Incoloy800 nickel-based alloy has good thermal conductivity, high temperature corrosion resistance, stress corrosion resistance and oxidation resistance due to its high nickel and chromium content, and is commonly used in the production of electric heating pipes, heat exchangers and distillers.
Incoloy800 Chemical Composition.
cr ni c si mn
p s fe al ti
0.015 ≤0.01 Margin 020-0.40 0.20-0.50
At present, IncoloY800 nickel-based alloy is the main raw material for electric heating pipes in the market, and the main production processes of electric heating pipes include: raw steel strip inspection, argon arc welded pipe (annealing), filling magnesium powder, roll pressure reduction (annealing), bending pipe forming, diameter reduction, compression, assembly, sealing, performance testing. Material cracking is a common problem in the production process of electric heating pipes, which mostly occurs in the bending stage of pipe forming, which seriously affects the quality of electric heating pipes.
The reasons for the fracture of the elbow of the incoloy800 nickel-based alloy electric heating pipe were analyzed.
The results show that if the argon arc weld is on the outside during the bending process of the electric heating pipe, it cannot withstand the local high stress due to the weak intergranular bonding force of the columnar in the weld, which increases the risk of bending fractureIn addition, there are holes and cracks in the alloy material matrix, and stress concentration occurs in local areas, which promotes the initiation and propagation of cracks.
It is recommended to adjust the raw materials and processing technology in the following three aspects: (1) optimize the welding process parameters of argon arc welding, improve the mechanical properties of the weld, and at the same time, try to avoid the weld being on the outside during the bending process;(2) Optimize the casting and rolling process parameters to reduce defects such as shrinkage porosity, shrinkage porosity and cracks in the matrix;(3) Optimize the heat treatment process parameters and eliminate the columnar crystals in the weld.