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Discussion and practice on factors affecting steel material consumption

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This article conducts a detailed analysis of the factors affecting steel material consumption. By improving the structure of the charging materials, optimizing the slag-making process, reducing the converter splash rate, and strengthening the recovery of internal iron-containing resources, the converter molten steel recovery rate was effectively increased and the consumption of steel materials was reduced.

In today’s steel industry, competition is intensifying, and profit margins are under severe pressure. To confront market challenges effectively, cost reduction and efficiency enhancement measures are imperative. Converter steelmaking accounts for over 70% of production costs, with steel quality directly reflecting a plant’s technical and managerial competence. This directly impacts competitiveness and operational success, making reduction in steel consumption a critical priority for steelmaking enterprises.

This article provides a comprehensive analysis of the converter line at Lianyang Iron and Steel Co., Ltd.’s No. 1 Refining and Rolling Plant. It identifies specific improvement opportunities tailored to current production realities. These targeted measures aim to significantly reduce steel consumption, thereby enhancing operational efficiency and cost-effectiveness.

By implementing these measures, substantial progress has been achieved in curbing steel material consumption. This not only strengthens the plant’s competitive edge but also underscores its commitment to sustainable operational excellence in a challenging market environment.

Steelmaking line production status

The converter line of the No. 1 refining and rolling plant currently has three oxygen top-bottom combined blowing converters with a nominal capacity of 100t, one molten iron pretreatment, three argon blowing stations, and two 6-machine and 6-stream arc continuous casting machines. Annual steel production is 3.9 million tons. The main varieties include HRB series, CSP low carbon steel, CSP plain carbon steel, low carbon alloy steel, high carbon high strength steel and other new steel types.

Steel material consumption calculation caliber and current situation

Calculation method of steel material consumption

Steel material consumption (kg/t) = steel material entering the furnace (kg) ÷ qualified steel output (t);

Steel material consumption (t) = molten iron amount (t) + pig iron amount (t) + scrap steel amount (t) + ore (t);

Scrap steel is divided into purchased scrap steel and self-produced scrap steel from the source. Pig iron is added because the steelmaking capacity is greater than the blast furnace production capacity and the amount of molten iron is insufficient. Pig iron blocks are purchased to maximize the converter production capacity.

Current situation of steel material consumption

In 2016, the physical consumption of steel materials in the first refining and rolling mill was 1079.31kg/t, which was significantly better than in previous years.

 Main factors affecting steel material consumption

The #6 blast furnace of Lianyang Iron and Steel Co., Ltd. is in the late stage of furnace service. The quality of the molten iron is poor. The amount, temperature and composition of the molten iron slag entering the furnace fluctuate greatly. The volume ratio of the converter is small. It is greatly affected by the quality of the raw materials entering the furnace and the structure of the charging materials. The converter smelting process is prone to splashing, the splashed slag has a large iron content, high flux consumption, high final slag TFe, poor end temperature and composition control, resulting in more returns and interrupted continuous casting, and serious overblowing and high temperature phenomena; The stability of the casting operation is poor and the excess molten steel is lost, which seriously affects the reduction of steel material consumption.

Optimization and improvement measures to reduce steel material consumption

Optimize the structure of the charging materials and implement a loading system based on steel types

Optimizing the structure of the charged steel materials has two main meanings. The first is to propose the optimal steel material structure based on the cost-effectiveness calculation of the steel materials to stabilize the weight of the charged steel materials. After calculating the heat balance of the converter and combining it with practical experience, major improvements were made to the original charging system and the structure of the charging materials.

First, adjust the structure of the charging materials, and through detailed cost accounting, it is proposed to reduce high-priced scrap steel as cold materials, and use the heat of reorganization in the molten iron to add more low-priced cold materials such as iron ore to reduce costs.

Secondly, improve the loading system, because the ore used in the converter for steelmaking will have a certain impact on splashing, output, environmental protection, furnace conditions, etc. In order to improve the operating conditions of the converter, it was decided to reduce the charging amount of the converter and relatively increase the reasonable furnace volume ratio to lay a good foundation for the converter operation. The lower scrap steel ratio made the heat in the furnace surplus, creating favorable conditions for adding low-priced ore. The addition of ore promotes the rapid melting of lime into slag, improves the utilization rate of lime, and lays the foundation for reducing lime consumption.

Different steel types have different smelting end-point requirements. Formulating different ratios of molten iron and scrap steel according to different steel types is helpful to accurately hit the end-point composition and temperature and reduce blow loss during the smelting process.

It can be seen from the test data, as shown in Table 1, that with the increase in molten iron consumption, the total charging amount remains unchanged. By adjusting the ore addition

The amount (adjusted according to the physical heat of molten iron, Si content and smelting end temperature control conditions), the metal yield is increased, and the consumption of steel materials is significantly reduced.

Table 1 Consumption of steel materials under different furnace charging structures

Planmolten iron;tpig iron;tscrap steel;tMolten iron;kg/tPig iron;kg/tScrap steel;kg/tOre;kg/tSteel material consumption;kg/t
195015957.780.00130.693.151081.62
296014965.250.00120.404.821080.46
397013972.680.00110.166.471079.32
498012980.080.0099.988.121078.18

Optimize the slagging process and reduce lime consumption

Lime is the main raw material for converter slag making. The process of melting lime into slag requires a large amount of FeO and heat. A large amount of lime will inevitably increase the cost of steel materials. Therefore, a refining and rolling mill made the following optimizations to the slagging system.

Control of lime addition amount

In order to accurately control the amount of lime added to the converter and avoid unnecessary waste and quality and cost fluctuations caused by insufficient addition, we must first strengthen the maintenance and inspection of metering equipment to improve metering accuracy. Secondly, a corresponding static mathematical calculation model was established based on the composition and temperature of the molten iron entering the furnace, as well as the composition and temperature of different steel end points, which effectively avoided waste of lime and insufficient addition.

Limestone steelmaking and less slag steelmaking

Since ore added to the converter is prone to splashing, in order to balance the smelting heat of the converter, the amount of ore added should be appropriately reduced to control splashing and reduce production costs. Through continuous exploration, the feasibility of using limestone to make steel in the first refining and rolling mill was verified, and the purpose of reducing the cost of converter steelmaking was achieved. The physical and chemical indicators of limestone are shown in Table 2.

Table 2 Physical and chemical indicators of limestone

Granularity rangeCaOSiO2PS
10~30mm≥52%≤2%≤0.04%≤0.04%

With improved hot metal conditions, Lianyang Iron and Steel Co., Ltd. No. 1 Refining and Rolling Plant reduced lime based on hot metal composition. Average slag alkalinity decreased, lowering converter slag and steel material consumption. In 2016, flux structure optimization reduced lime consumption by 11.49kg/t compared to 2015. Total flux consumption dropped by 8.24kg/t, cutting steel material and flux costs significantly (refer to Table 3).

Table 3 Comparison of lime consumption and total flux consumption in two years

monthlime;kg/tFlux;kg/t 
2015201620152016
145.1130.1362.2861.41
247.3630.5966.3058.55
346.8327.0064.9748.10
443.3827.6562.9049.56
545.4427.6564.8751.06
645.7025.3964.5150.90
745.9727.7265.2249.78
845.1427.9963.0853.75
934.5830.1055.2850.96
1031.7333.9656.5952.60
1131.3935.6554.8954.11
1231.1137.2250.2659.52
all41.4529.9661.4453.20

Control of TFe in slag

The amount of converter slag is calculated based on 80kg. For every 1% increase in converter final slag TFe, steel material consumption will increase by 0.42kg/t steel. Therefore, reducing the TFe content of converter final slag is beneficial to reducing steel material consumption. To this end, by increasing the carbon pulling rate at the end of the converter (C ≥ 0.08%), reducing the number of post-blow and over-blow heats in the converter, and ensuring the end-point lance pressing time (the corresponding lance pressing time is determined according to different steel types), the entire blowing process can be ensured. On the premise of processing good slag, the TFe content of the final converter slag has been effectively reduced. The situation in the past two years is shown in Table 4.

Table 4 Converter end-point carbon pulling rate (C≥0.08%) and final slag

20152016
Carbon pulling rate; %TFe;%Carbon pulling rate; %TFe;%
68.5611.9577.9311.60

 Reduce converter splash and reduce the amount of scattered slag under the furnace

Splash is a phenomenon that is difficult to avoid in the converter production process. Since splash contains a large amount of metal, the more violent the splash, the higher the consumption of steel materials. Factors influencing converter splashing include furnace volume ratio, charge structure, and molten iron silicon content. Measures refine operations and management to prevent splashing and slag scattering comprehensively.The improvement in quantity is shown in Table 5.

Table 5 Amount of loose slag under converter furnace

Bulk slag volume in 2015; kg/tBulk slag volume in 2016; kg/t
40.5427.43

Strengthen internal management and reduce the loss of iron-containing resources

Recycling focuses on iron-containing resources like loose furnace slag, slag trays/cans, and ladle rims. Improved management and specific regulations have effectively reduced resource loss and minimized steel material consumption. Table 6 illustrates the recycling outcomes.

Table 6 Iron-containing resource recovery

20152016
Furnace bottom slag recovery ratioOther iron-containing resourcesFurnace bottom slag recovery ratioOther iron-containing resources
39.52% 6.43kg/t steel50.71%8.06kg/t steel 

Application effects

Through the above-mentioned technical improvements and management, the flux consumption of Lianyuan Iron and Steel Co., Ltd. No. 1 Refining and Rolling Plant has been continuously reduced, the converter process control has become more controlled, and production has gone more smoothly. With the improvement of various indicators, the consumption of steel materials has been significantly reduced. The consumption of steel materials is shown in the table 7.

Table 7 Steel material consumption control situation

Steel material consumption in 2015; kg/tSteel material consumption in 2016; kg/t
1098.031079.31

Conclusion

There are many factors that affect the consumption of steel materials. This article integrates refining and rolling mill production practices to optimize processes and enhance internal management. Key areas include converter loading, slag formation, and final slag TeO control.What time is it:

a. Precise steel material calculation and refined management guide efforts to reduce consumption effectively.

b. Promote standardized operations and unify the converter shaking operation mode to create good conditions for the improvement of various indicators.

c. Improve the measurement accuracy of various materials, making it possible to scientifically reduce the consumption of steel materials.

d. Reducing steel material consumption is a systematic project. Efforts include optimizing operations, enhancing management, lowering tapping temperature, extending tundish life, and reducing casting accidents.

LMM YOTAI established in 2007. Our production technology comes from Japanese Yotai. As an experienced and international player in the refractories industry. We have succeeded in expanding both the breadth of its product range and the depth of its services. From raw material selection, refractory portofio & optimization, installation & services & recycle of used refractories on site to further reduce client’s Opex & Capex in refractory consumption per ton steel output, meanwhile improve product quality of client.

Our Product have been supplied to world’s top steel manufacturer Arcelormittal, TATA Steel, EZZ steel etc. We do OEM for Concast and Danieli for a long time

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