Inspection issues for the preheating furnace coil
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Excuse me, does anyone who is an expert know what material the preheating furnace coil is made of? What type of welding rod should be used? What method is used to bend pipes?
The furnace tubes of our heating furnace are made of 304H; due to frequent start-up and shutdowns, the tubes experience rapid temperature changes, which shortens their lifespan. It is recommended to contact the manufacturer for repairs. After all, they are more professional.
The TS-308H material can be used. Bending pipes can be done using a pipe bender. Make sure the weld joint has a proper bevel.
The material used for the furnace tubes in the radiation section of our preheating furnace is HK40, while the material for the furnace tubes in the convection section is TP304H. The material used for elbows is the same as that for the furnace tubes. The specific welding materials can be selected in accordance with the three standards GB/T5117-1995, GB/T5118-1995, and GB/T983-1995. Welded joints are formed from chromium-molybdenum steel and austenitic steel; when the operating temperature is ≤425°C, austenitic welding materials with 25% Cr–13% Ni or higher can be used； When the operating temperature is ≥425°C, nickel-based welding materials (Nickel 307) should be used. In my personal opinion, specific details can be discussed based on one’s actual manufacturing conditions and the manufacturer involved.
We use HK40 for the radiation section of our preheating furnace, and A432 for welding. The convection section is 304, and A102 or E308 is used for welding. The heating furnace coil is made of 304. It seems that there’s no need to use elbows; instead, the fittings can be welded directly.