Welding Specification for Steel Structures of Buildings of JGJ81-2002 (Part 22)
Welding is the most widely used means of joining steel structures in buildings, so the welding specification for steel structures of buildings should be strictly followed to ensure its safety and reliability. Part 22 of the JGJ81-2002 welding specification sets forth the welding requirements for steel structures of buildings, including the welding quality requirements, welding methods, welding process parameters, preheating temperature, post-weld heat treatment and other requirements.
1. Quality Requirements
Welding quality is the basic guarantee for the reliability of steel structure of buildings. The general requirements for weld quality of steel building structures are qualified welds according to drawing dimensions and shape, without welding defects such as slag inclusion, porosity, undercut, incomplete penetration and thermal cracking.
2. Welding Method
Any welding method may be used for steel structure of buildings. It is often suitable to use manual welding, semi-automatic arc welding, tungsten inert gas shielded arc welding, submerged arc welding, etc., for the steel structure of buildings using plate components and single line welds.
3. Welding Process Parameters
The welding process parameters are required to achieve adequate weld quality and complete the welding task. The following welding process parameters must be followed in order to meet the requirements of steel structure of buildings:
(1) The welding current and voltage should be adjusted according to the welding position, thickness, diameters and welding materials.
(2) The welding speed and the wire feed speed should be selected according to the welding position, thickness, diameters, materials and welding current.
(3) The welding angle should be appropriate, the welding shall be carried out according to the longitudinal direction or on the horizontal or vertical plane, or at an angle suitable for welding.
(4) The welding gap should be adjusted according to the welding position and the gap suitable for welding.
4. Preheating Temperature
Preheating temperature is necessary for steel structures of buildings to ensure the uniform heating before welding and eliminate extra internal stresses. The preheating temperature for steel structures of buildings is 100°C for each plate component which is thicker than 20mm.
5. Postweld Heat Treatment
Post weld heat treatment can eliminate internal stresses and improve weld quality. The required postweld heat treatment process is determined by the wall thickness, welding position and welding gaps.
6. Other Requirements
(1) The qualified welding materials should meet the requirements of drawing and have the necessary mechanical properties.
(2) The welding staff must be properly trained, and the welder should have certificates issued by the construction unit.
(3) If it is necessary to increase the welding size according to the actual construction conditions, it should be approved in advance by the construction unit.
In conclusion, the welding specification for steel structures of buildings of JGJ81-2002 sets forth the welding method, process parameters, preheating temperature and other requirements for steel structures of buildings. In order to ensure its safety and reliability, operators should strictly observe the requirements and make sure that the welds are qualified without any defects.
