Manufacturing process of X80 steel grade type DN1400 thick-wall tee

Abstract

The invention relates to a manufacturing process of an X80 steel grade type DN1400 thick-wall tee. The manufacturing process comprises the following steps: preparing a base material steel tube; performing flaw inspection; performing finite element design for a bulging die; carrying out hot extrusion process; carrying out thermal treatment process; performing the flaw inspection again. With the adoption of the manufacturing process, tee tubes with high steel grade, large aperture and large wall thickness can be manufactured successfully; in addition, the tubes are high in strength, high in impact toughness, and high in resistance to low-temperature facture, and the actual demand on natural gas transportation can be met.

Description

technical field [0001] The invention relates to a manufacturing process of a tee, in particular to a manufacturing process of an X80 steel grade DN1400 thick-walled tee. Background technique [0002] Tee is one of the key products of pipeline engineering construction, and it plays an important role as a "bridge" in oil and gas transportation. With the successive start of domestic and foreign pipeline projects in recent years, the demand for tee has increased sharply. my country has mastered a mature theoretical basis and stable manufacturing process for low steel grade and small diameter tees. Most pipe fitting manufacturers still use small diameter and low steel grade tees as their main products. However, with the continuous improvement of oil and gas demand in my country, oil and gas pipelines are developing in the direction of high pressure, high strength and large diameter. The pipe with a diameter of 1422mm is built, so there must be a tee fitting used with it. However,...

AI Technical Summary

Problems solved by technology

For small-diameter pipes, it is relatively easy to meet their low-temperature fracture resistance, but for large-diameter, thick-walled pipe fittings, it is difficult to process them. The requirements are higher. In the process of processing, we must pay close attention to the change of process conditions on the properties of steel. In the process of process research, we need to go through trials, tests, and supplemented by finished product inspection to verify the rationality of the process, which requires more research efforts.

[0004] Large-caliber tees are usually produced by welding, casting, and hot extrusion, each has its own advantages and disadvantages. The advantage of the tee produced by welding and casting methods is that it can obtain tee fittings with complex shapes, but the toughness of the weld seam for the welding method Low, can not withstand large stress, poor seismic performance, not suitable for natural gas pipelines, for casting methods, coarse grain structure, poor mechanical properties of pipe fittings, not suitable for natural gas pipelines that need to withstand high pressure

At present, the popular method of forming tee pipe fittings is hot extrusion molding, but the hot extrusion molding process is more complicated, and the number of processing steps determines the number of influencing factors. In order to obtain the desired performance, it is necessary to comprehensively consider the properties of the steel itself and the shape of the molding die. Selection, selection of heat treatment process, etc., and need to be verified by appropriate inspection and testing methods. At present, there is no mature thermoforming process with such a large nominal diameter as DN1400 for reference.