Fine-grain ferrite + pearlite type N80-1 non-quenched and tempered seamless oil bushing, and production method thereof

Abstract

The invention relates to a fine-grain ferrite + pearlite type N80-1 non-quenched and tempered seamless oil bushing. The components of the oil bushing comprise 0.35-0.40mass% of C, 0.20-0.35mass% of Si, 1.55-1.75mass% of Mn, 0.020mass% or less of P, 0.010mass% or less of S, 0.20mass% or less of Cu, 0.10mass% or less of Ni, 0.30mass% or less of Cr, 0.05mass% or less of Mo, 0.105-0.145mass% of V, 0.02mass% or less of Nb, 0.005-0.025mass% of Ti, 0.0085-0.0140mass% of N, and the balance Fe and inevitable impurities, wherein the sum of the mass percentages of As, Sn, Pb, Sb and Bi is not greater than 0.050%. A production method of the oil bushing comprises a step of blank material heating, a step of perforating, a step of tube rolling, a step of phase transition recrystallization and temperature-controlled crude tube cooling to 500DEG C or less, a step of reheating for controlling the furnace temperature in a range of 900-950DEG C, a step of sizing or reducing, and a step of air cooling. The method avoids the large maneuverability difficulty of the control of the steel tube deformation parameters and the cooling speed, effectively controls the phase transition recrystallization and the reheating furnace temperature through the reasonable matching and addition of alloy elements, and refines and improves the structure through fully utilizing the carbonitride precipitating effect of V in austenite in order to improve the toughness without reducing or substantially reducing the strength.

Description

technical field [0001] The invention relates to an N80-1 non-quenched and tempered seamless oil casing and a production method thereof, in particular to a fine-grain ferrite+pearlite type N80-1 non-quenched and tempered seamless oil casing and a production method thereof. Background technique [0002] N80-1 non-quenched and tempered seamless oil casing is the highest non-quenched and tempered steel grade product in the API 5CT standard, with high strength requirements (yield: 552-758MPa, tensile ≥ 689MPa), usually by adding an appropriate amount of alloy elements Mn, Cr, Mo and a small amount of microalloying elements V, Nb, Ti, and control the hot rolling parameters to replace quenching and tempering treatment to meet high strength requirements. This production method greatly reduces production costs and simplifies production. process and is widely used. At present, there are more than 20 commonly used steel types for this product in China: 27Mn2V, 34Mn2V, 36Mn2V, 36Mn2VNb...

AI Technical Summary

Problems solved by technology

In order to meet the high-strength requirements of this product, the addition of alloying elements Mn, Cr, Mo, V, Nb, and Ti can significantly improve the strength, but also significantly improve the hardenability of the material. In addition, the seamless steel pipe The hot rolling and cooling process parameters of the steel plate cannot be strictly controlled like that of the plate, so that the structure of the final product is often coarse and even contains part of the bainite or martensite structure, which sharply reduces the toughness of the product, and the main addition of microalloying elements V is more Precipitation in ferrite or even pearlite during cooling, although the strengthening effect is significant, it does not play a role in improving the structure and refining the grain

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