Nonmagnetic Strength-toughen stainless steel and method for manufacturing same

Abstract

The invention provides a non-magnetic strengthening and toughening stainless steel and a manufacturing method thereof. The non-magnetic strengthening and toughening stainless steel comprises the following mechanical components by weight percentage: C, less than or equal to 0.12 percent; Si, less than or equal to 1.5 percent; Mn, 14.5 to 16.5 percent; S, less than or equal to 0.010 percent; P, less than or equal to 0.030 percent; Cr, 15.1 to 16.0 percent; Ni, less than or equal to 0.90 percent; Mo, less than or equal to 0.70 percent; Nb, less than or equal to 0.35 percent; N, 0.25 to 0.50 percent; the rest, Fe and inevitable impurity elements. The non-magnetic strengthening and toughening stainless steel of the invention is made of the steels by the smelting process of electric furnace and refining as well as large deformation forging process at ultra low temperature. The non-magnetic strengthening and toughening stainless steel has the advantages of low cost material, simple production process, stable non-magnetism and processing hardening coefficient, stronger anti-corrosion performance and above 90 percent of qualified rate of intercrystalline corrosion resistance so as to meet the operating requirements of the steel used for a petroleum non-magnetic drill collar.

Description

technical field [0001] The invention relates to the technical field of smelting engineering, in particular to stainless steel materials, and more specifically to a non-magnetic toughened stainless steel and a manufacturing method thereof. Background technique [0002] Affected by the global energy crisis, oil drilling and development at home and abroad are developing in the direction of refinement, economy, and depth. The number of drilling wells used for oil extraction has increased sharply, and the demand for steel used in oil drilling has also increased. According to the classification of the magnetic function of steel, the steel used in petroleum drills can generally be divided into magnetic steel (general purpose) and non-magnetic steel (special purpose, such as materials for sensor protection devices). [0003] The non-magnetic steel must be fully austenitic, and must have a Cr content of more than 12%. The non-magnetic steel used in oil drills is mainly 200 and 300 se...

AI Technical Summary

Problems solved by technology

[0005] There are two types of steel used in foreign oil drilling and production: one type develops in the direction of high chromium and high nitrogen, and its purpose is to strive for higher strength, hardness index, and improve corrosion resistance; the other type develops in the direction of chromium-nickel- The development of molybdenum-nitrogen series has the advantages of stronger corrosion resistance and longer service life, but the disadvantages of increased cost and low processing hardening coefficient

[0006] The non-magnetic steel used in domestic production of oil drill collars is mainly N1310 non-magnetic steel jointly developed by Fugang, the Institute of Metal Research of the Chinese Academy of Sciences and the Liaohe Oilfield Drilling and Production Research Institute. It is a research project based on European technology and has obtained a national invention patent (Invention name: high-strength non-magnetic drill collar steel; patent number: 93115802.8; authorized announcement number: CN1038353C), currently only Zhongyuan Special Steel is producing similar N1310 non-magnetic steel in batches in China, and its production capacity is far from meeting market demand

The high-strength non-magnetic drill collar steel, that is, N1310 non-magnetic steel, although its mechanical properties have reached the standards issued by the International Ministry of Petroleum, it still has the following deficiencies: (1) The corrosion resistance of the steel is poor, and the main technical indicators—— The qualified rate of resistance to intergranular corrosion is only 50%; (2) the composition, performance, and shape of the product are not stable enough to meet the requirements of use; (3) the content of Ni and Mo precious metals is relatively large, resulting in high raw material costs; (4) ) The production process of steel adopts the dual smelting process of "electric furnace + refining + electroslag remelting", which leads to high production costs

At present, most of the non-magnetic steel for oil drill collars is imported, and a small part is produced domestically. However, domestic billet suppliers have problems such as insufficient smelting capacity, limited output, unstable billet quality, and high sales prices.

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