Alloy steel and manufacturing method thereof

Abstract

The invention provides an alloy steel and a manufacturing method thereof. The manufacturing method comprises the steps of: primarily smelting steel into molten steel; when the C content of the molten steel is 0.03-0.06 percent, the P content is not more than 0.015 percent and the S content is not more than 0.020 percent, tapping a steel ladle; during tapping, regulating the Si content of the molten steel to be 0.17-0.37 percent, Mn content to be 0.40-0.70 percent, Cr content to be 0.80-1.10 percent and Mo content to be 0.40-0.55 percent, and regulating the oxygen content of the molten steel to be below 0.0020 percent; controlling the Als content of the molten steel to be 0.02-0.0 percent, wherein Als represents acid-soluble aluminium; ensuring that the oxygen content is below 0.0010 percent when the molten steel is refined and the C content of the molten steel is 0.12-0.18 percent after the refining is ended in a steel ladle refining furnace; and carrying out circulating vacuum degassing treatment on the molten steel, and regulating the Ti content of the molten steel to be 0.006-0.010 percent to obtain the alloy steel. The alloy steel comprises the following components in percent by weight: 0.12-0.18 percent of C, 0.17-0.37 percent of Si, 0.40-0.70 percent of Mn, 0.80-1.10 percent of Cr, 0.40-0.55 percent of Mo, 0.006-0.010 percent of Ti, 0.008-0.015 percent of Als and the balance of Fe and unavoidable impurities.

Description

technical field [0001] The invention relates to an alloy steel and a manufacturing method thereof, in particular to an alloy steel which can be used in a high-pressure boiler and a manufacturing method thereof. Background technique [0002] Studies have shown that controlling the Al content of boiler steel in a very low range is the key to the production of boiler steel. The main reason is that high Al content will lead to extremely low yield of post-cold working. However, in general, Al is the more important alloying element in steel. The role of Al is first reflected in the final deoxidation of molten steel, which can keep the equilibrium oxygen of molten steel at a low level and avoid the appearance of high-oxygen steel; secondly, Al is an important fine-grained element, which can improve the strength and toughness of steel; in addition, Al It can also be used to fix nitrogen (N), thereby reducing the aging of steel. The amount of Al added to reflect the above effects i...

AI Technical Summary

Problems solved by technology

This part of nitrogen is fixed by Al, otherwise nitrogen will exist in the steel in the form of free state, which will increase the timeliness of the steel, reduce the impact resistance, and seriously cause premature failure of the steel

[0006] As mentioned above, in the existing 15CrMoG steel production technology, the low Al route should be adopted; however, too low Al content will cause a certain amount of free nitrogen in the steel, which will increase the timeliness of the steel, reduce the impact resistance, and seriously can also cause premature failure of the steel