High-performance hydrogen sulfide corrosion resistant oil drill rocker and its heat treatment process

Abstract

The present invention relates to a high-performance hydrogen sulfide corrosion resistant petroleum drill pipe with a weight percentage of components as follows: C 0.20-0.32 percent, Si 0.1-0.5 percent, Mn 1.0-1.5 percent, Cr 0.5-1.5 percent, Mo 0.8-1.2 percent, P less than or equal to 0.015 percent, S less than or equal to 0.01 percent and the remainders are Fe and unavoidable impurities. The drill pipe of the present invention has a higher content of Mn, which can guarantee an upset end with a thickness of over 30mms to be fully hardened, thereby guaranteeing the sulfur-resistant performance of the upset end. The drill pipe of the present invention has a higher content of Mo, which can improve the backfire-preventive stability of the material, thereby raising the backfire temperature, reducing the residual stress and guaranteeing the sulfur-resistant performance. Simultaneously, the invention can make the pipe body with a different wall thickness and the upset end have the same cooling speed by controlling the outer water injection of the upset end and pipe body of the steel pipe, reducing the water injection outside the pipe body or increasing the water injection outside the upset end of the drill pipe, to ensure that the pipe body and the upset end have the same quenching structure, and the same mechanical property can be achieved after the backfire.

Description

technical field [0001] The invention relates to a hydrogen sulfide corrosion-resistant petroleum drill pipe and its heat treatment process. The hydrogen sulfide corrosion-resistant petroleum drill pipe processed by the heat treatment process designed in the present invention has a yield strength of steel grade above 105 ksi. Background technique [0002] The traditional main process of producing sulfur-resistant drill pipe is: thicken the two ends of the hot-rolled seamless steel pipe according to the required size, and then perform overall quenching and tempering heat treatment to make a qualified drill pipe body. After the heat-treated tool joint and the drill pipe body are connected by friction butt welding, the weld seam is heat treated, and finally the oil drill pipe is made by proper machining. [0003] For the drill pipe body, in order to ensure the strength after butt welding with the tool joint, the pipe end must be upset and thickened before being welded with the t...

AI Technical Summary

Problems solved by technology

In order to ensure the hardening of the thickened end of the drill pipe, higher C, Mn, and Cr should be added. However, due to the thinner pipe body, the hardenability is too high and it is easy to be quenched. Therefore, the hardenability should be appropriately reduced.

The problem caused by the reduction of hardenability is that the number of quenched martensite at the thickened end of the drill pipe with a thickness of 30 mm is reduced, and the uniformity of the tempered structure is reduced, which seriously affects the sulfur resistance of the pipe end

Therefore, it can be seen from the above table that for the product with the grade SS105 in Table 1, the hardenability of the product is obviously insufficient due to the low Mn content; at the same time, the low Mo content causes poor tempering stability, which ultimately affects sulfur resistance

For Grant’s grade DP105 in Table 1, the content of Mn and Mo is relatively high. Although the hardenability is very good and the sulfur resistance is also good, but in the case of hardening at the thickened end, the pipe body is easy to Cracks appear