Carbon steel elbow

Carbon steel elbow can be divided into long radius elbow and short radius elbow according to its curvature radius. A long radius elbow is the outer diameter of a pipe whose curvature radius is equal to 1.5 times, that is, R = 1.5D. Short radius elbow means that its curvature radius is equal to the outside diameter of the pipe, that is, R = 1.0D. (D is the diameter of elbow, R is the radius of curvature. D can also be expressed in multiples. There are about seventeen kinds of pipe standards, which are the same as those in the United States. They are: Sch5s, Sch10s, Sch10, Sch20, Sch30, Sch40s, STD, Sch40, Sch60, Sch80s, XS; Sch80, Sch100, Sch120, Sch140, Sch160, XXS, among which STD and XS are the most commonly used. According to the angle of elbow, there are 45 degree elbow, 90 degree elbow and 180 degree elbow. The implementation standards include GB/T 12459-2005, GB/T 13401-2005, GB/T 10752-1995, HG/T 21635-1987, D-GD0219, etc.

Stainless steel elbow

1. When using the electrode, it should be kept dry. The Ti-Ca type should be dried at 150 C for 1 hour. The low hydrogen type should be dried at 200-250 C for 1 hour (it can not be repeatedly dried, otherwise the coating is easy to crack and peel), so as to prevent sticking oil and other dirt on the electrode coating, so as to avoid increasing the carbon content of the weld and affecting the quality of the weld. Carbides are precipitated by repeated heating during elbow welding, which reduces corrosion resistance and mechanical properties. It is easy to crack because of its high hardness after welding. If the same type of electrode is used for welding, it must be preheated above 300 ~C and slowly cooled around 700 ~C after welding. If the weldment can not be heat treated after welding, chromium-nickel stainless steel electrode should be selected.

2. In order to improve the corrosion resistance and weldability of stainless steel elbows, appropriate addition of stability elements Ti, Nb, Mo, etc. can make the weldability better. When using the same type of chromium stainless steel welding rod, preheating above 200 C and tempering around 800 C after welding should be carried out. If the weldment can not be heat treated, chromium-nickel stainless steel electrode should be selected.

Alloy elbow

Alloy elbow is a general term for various elbows. Its function is to connect two pipes with the same nominal diameter to make the pipe turn at 90 degrees or other angles. Its material is various, and alloy elbows are widely used.

Manganese steel alloy elbow is usually used in concrete pipeline and slurry pipeline because of its excellent performance of bearing impact, extrusion and material wear. High manganese steel alloy elbows are used in pipelines with intense fluid flow and strong impact; nickel steel alloy elbows are usually used in normal temperature pipelines with high concentration of oxidizing acid (nitric acid, sulfuric acid), etc., but they will be seriously corroded in the pipelines of reducing acid (hydrochloric acid, dilute sulfuric acid, etc.), unless they are used in pipelines with high concentration of oxidizing acid (nitric acid, sulfuric acid, etc.). The concentration of hydrochloric acid is very low; the elbow of martensite alloy has higher high temperature strength, oxidation resistance and water vapor corrosion resistance under 650℃, but its weldability is poor. Therefore, it is often used in high temperature steam pipeline and water gas pipeline.

Implementation standards: GB/T 12459-2005, GB/T 13401, GB/T 10752-1999.