After annealing the stainless steel pipe, the brightness of the pipe determines the quality of the product. There are many influencing factors. This paper gives the following 5 relatively important factors.
The first is whether the annealing temperature is up to the specified temperature. The heat treatment of stainless steel pipes is usually treated by solid solution heat treatment, also known as annealing treatment. The temperature range of the process is 1040-1120 degrees. In the process of actual processing, it can also be observed through the observation hole of the annealing furnace. The most appropriate is that the stainless steel pipe in the annealed zone is just dealing with the incandescent state and does not appear the softening droop.
The second is the atmosphere of annealing. The pure hydrogen is usually used as an annealing atmosphere. The purity of the atmosphere is better than 99.99%. If the other part of the atmosphere is inert gas, the purity of the atmosphere can be lowered a little, but it is absolutely impossible to contain too much oxygen and water vapor.
The third is the sealing property of the furnace body. A bright annealing furnace is closed, isolated from the outside air, and uses hydrogen as a protective gas. Only one exhaust port is used (used to ignite the discharged hydrogen). The inspection method can be used in soapy water on the gap between the various joints of the annealing furnace to see whether there is a running gas phenomenon. The most easy place to run gas is the place where the annealing furnace enters the pipe and the place where the pipe is out. The sealing ring of this place is very easy to wear and often check the regular change.
The fourth is to protect the gas pressure. To avoid the occurrence of micro leakage, the protective gas in the furnace must be kept at a positive pressure. If it is a hydrogen protection gas, it usually requires more than 20kBar.
The fifth is the water vapor in the furnace. On the one hand, check whether the furnace material is dry or not, for the first time to install the furnace, the material of the furnace must be dried; the other is to see whether there is too much water stains in the stainless steel pipe in the inlet, especially if there is a hole on the stainless steel pipe, so do not leak in, otherwise it will break the atmosphere in the furnace.
The last thing to understand is that if everything is normal, the stainless steel pipe will start to shine or even reflect light after annealing about 20 meters.
Source: China Stainless Steel Pipes Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)