What might effect the use of stainless steel pipe fittings?

China is a major country in demand for stainless steel pipelines, and the future market is huge. According to the 2013 statistics, there are about 160 billion water supply pipelines of construction in the country. At present, the market demand for thin-walled stainless steel water supply pipelines is only more than 3 billion. The market penetration rate of stainless steel pipelines is still very low in China, while the penetration rate of stainless steel water supply pipelines in the United States, Germany, and Japan is all above 80%. In the future, China's stainless steel pipeline market will have a rapid development, how to deal with the development? This article mainly introduces the factors that affect the performance and service life of stainless steel pipe fittings.

1. The influence of material on the service life of pipe fittings

The main difference between stainless steel material 304 and 304L is that: 304 contains C (carbon) content ≤0.08%, and 304L contains C content ≤0.03%. The content of NI (nickel) in 316 material is 1% -2% higher than that of 304L. It mainly reduces the Cr (chromium) content and increases 2%-3% Mo (molybdenum), so that their respective anti-corrosion ability and anti-corrosion environment are different.

L stands for low carbon. For example, 304L has lower carbon content than 304. H and S stand for high temperature resistance. For example, 310S has higher high temperature resistance than 310. 304H has higher heat resistance than 304. 316 and 316L are marine materials with strong corrosion resistance.

There are two kinds of 304 stainless steel materials: first-grade materials and second-grade materials. The second-grade materials are inferior products of steel mills. The second-grade materials are cheaper than first-grade materials. It will enter the market after a little treatment, but the quality was unstable.

2. The influence of the molding process on the performance and service life of pipe fittings

"Pipe fitting molding" is the most important step in the production process of pipe fittings. With the continuous increase of stress during the processing, the accuracy is easy to change under the action of force.

At present, most pipe fitting manufacturers mainly adopt the "cold extrusion" and "bulging" processes in the forming process. The size, wall thickness and function of the pipe fittings will be different depending on the production process. So, what kind of molding process should be used to maintain the quality stability and improve production efficiency is a very important issue. The characteristics of the two processes are:

1) "Cold extrusion" process: Put the stainless steel blank tube into the mold cavity, apply pressure to the blank through the punch fixed on the press, deforming the stainless steel blank tube to obtain the size requirements of the pipe fitting. Its main features are:

A. The surface is smooth. The general dimensional accuracy of extruded parts can reach 8-9 grades, if lubrication is used, it is second only to the polished surface. The surface of parts manufactured by extrusion method generally does not require further processing.

B. The cold extrusion process with auxiliary means can meet the product quality requirements.

C. Cold extrusion will cause the tensile stress of the pipe fittings. The cold extrusion process has the characteristics of cold deformation. During the extrusion process, the metal blank is under three-way pressure, and the metal structure is modified after deformation.

2) "Bulging" process: Use high-pressure liquid, gas or solid soft mold inside the pipeline to force the plastic change to meet the external dimensions of the workpiece. Its main feature are:

A. During bulging, the deformation of the material is limited to the fixed mold and the quality is stable. The workpiece will not wrinkle, and the surface of the formed workpiece is smooth and the springback is small.

B. During bulging, the material is under bi-directional tensile stress. Under the action of the mold, the wall thickness of the pipe is reduced and the surface area is increased to obtain the required geometry.

C. During bulging, the deformation zone of the pipe is limited to the range of the deformation zone.

The performance and service life of stainless steel pipe fittings is very important to the water supply pipelines, therefore, we should choose suitable materials and processing methods.