Thick-walled steel pipes are widely used steel varieties. It directly affects the economic benefits and the lives of personnel. Every country in the world attaches great importance to the inspection of thick-walled steel pipes, and various non-destructive testing (NDT) methods are used to carry out strict inspections on thick-walled steel pipes. To a certain extent, the corresponding maintenance and maintenance should be paid attention to during the use of thick-walled steel pipes. In a general sense, the special person should be set up to conduct daily patrol inspections of thick-walled steel pipes to check whether the uprights and backing plates are sinking or loosening, whether all fasteners of the frame body are slippery or loose, and whether all the components of the frame body are complete and complete; The thick-walled steel pipe foundation should be well drained. After the rain, the base of the thick-walled steel pipe frame should be inspected comprehensively. It is strictly forbidden to sink the accumulated water of the thick-walled steel pipe base; The wind rope, etc. are fixed on the thick-walled steel pipe, and it is strictly forbidden to hang heavy objects on the thick-walled steel pipe; it is strictly forbidden for anyone to arbitrarily remove any parts on the thick-walled steel pipe; in case of strong winds, heavy fog, heavy rain and heavy snow weather of grade 6 or above, the thick-walled steel pipe should be suspended. For steel pipework, the work can be continued after checking that there is no problem before resuming work.
Thick-walled steel pipe performance and economy:
In addition to the above-mentioned structural types of pipe fittings used in actual piping engineering, there are other types of pipe fittings to meet the requirements of various working conditions, especially special working conditions. In engineering design or selection, the higher the strength level of the pipe fittings, the higher the performance, but the greater the cost of the project, which will cause waste. From the perspective of economic benefits, while meeting the requirements of engineering design and reducing costs as much as possible, it is often easy to form the result that the selected pipe fittings generally have a small number of varieties, which is not conducive to the management, regulation and design changes of on-site construction materials. Substitute materials, etc. Therefore, the selection of pipe fittings should be comprehensive and economical, and it is advisable to reduce the variety of pipe fittings as much as possible. In addition, factors such as on-site construction conditions, construction level, and procurement cycle of pipe fittings should also be paid attention to in the selection of pipe fittings. Under specific circumstances, the possibility of using reinforced pipe joints, mitered elbows, and on-site bending of small-diameter pipes should also be considered. At the same time, we also have a good understanding of the production capacity and products of the pipe fittings factory, as well as the market supply situation.
Causes and adjustment of the uneven wall thickness of steel pipes:
1. The reasons the uneven wall thickness of the spiral shape are: the uneven wall thickness caused by the adjustment reasons such as the uneven rolling center line of the piercer, the inclination angle of the two rolls, or the reduction amount in front of the plug is too small, generally along the whole length of the steel pipe. Spiral distribution. During the rolling process, the uneven wall thickness caused by the premature opening of the centering roll, improper adjustment of the centering roll, and jitter of the ejector rod are generally distributed in a spiral shape along the entire length of the steel pipe.
Measures: Adjust the rolling center line of the piercing machine to make the inclination angles of the two rolls equal, and adjust the rolling mill according to the parameters given in the rolling table. For this situation, adjust the opening time of the centering roller according to the speed of the capillary outlet, and do not open the centering roller too early during the rolling process to prevent the ejector from shaking and causing uneven wall thickness. The opening of the centering roller needs to be adjusted appropriately according to the change in the diameter of the capillary, and the amount of the capillary runout should be considered.
2. Causes of uneven linear wall thickness: The height adjustment of the saddle for pre-piercing of the mandrel is not appropriate, and the mandrel is pre-pierced when it touches the capillary on a certain side, which causes the temperature of the capillary to drop too fast on the contact surface, resulting in uneven wall thickness or even Pulling concave defects. The roll gap of continuous rolling is too small or too large. The centerline deviation of the tube mill. Uneven reduction of single and double racks will cause linear symmetrical deviations in the direction of the single rack (over-thick) and the over-thickness of the double rack. The mortar is broken, and the difference between the inner and outer roll gaps is large, which will cause the straight line asymmetric deviation of the steel pipe. Improper adjustment of continuous rolling will cause uneven wall thickness in straight lines.
Measures: Adjust the height of the mandrel pre-piercing saddle, and ensure that the mandrel and the capillary are centered. The roll gap should be measured when changing the pass type and rolling specifications so that the actual roll gap is consistent with the rolling table. Adjust the rolling centerline with the optical centering device, and correct the centerline of the tube mill during the annual overhaul. Replace the broken frame in time, measure the inner and outer roll gaps of continuous rolls, and replace them in time if there is a problem. During continuous rolling, steel drawing and stacking should be avoided.
3. Causes of the uneven wall thickness of the head and tail: The front end of the tube blank is cut inclination, the bending is too large, and the centering hole of the tube blank is not correct, which is easy to cause the uneven wall thickness of the steel tube head. When piercing, the elongation coefficient is too large, the roll speed is too high, and the rolling is unstable. The unstable steel throwing of the piercer can easily cause uneven wall thickness at the end of the capillary tube.
Measures: Check the tube blank to prevent the front end of the tube blank from being cut in inclination the amount of reduction is large, and the centering hole should be corrected for hole type change or maintenance. A lower piercing speed is used to ensure rolling stability and uniformity of capillary wall thickness. When the roll speed is adjusted, the matching guide plate is also adjusted accordingly. Pay attention to the use status of the guide plate and increase the inspection of the guide plate bolts, reduce the movement of the guide plate during rolling, and ensure the stability of the steel casting.
Post time: Nov-23-2022