Unlike seamless casing, the brightness of the seamless steel pipe after annealing determines the quality of the product. There are also many influencing factors, among which the five most important factors are as follows:
1. Whether the annealing temperature reaches the specified temperature. Stainless steel heat treatment is generally taken by solution heat treatment, which is commonly known as “anneal”, the temperature range of 1040 ~ 1120 °C (Japanese standard). You can also observe through the observation hole in the annealing furnace. The stainless steel seamless tube in the annealing zone should be incandescent, but no soft sagging occurs.
2. Annealing atmosphere. In general, pure hydrogen is used as the annealing atmosphere, and the purity of the atmosphere is preferably 99.99% or more. If the other part of the atmosphere is an inert gas, the purity can be low, but it must not contain too much oxygen and water vapor.
3. Furnace tightness. The bright annealing furnace should be closed and isolated from the outside air; only one exhaust port is used for the protection of hydrogen gas (used to ignite the discharged hydrogen gas). The inspection method can be used soapy water wiped in the joints of the annealing furnace joints to see whether the run-off; where the easiest place to run gas is the place where the annealing furnace enters the pipe and the place where the pipe is out, where the sealing ring is particularly easy to wear, Always check for frequent changes.
4. Protective gas pressure. In order to prevent the occurrence of micro-leakage, the protective gas in the furnace should maintain a certain positive pressure. If it is a hydrogen gas, it generally requires more than 20kBar.
5. Water vapor in the furnace. On the one hand, check the furnace material is dry, the first time the furnace, the furnace material must be dried; the second is the stainless steel seamless tube into the furnace if there is excessive water stains, especially if there is a hole in the pipe, do not leak water, go in Otherwise, the furnace atmosphere will be completely destroyed.
It is basically these things that should be noticed. Normally, after the furnace is opened, the stainless steel seamless pipe that should be retreated about 20 meters will start to shine, and the kind of light that looks bright.