At present, the application of stainless steel pipes in the market is very extensive, and it plays a very important role in many industries. In order to reduce hardness, improve plasticity, refine grain, and eliminate internal stress, annealing is necessary.
However, many users report that the yellow or blue stainless steel tube after annealing always fails to achieve the expected bright effect, so how to solve this problem? Now, Hangao (SEKO) will bring you an overview.
Whether the stainless steel tube is bright after annealing mainly has the following factors:
1. If the surface turns yellow, it may be caused by unstable heating temperature, which means that the surface temperature is high and the inside temperature is low. At this time, we need to check whether the annealing temperature reaches the specified temperature. The reason is that there is a problem in the control of the annealing temperature, or in the design of the division of the temperature zone of the annealing furnace.
The heat treatment of stainless steel is generally solution heat treatment, commonly known as "annealing". The temperature range is 1040 ~ 1120 (Japanese standard). It can also be observed through the observation hole of the annealing furnace. The stainless steel pipe in the annealing area should be incandescent, but not softened and sagging.
At present, the steel pipe annealing furnaces on the market are mixed with good and bad, and the prices vary greatly. It is difficult for users who do not understand the process technology and working principle to distinguish between good and bad.
2. The reason can also be found from the process flow and technology, which is related to the temperature setting, the surface cleanliness of the stainless steel tube, and the material of the stainless steel tube.
3. Annealing atmosphere. The annealing atmosphere generally uses pure hydrogen, and the purity of the atmosphere must reach 99.99%. If the other part is an inert gas, the purity can be lower. However, the protective gas must not be doped with too much oxygen and water vapor.
It is worth noting that if the stainless steel pipe itself that enters the furnace body has too much oil or water stains, the protective atmosphere in the furnace will be destroyed, and the purity of the protective gas will not be achieved, which will also affect the brightness. Therefore, we usually suggest that customers can add a cleaning and drying device before the bright annealing equipment. It can use high-speed hot water flow to take away the surface oil stains, and then quickly dry the water stains on the surface of the steel pipe through a high-speed air knife, and then anneal, the resulting bright effect will be greatly improved.
4. The sealing performance of the furnace body. The bright annealing furnace should be closed and isolated from the outside air; when hydrogen is used as a protective gas, only one exhaust port is open (for igniting the exhausted hydrogen). The inspection method can be to smear the joints of the annealing furnace with soapy water to see if there is any air leakage; the place where the gas is most likely to escape is the place where the annealing furnace enters and exits the pipe. The sealing ring in this place is particularly prone to wear and tear, so it should be checked and replaced frequently.
5. There is steam in the stove. On the one hand, check whether the furnace body material is dry, and the furnace body material must be dried for the first time; secondly, whether there is too much water stain left on the stainless steel pipe entering the furnace. Especially if there are holes on the surface of the pipe, don't let it leak into the pipe, otherwise it will completely destroy the atmosphere in the furnace.
Sincerely hope that all respected customers will pay attention to the above points when using induction heating bright annealing funace. If the annealed stainless steel pipe does not achieve the expected effect, just feel free to contact our company's technician department or after-sales team.
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Iris Liang
Senior Sales
E-mail: sales3@hangaotech.com
Mobile phone: +86 13420628677
QQ: 845643527
Wechat/ Whatsapp: 13420628677
