Whether the stainless steel pipe will be bright after annealing mainly depends on the following influences and factors:
1. Whether the annealing temperature reaches the specified temperature. The heat treatment of stainless steel pipes generally adopts solution heat treatment, which is what people usually call “annealing”. The temperature range is 1040~1120℃ (Japanese standard). You can also observe through the observation hole of the annealing furnace. The stainless steel pipe in the annealing area should be in an incandescent state, but there should be no softening and sagging.
2. Annealing atmosphere. Generally, pure hydrogen is used as the annealing atmosphere. The purity of the atmosphere is preferably above 99.99%. If the other part of the atmosphere is an inert gas, the purity can be lower, but it must not contain too much oxygen or water vapor.
3. Furnace body sealing. The bright annealing furnace should be closed and isolated from the outside air; if hydrogen is used as the protective gas, only one exhaust port should be open (used to ignite the discharged hydrogen). The inspection method can be to apply soapy water on the joints of the annealing furnace to see if there is air leakage; the most likely places for air leakage are the places where the tubes enter and exit the annealing furnace. The sealing rings in this place are particularly easy to wear. Check and change frequently.
4. Protective gas pressure. To prevent micro-leakage, the protective gas in the furnace should maintain a certain positive pressure. If it is hydrogen protective gas, it generally requires more than 20kBar.
5. Water vapor in the furnace. The first is to comprehensively check whether the furnace body material is dry. When installing the furnace for the first time, the furnace body material must be dried; the second is to check whether there are too many water stains on the stainless steel pipes entering the furnace. Especially if there are holes in the pipes, do not Water leaked in, otherwise it would destroy the atmosphere of the furnace. What you need to pay attention to is these. Normally, the stainless steel pipe that should be retreated about 20 meters after opening the furnace will start to shine, so bright that it reflects. It is designed for online bright annealing of stainless steel pipe manufacturers and is based on the demand-side annealing process. According to the requirements, it consists of a complete set of equipment consisting of an IWH series all-solid-state IGBT ultra-audio induction heating power supply, gas protection device, infrared temperature measurement device, ammonia decomposition device, water circulation cooling system, cleaning device, electronic control system and voltage stabilizing device. Using an inert atmosphere as a protective atmosphere, the workpiece is heated and cooled at high temperatures without oxidation to achieve the effect of bright treatment. The equipment adopts a grouped continuous heating structure. During heating, inert gas is added to the furnace tube to reduce and protect the metal wire, making its surface very bright. (Matte matte) slows down the oxidation rate of the metal surface, further achieving anti-rust properties.