1. What is the minimum wall thickness of 10# seamless steel pipe for general structural use?
Answer: According to GB/T 8163 standard, the minimum wall thickness of 10# seamless steel pipe for general structural and fluid transportation use is 1.5mm (for pipes with outer diameter ≤14mm). For pipes with larger outer diameter, the minimum wall thickness increases accordingly (e.g., outer diameter 57mm, minimum wall thickness 3.5mm), which is determined by the bearing capacity and processing technology.
2. Can 35# seamless steel pipe be welded? What should be paid attention to during welding?
Answer: Yes, 35# seamless steel pipe can be welded, but because it is medium carbon steel, the welding performance is worse than low-carbon steel (10#, 20#). During welding, it is necessary to pay attention to: preheating the welding area to 150-250℃ before welding to prevent cold cracks; using low-hydrogen welding electrodes (such as E5015) to reduce hydrogen content in the weld; performing post-welding heat treatment (tempering at 550-600℃) to eliminate welding stress and improve the toughness of the weld.
3. What is the tensile strength range of 20# seamless steel pipe?
Answer: According to the national standard, the tensile strength of 20# seamless steel pipe is 410-550MPa, the yield strength is ≥245MPa, and the elongation is ≥25%. The specific value will vary slightly according to the production process (hot rolling, cold drawing) and heat treatment state, but it must meet the requirements of GB/T 8163 standard.
4. What is the reason for the corrosion of seamless steel pipes in the chemical industry? How to prevent it?
Answer: The main reasons for corrosion are: chemical corrosion by acidic, alkaline or salt-containing media in the chemical industry; electrochemical corrosion caused by the formation of micro-batteries on the surface of steel pipes. Prevention methods: choose corrosion-resistant steel grades (such as 316L stainless steel seamless pipes) for strong corrosive media; coat the inner and outer surfaces of steel pipes with anti-corrosion coatings (such as epoxy resin, polyethylene); use corrosion inhibitors in the transported medium to reduce corrosion.
5. What is the difference between hot-rolled and cold-drawn 10# seamless steel pipe?
Answer: Hot-rolled 10# seamless steel pipe: produced by hot rolling process, with large outer diameter and wall thickness, rough surface, low dimensional accuracy, but high production efficiency and low cost, suitable for general structural and low-pressure fluid transportation. Cold-drawn 10# seamless steel pipe: produced by cold drawing process on the basis of hot-rolled pipe, with small outer diameter and wall thickness, smooth surface, high dimensional accuracy, good mechanical properties, but high cost, suitable for precision mechanical parts and high-precision fluid transportation pipelines.
