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Factors Affecting The Performance And Life Of Stainless Steel Pipe Fittings

Jan. 07, 2020

China stainless steel pipe fittings chinahas a long service life. From the perspective of the use of stainless steel pipes abroad, the service life of stainless steel water pipes can reach 100 years, at least 70 years, the same life as buildings. The most prominent advantage of stainless steel pipe fittings is their corrosion resistance. If stainless steel pipes are used and maintained correctly during use, they can effectively extend their service life.

(I) Influence of material on service life of pipe fittings

The main difference between 304 and 304L is stainless steel: 304 contains C (carbon) ≤ 0.08%, while 304L contains C ≤ 0.03%; 316 is 1% higher than 304 with NI (nickel) than 304—2 %, Mainly reducing the Cr (chromium) content and increasing the Mo (molybdenum) by 2% to 3%, so the respective corrosion resistance and corrosion resistance environment are different.

L stands for low carbon, such as 304L has lower carbon content than 304, H and S stand for high temperature resistance. For example, 310S is more resistant to high temperature than 304H, 304H is more heat resistant than 304, 316 and 316L are marine materials and have strong corrosion resistance.

There are two types of 304 stainless steel: first grade and second grade. The secondary material is also the inferior product of the steel mill. The main differences are: the surface of the secondary material, the nickel content, the uneven thickness, etc., which are cheaper than the primary material. The steel mill entered the market after a little processing, but the quality was unstable.

Stainless Steel Castings

Stainless Steel Castings

(B) the impact of stainless steel castings on the performance and life of the fittings

"Pipe fitting forming" is the most important step in the production process of pipe fittings. With the continuous increase of stress during the processing of the pipe, the accuracy is easily changed under the action of force.

At present, most pipe fitting manufacturers mainly adopt the "cold extrusion" and "bulging" processes in the forming process. Depending on the production process, the size, wall thickness, and function of the pipe will vary. Therefore, what molding process is used to maintain stable quality and improve production efficiency is a very important issue. The characteristics of the two processes are described below.

(1) The surface is smooth and clean. Extrusion parts generally have a dimensional accuracy of 8 to 9, which is second only to polished surfaces if lubrication is used. Surfaces of parts manufactured by extrusion methods generally do not require further processing.

(2) Auxiliary means of cold extrusion process configuration can meet product quality requirements. For example, the "U-shaped groove" and "three-way pull-outs" of the pipe are formed. During the extrusion process, the feeding method is used to achieve the wall thickness of the "U-shaped grooves" and "three-way pull-outs", ensuring product quality.

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

2. "Bulging" process: The bulging process is to pass a high-pressure liquid, gas or solid soft mold inside the tube blank to force the tube to plastically change to meet the external dimensions of the workpiece. main feature:

(1) During bulging, the deformation of the material is limited to the fixed mold, and the quality is stable. The workpiece does not wrinkle, and the surface of the formed workpiece is smooth with little rebound.

(2) During bulging, the material is in a state of stress in both directions. 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.

(3) During bulging, the deformation area of the pipe is limited to the scope of the deformation zone, and the pipe is not transferred outside the deformation zone. For example, the formation of the U-shaped groove of the pipe is achieved by the local thinning of the pipe.

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