Low-cost converter steelmaking deoxidization process

[0023] Example 1

[0024] For killed steel (steel grade A36Cr) process steps:

[0025] (1) Open the ladle to the tapping position of the converter, open the bottom blowing system, and the bottom blowing flow rate is 300m 3 /h;

[0026] (2) Shaking furnace releases the steel and starts timing. After 20s tapping, 0.58kg/t of elemental carbon powder is added (0.58kg per ton of steel), and the elemental carbon powder is added within 40S after tapping. In order to better achieve carbon powder deoxidation, the bottom blowing flow rate is reduced to 200m after adding carbon 3 /h, at this time, carbon powder is deoxidized to produce CO gas to participate in the stirring of molten steel. In addition, in order to prevent premature addition of carbon powder causing molten steel to "turn over" and cause safety accidents, the general tapping time is about 7 minutes, so the appropriate time for adding elemental carbon powder is within the time range of 20-60S after tapping to ensure carbon The powder is in full contact with oxygen to improve the deoxidation rate of carbon powder;

[0027] (3) After the carbon powder is added at an interval of 30S, add 1.2kg/t of composite deoxidizer, and all composite deoxidizers will be added within the time range of 80S-140S after tapping. The composition (mass fraction) of the composite deoxidizer is 49.3% silicon, 18.5% calcium, 31.2% barium and 1% aluminum. The time interval between the carbon powder and the composite deoxidizer is an essential element, and its purpose is to react with the oxygen in the steel to prevent the carbon from increasing in the steel.

[0028] After the deoxidizer is added, other alloys can be added according to the requirements of the final product. After the steel is placed, the bottom blowing argon gas is turned off; the ladle is opened to the argon station, and the bottom blowing argon stirring is turned on to make the composition and temperature uniform, and the bottom blowing flow rate 150m 3 /h; After 180s of argon blowing at the argon station, oxygen determination, temperature measurement, and composition sampling, the ladle is moved to the LF refining furnace for refining.

[0029] The timing of the addition of the double deoxidizer in this process is closely related to whether the deoxidation can achieve the effect: the deoxidation method is based on the ratio of 0.17~0.58kg/t within the time period of 20~60S after tapping, first add carbon powder, and stop after the addition of carbon 20~30s, the [C][O] in the ladle will react to generate CO gas to be discharged, which is beneficial to control the carbon increase in the steel <100ppm, avoid adding carbon powder to the reaction and incomplete carbon increase at the same time, the deoxidation amount is the largest, reaching the carbon powder deoxidation The best effect, and the utilization rate of carbon powder deoxidation>50%. In addition, the carbon powder deoxidation product is CO gas, which can be discharged from the molten steel in time without forming new inclusions.

[0030] In this process, the composite deoxidizer (40.5% to 49.5% silicon, 18.5% to 26.0% calcium, 27.0% to 31.5% barium, and 0% to 2% aluminum) is added within 180S in the early stage of tapping. In this process, elementary carbon was used for basic deoxidation before, so the composition and usage of the composite deoxidizer are quite different from the prior art. First of all, the composite deoxidizer in this process design has no iron content and the proportion of aluminum is greatly reduced, even without aluminum. However, the deoxidation of aluminum and iron in the prior art will produce a large amount of aluminum oxide that is difficult to remove. The formation of deoxidation products and MnS, the inclusions are difficult to float up and removed in time and remain in the molten steel, which affects the purity of the molten steel. The use of this process deoxidation method greatly reduces the amount of aluminum iron deoxidizer used, improves the quality of molten steel, and reduces the probability of casting machine flocculation At the same time, reduce the cost of deoxidation and increase profit margins for enterprises. Secondly, the ratio of Si, Ca, and Ba components is more reasonable: alkaline earth metals Ca and Ba have low boiling points and are easy to volatilize loss, while Si can reduce the volatilization loss of Ca and Ba and improve element utilization. CaO-SiO, a deoxidation product of Ca and Si 2. The presence of Ca increases the solubility of Si, and at the same time, Ca can denature and easily remove non-metallic inclusions, and improve the deoxidation utilization rate of Ca and Si. The presence of Ba can improve the deoxidation effect and desulfurization capacity of Ca and Si, and refine the grains. . In addition, the existing composite deoxidizers containing Si, Ca, and Ba are mostly added in an amount of 10-20 kg/t. The reason is that the contact area between the deoxidizer and molten steel is small, and the deoxidized products cannot be dissipated in time, thus affecting deoxidation Therefore, in order to achieve a good deoxidizing effect, the amount of deoxidizer used must be increased, which means that the cost is increased and the purity of the product is decreased. In this process, the carbon powder is used to deoxidize in advance, and useful gas and finely dispersed particles are quickly produced. CO gas enhances the disturbance of molten steel. Under such disturbances, silicon, calcium, and barium can be fully mixed with molten steel, and the deoxidation products continue The rapid rise and absorption of steel, the superposition of chemical and physical effects, give full play to the desulfurization and inclusion denaturation capabilities of calcium and barium, which can effectively reduce the generation of deoxidation impurities and MnS, improve the purity of molten steel, and improve the castability of molten steel. Reduce caster flocculation and improve the quality of cast slabs. In addition, this process has changed the way that traditional deoxidizers are added in the middle and late stages of tapping. Two deoxidizers are added within 20S~180S after tapping to achieve gradient deoxidation and the coordination of chemical reactions and physical disturbances to ensure deoxidation. In terms of the effect, the cost is greatly saved. The specific addition amount of the elemental carbon powder and composite deoxidizer depends on the amount of tapping, so the length of time for addition varies. The pilot test results show that as long as the elemental carbon powder is added within 60S after tapping, all the composite The deoxidizer is added within the 180S time range after tapping, and a complete deoxidizing effect can be achieved. In this embodiment, the elemental carbon powder is added at 40S after tapping, and all the composite deoxidizers are added at 140S.

[0031] Example 2

[0032] For killed steel (steel grade Q345B3) deoxidation process steps:

[0033] (1) Open the ladle to the tapping position of the converter, open the bottom blowing system, and the bottom blowing flow rate is 250m 3 /h;

[0034] (2) Start timing when the steel is put in the shaker, and 0.36kg/t of elemental carbon powder is added after 40s of tapping. After adding carbon, the bottom blowing flow rate is reduced to 150m 3 /h, the elemental carbon powder will be added within 60S after tapping;

[0035] (3) After the carbon powder is added at an interval of 25S, add 1.5kg/t of composite deoxidizer, and all composite deoxidizers are added within the time range of 80S~130S after tapping; the composition (mass fraction) of the composite deoxidizer is 47.5% silicon, 24.5% calcium, 28% barium.

[0036] In this embodiment, the elemental carbon powder is added at 60S after tapping, and all the composite deoxidizers are added at 130S.

[0037] Example 3

[0038] For killed steel (steel grade Q235B2) deoxidation process steps:

[0039] (1) Open the ladle to the tapping position of the converter, open the bottom blowing system, and the bottom blowing flow rate is 200m 3 /h;

[0040] (2) Start timing when the steel is put in the shaking furnace, and start adding 0.17kg/t of elemental carbon powder after tapping 58S. After adding carbon, the bottom blowing flow rate is reduced to 100m 3 /h, the elemental carbon powder will be added within 60S after tapping;

[0041] (3) After adding the carbon powder at an interval of 20S, add 1.8kg/t of composite deoxidizer, and add all composite deoxidizers within 130S~180S after tapping; the composition (mass fraction) of the composite deoxidizer is 44.4% silicon, 25.9% calcium, 27.7% barium and 2% aluminum.

[0042] In this embodiment, the elemental carbon powder is added in 60S after tapping, and all the composite deoxidizer is added in 180S.