Welding Process Parameters for Butt Joint of Low Alloy Pearlitic Heat Resistant Steel Pipe
1. Introduction
Low alloy pearlitic heat resistant steel is a special kind of steel with higher temperature strength and resistance to oxidation and corrosion. It has good mechanical properties, low carbon content and high hardenability, so it is often used as a heat resistant steel. It has wide application in industries such as power generation and process industries, where components working at high temperatures often need to be joined together. Butt joint welding is the most popular welding method used for joining low alloy pearlitic heat resistant steel, due to its advantages, such as good weldability, strong joint and surface finish.
2. Welding Process Parameters
Welding of low alloy pearlitic heat resistant steel pipe butt joints require certain welding process parameters in order to ensure high-quality welding results. The main welding process parameters for welding of low alloy pearlitic heat resistant steel pipe butt joints include electrode type and size, welding heat input, welding current and voltage, welding angle, preheat temperature and consumable materials.
2.1 Electrode Type and Size. The type and size of electrode is critical for butt joint welding of low alloy pearlitic heat resistant steel pipe. Covered electrodes are commonly recommended for low alloy pearlitic heat resistant steel pipe butt joint welding, such as AWS E80T-), E8018-C3 and E9018s-M.These electrodesare suitable for welding of low alloy pearlitic heat resistant steel and provide good tensile strength and toughness. The electrode diameter should be selected based on the thickness of the steel. A larger electrode is usually recommended for thicker steel, and a smaller electrode should be used for thinner steel.
2.2 Welding Heat Input. The welding heat input should be controlled to ensure proper weld fusion and bead profile. For butt joints of low alloy pearlitic heat resistant steel pipe, it is recommended to use low welding heat input of less than 650J/mm to prevent heat affected zone (HAZ) cracks. Higher welding heat inputs can lead to reduction in strength and toughness of the weldment.
2.3 Welding Current and Voltage. The welding current and voltage should be set according to the thickness and type of steel. A higher welding current and voltage should be used for thicker steel, while a lower current and voltage should be used for thinner steel. The welding current and voltage should be adjusted in order to achieve a smooth, continuous and uniform bead profile.
2.4 Welding Angle. The welding angle plays an important role in achieving good weld quality. The welding angle should be set between 65° and 85° for proper fusion,impact and surface finish. A smaller welding angle should be used if weld overcrowning is expected.
2.5 Preheat Temperature. The preheat temperature should be determined based on the size of the steel. The recommended preheat temperature for low alloy pearlitic heat resistant steel pipe is 400 to 600°C (750 to 1150°F). Preheating can reduce stress and improve weldability of the steel.
2.6 Consumable Materials. Consumable materials for low alloy pearlitic heat resistant steel pipe butt joint welding include flux and shielding gas. The flux should be compatible with the steel and electrode type being used for welding. Shielding gases such as helium, argon, and carbon dioxide are commonly used for butt joint welding of low alloy pearlitic heat resistant steel pipe.
3. Conclusion
The welding process parameters for butt joint welding of low alloy pearlitic heat resistant steel pipe include electrode type and size, welding heat input, welding current and voltage, welding angle, preheat temperature, and consumable materials. Welding process parameters should be carefully selected in order to achieve good weld quality.
