Method for manufacturing composite elbow with anticorrosion function

Abstract

The invention relates to a method for manufacturing a composite elbow with an anticorrosion function, which comprises the following steps of: (1) manufacturing an elbow inner layer by machining a seamless stainless steel pipe in a bending way; (2) dividing an elbow outer layer into two symmetrical parts along the central line of inner and outer arcs, and performing hot-pressing molding on the two parts by using pipeline steel plates respectively; (3) assembling together the two hot-pressed molded parts of the elbow outer layer and the elbow inner layer, and connecting together the two parts of the outer layer in a welding way; and (4) tightly combining the stainless steel elbow inner layer and the pipeline steel outer layer in an expanded joint way. Compared with an all-stainless steel elbow, the elbow comprising the elbow outer layer made from the pipeline steel can effectively control the manufacturing cost; through the method of molding the inner and outer layers of the composite elbow respectively and then compositing the inner and outer layers, the problem of hot-working and molding difficulty caused by the direct adoption of a composite material is effectively solved, so the method is applied to the manufacture of the composite elbow with a relatively larger caliber and a relatively larger wall thickness; and the elbow can be used for H2S medium-containing oil and gas conveying pipelines to improve the conveyance capability and safety of the pipelines.

Description

technical field [0001] The invention belongs to the field of mechanical product manufacturing, and relates to a method for manufacturing a composite elbow of stainless steel and pipeline steel that can be applied to oil and gas transportation pipelines. Background technique [0002] Pipelines are an important way of oil and gas transportation. Elbows are common pipe fittings in pipelines. Due to their special structure, for medium and high pressure pipelines, in order to ensure safety, the design wall thickness of elbows is usually larger than that of steel pipes for pipelines. For hydrogen sulfide (H 2 S) in oil and gas fields, the transmission medium is corrosive to the pipeline, and the material used for the pipeline is required to have the ability to resist hydrogen-induced cracking (HIC) and sulfide stress corrosion cracking (SSCC). [0003] In order to reduce the cracking probability of elbows in H2S medium, materials with strong corrosion resistance should be used to...

AI Technical Summary

Problems solved by technology

However, the cold forming ability and application range are limited. For large-diameter thick-walled elbows used in oil and gas pipelines, thermal processing is often required during the elbow forming process, which brings difficulties to the direct use of composite materials to manufacture elbows.

First, the thermal processing temperature of stainless steel and pipeline steel is inconsistent. During the forming process of pipeline steel, the heating temperature of 800℃~900℃ is often used, and in order to ensure the performance, tempering treatment of 400℃~650℃ is often used. For stainless steel materials, The sensitization temperature range is between 450°C and 850°C, so it is difficult to use the same thermal processing process for the two materials

Second, the ductility of stainless steel and pipeline steel is different, and the deformation ability is not coordinated in the heated state, which is not conducive to the forming of elbows

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