0.023%, the steel output is more than 65 tons, the amount of composite vanadium nitrogen added is 45kg, and the remaining components are made up with vanadium nitrogen alloy; the steel output is less than 65 tons, the amount of composite vanadium nitrogen added is 40kg, and the remaining components are made up with vanadium nitrogen alloy; after rolling, the amount of vanadium nitrogen alloy added is increased or decreased in proportion according to the specific values ​​of the mechanical properties of the steel to ensure that the mechanical properties meet the requirements.