Influencing factors of seamless elbow quality
Posted by zora li on August 30th, 2023
Influencing factors of seamless elbow quality
The temperature in the furnace during production did not reach the specified temperature
The raw material for making seamless elbows - round tube billet, the billet is sent into the furnace for heating at a temperature of about 1200 degrees Celsius; flanged pipe fittings are usually solid solution treated in the temperature range of 1040 to 1120 ° C (Japanese standard) to process. It can be observed through the observation hole of the annealing furnace, and the flange fittings in the annealing area should be in an incandescent state, but not softened and sagging.
Improper fuel selection
When the billet is put into the furnace for heating, fuel needs to be put in. The fuel is hydrogen or acetylene, especially hydrogen, and usually pure hydrogen is used as the annealing atmosphere, and the purity of the atmosphere is preferably above 99.99%. If another part of the atmosphere is an inert gas, the purity may be reduced, making the seamless elbow much more brittle, and damage and leakage problems will occur when encountering conditions such as high pressure and high temperature. It is important to note that the inert gas must not contain too much oxygen or water vapor.
The protection pressure in the furnace is wrong
In order to prevent micro-leakage of seamless elbows, the protective gas in the furnace should maintain a certain positive pressure. If it is hydrogen protective gas, it usually needs to exceed 20kBar.
Furnace is not sealed well enough
The bright annealing furnace should be closed and isolated from the outside air. If hydrogen is used as shielding gas, open only one vent (for igniting the exhausted hydrogen). You can use soapy water to apply the inspection method to the crevices of the annealer joints to see if the gas is flowing, because the places where the gas is easily transported are where the annealer enters the pipe and where it exits the pipe. The seals here are particularly prone to wear, so check and replace them frequently.
