A control method for ds inclusions in medium-carbon sulfur-containing aluminum deoxidized non-quenched and tempered steel

Abstract

The invention discloses a method for controlling Ds inclusions in medium-carbon sulfur-containing aluminum deoxidized non-quenched and tempered steel. By adjusting the addition position of S element and optimizing the multi-component composition of refining slag and the composition of molten steel, the oxygen requirement of the product is met. Under the premise, the inclusions are transformed into a solid phase that is easy to float, avoiding the formation of liquid inclusions and CaS, and further optimizing the vacuum treatment time, improving the removal efficiency of inclusions in molten steel, especially large-grained Ds inclusions, reaching To control the effect of Ds inclusions in steel, Ds inclusions in rolled materials can be stably controlled below 0.5 in actual production.

Description

technical field [0001] The invention relates to a method for controlling Ds inclusions in medium-carbon sulfur-containing aluminum deoxidized non-quenched and tempered steel. Background technique [0002] Non-quenched and tempered steel refers to the medium-carbon low-alloy structural steel whose properties are equal to or close to the mechanical properties of quenched and tempered steel by adding microalloying elements to change the phase transformation mechanism of the structure, and through rolling, forging and controlled cooling. Since the non-quenched and tempered steel can omit the quenching and tempering treatment process, compared with quenched and tempered steel, it can greatly save energy and reduce manufacturing costs by about 25%-38%. It is a steel material that is preferentially supported by national policies. And other aspects have been applied, such as automobile engine crankshaft, connecting rod. [0003] In order to ensure the fatigue performance of non-que...

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Problems solved by technology

The high-alkalinity refining slag is not suitable for the production of sulfur-containing steel due to its strong desulfurization performance, and the deoxidation in batches and small batches in the LF refining process will cause the final deoxidized product to be small and difficult to float up and remove, which is not conducive to the reduction of oxygen content; in addition, RH vacuum The processing time and soft blowing time are both longer, which will also lead to an increase in temperature drop, affect the pourability of molten steel, and reduce the production rhythm

[0006] Publication No. CN 101906502 A discloses a calcium treatment method for reducing the size of D-type and Ds-type inclusions in aluminum-containing steel. The calcium treatment is actually adjusted to be carried out after the soft blowing is completed. For sulfur-containing non-quenched and tempered steel, the calcium line The feeding of the feed will form CaS with S in the steel, which will not only affect the castability of molten steel, but also CaS will be attached to calcium aluminate or magnesium aluminum spinel, which will aggravate the level of Ds

[0007] In summary, the existing patents and research are not applicable to the control of Ds inclusions in non-quenched and tempered steels containing sulfur and aluminum. Compared with the control of Ds inclusions in conventional aluminum-containing steels, the difficulty lies in the control of liquid inclusions and CaS It is necessary to balance the requirements of oxygen and sulfur on the basicity of the slag, so it is necessary to explore a new process to reduce the Ds inclusions in the medium-carbon sulfur-containing aluminum deoxidized non-quenched and tempered steel

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