The form of large-diameter steel pipe cooling: Large-diameter steel pipes are steel pipes with an outer diameter of 1000MM or more. Large-diameter seamless steel pipes are made of steel ingots or solid tube blanks perforated into gross pipes, then hot-rolled, cold-rolled, or cold-drawn.


1. Chain cooling bed. Historically, chain cooling beds with simple structures and low costs were mostly used. However, because it is easy to cause chain dislocation and bend large-diameter steel pipes, and large-diameter steel pipes cannot be freely collected from the input roller table to the cooling bed entrance, it is rarely used now.
2. Step-by-step cooling bed. This cooling bed is composed of walking beams and fixed beams. The cooled large-diameter steel pipe is held up by the stepping beam, moves forward a certain distance, and then placed in the groove of the fixed beam. Properly adjusting the stroke of the rack can make the large-diameter steel pipe roll twice with each step, thereby straightening the large-diameter steel pipe. Currently, most of the newly built pipe rolling units use stepping rack cooling beds.
3. Spiral cooling bed. This kind of cooling bed relies on the spiral line on the screw rod to push the large-diameter steel pipe on the cooling bed forward for cooling. As the spiral rod rotates, in addition to the forward thrust, the large-diameter steel pipe also receives a lateral thrust. Therefore, it moves sideways while moving forward but only moves forward. When the cooling rate is faster, the carbon content and alloy composition are higher, the uneven plastic deformation generated under the action of thermal stress during the cooling process is larger, and the residual stress formed is larger. On the other hand, due to the change of the structure of steel during the heat treatment process, that is, when austenite transforms into martensite, the increase in specific volume will be accompanied by the expansion of the volume of the workpiece, and various parts of the workpiece will undergo phase transformation, resulting in inconsistent volume growth and the formation of structures. stress. The final result of tissue stress changes is that the surface layer is subject to tensile stress and the core is subject to compressive stress, which is the opposite of thermal stress.


Construction preparation before large-diameter steel pipe welding:
1. Organize relevant operators, familiarize themselves with construction drawings and procedures, formulate welding procedures, and compile welding operation instructions.
2. Welders should be trained in corresponding projects and have operating qualification certificates for corresponding projects.
3. Check whether the roundness and misalignment of the arriving steel pipes meet the relevant technical requirements.
4. Check the surface of metal pipe sections for defects such as scars, cracks, severe corrosion, etc.
5. Before installing large-diameter steel pipes, the pipe sections should be measured and numbered one by one. It is advisable to use pipe sections with small diameter differences for butt welding.
6. When welding in windy, rainy, or snowy weather, there is a windproof, rainproof, and snowproof shed.
7. Before welding, the welder should clarify the requirements and welding measures.