The meaning of "weld joint assembly":
1. Forced assembly in welding refers to:
When the weldments are assembled and positioned, Due to various reasons, the welded joints cannot be assembled into qualified weld seams in a free state. It must be forcibly assembled with the help of external force. Through methods such as hammering, squeezing with inclined iron, strong pull with reverse chain, hard jacking, etc., the welding joint will produce stress deformation under the action of external force to achieve the purpose of welding joint alignment. Such a pairing is a forced pairing.
2. General steel structure welding, high-strength low-alloy steel and high-alloy steel structure welding are not allowed to be forced to be combined. Except for the cold drawn welded joints, forced assembly is not allowed during pipeline installation.
The meaning of "matching device": Mechanical matching device. The matching device is a tool used to adjust the pipe-to-pipe butt joint set during pipeline installation. It is usually divided into internal and external pipe matching devices according to the location of use. There are two types of mouthpieces; according to the power source, they can be divided into hydraulic, pneumatic and mechanical forms....
Related knowledge expansion: preheating and postheating before welding are to reduce the cooling rate of the weld and prevent the joint from A hardened structure is generated and cold cracks occur. The preheating temperature before welding is generally 100-200 degrees.
Post-heating is not heat treatment and is also a slow cooling measure. The temperature of post-heating is 200-300 degrees. Some are simply for slow cooling. Some are designed for hydrogen elimination treatment. A certain post-heating temperature can make the hydrogen in the weld diffuse out and prevent it from gathering and causing cracks. The post-heat holding time should be determined according to the thickness of the workpiece, and generally it will not be less than 0.5 hours.
There are many post-weld heat treatments, which are mainly divided into four types:
1 Post-weld heat treatment performed below the lower transition temperature, such as stress relief annealing, the temperature is generally 600- Between 700 and 700, the main purpose is to eliminate welding residual stress.
2 Post-weld heat treatment above the upper transition temperature, such as normalizing, with a temperature between 950-1150, refines the grains and improves the material. Mechanical properties, such as solid solution and stabilization treatment of stainless steel, the temperature is around 1050, which improves the corrosion resistance of stainless steel. Especially the ability to resist intergranular corrosion. Another example is quenching. Different quenching processes can achieve different effects, improving the wear resistance and hardness of steel.
3. First perform the treatment above the upper transition temperature and then perform the heat treatment below the lower transition temperature. For example, normalizing plus tempering, quenching plus tempering, etc.
4 Post-weld heat treatment between upper and lower transition temperatures. Between 750-900, some materials are effectively strengthened by recrystallization annealing, etc.