A 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 the exploitation of shale oil and gas have harsh working conditions, and their valve boxes are subjected to high pressure, alternating stress, and are also exposed to corrosion and wear of acid media and sand. toughness. At present, Cr-Ni-Mo-V alloy steel is mainly used to obtain tempered sorbite structure through quenching + high temperature tempering to achieve high comprehensive mechanical properties. However, due to the large valve box forgings, the composition segregation in the forgings is serious, and banded structures or serious mixed crystals often appear. When a large external force is applied, the uneven deformation will cause a large internal stress, which is easy to cause corrosion. Failure due to fatigue cracks, ...

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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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