Manufacturing process of soft martensitic stainless steel valve box forging

Abstract

The invention relates to a manufacturing process of a stainless steel valve box forging. The stainless steel valve box forging is manufactured by adopting low-carbon (preferential ultralow-carbon) soft martensitic stainless steel, and comprises the following chemical components (wt%): C not more than 0.06, Si not more than 0.80, Mn not more than 1.0, P not more than 0.015, S not more than 0.010, 12-16 of Cr, 3.5-6.0 of Ni, Mo not more than 1.0, 0.01-0.02 of N, Cu not more than 0.010, and 0.01-0.015 of Al. The process comprises the steps of forging, annealing after forging, flaw detection afterrough machining, solid solution treatment, tempering, and sampling detection. In heating of the forging and the solid solution treatment, a gradient heating mode is adopted. After preheating, a higher heating speed is adopted to reach higher overheating degree to obtain finer austenite grains; through multi-directional forging and increment of a forging ratio, a forging material is more compact,and the mechanical performances are non-directional; and the solid solution treatment and the tempering treatment are combined to control a proper amount of reversed austenite to disperse among martensitic laths or substructures. The manufactured valve box forging is high in comprehensive and mechanical performances, wear resistance and corrosion fatigue limit resistance, and is excellent in coldand hot working performances.

Description

Technical field [0001] The invention relates to a stainless steel valve box forging, in particular to a soft martensitic stainless steel valve box forging and a manufacturing process thereof. Background technique [0002] The fracturing pumps used in shale oil and gas exploitation are under harsh working conditions. Their valve boxes are subjected to high pressure and alternating stress, and are also exposed to corrosion and abrasion of acid media and sand. This requires that the materials used to manufacture the valve boxes must be corrosion resistant and have high Toughness. At present, Cr-Ni-Mo-V alloy steel is mainly used, and the tempered sorbite structure is obtained by quenching and high temperature tempering to achieve high comprehensive mechanical properties. However, due to the large valve box forgings, the components in the forgings are segregated seriously, and band-like structures or serious mixed crystals often appear. When subjected to large external forces, the u...

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Problems solved by technology

At the same time, a layer of Cu-rich alloy will be enriched under the surface oxide skin of the steel. The melting point of this Cu-rich alloy is lower than 1100°C. During hot working, this Cu-rich alloy layer will melt and invade the surface grain boundary of the steel, making the steel Severe cracking often occurs during hot processing, resulting in low yield and increased manufacturing costs

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