This article introduces the common problems that occur when the steel plate rolling machine rolls steel pipe tiles or pipe joints, how to avoid these problems, and what factors to consider when selecting the specifications of the plate rolling machine. The ability to calculate the maximum indenter thickness and maximum roll arc through the selected plate rolling machine for peer reference.
For the processing and forming of pressure steel pipes, in water conservancy and hydropower projects, it is rare to use a press to press tiles (or pipe joints), and usually use a steel plate rolling machine to roll them. The type of plate rolling machine usually uses a 4-roll plate rolling machine, a 3-roll horizontal downward adjustment type plate rolling machine, a 3-roll horizontal and vertical upward adjustment type (commonly known as universal type) plate rolling machine, etc. to roll steel pipes. Read More: Bending Machine Wikipedia
5 common problems in making pressure pipes by steel plate rolling machine
- Common problem 1: Roll tiles (pipe joints) after splicing metal sheets. Or after the longitudinal weld seam is welded after rolling, use the steel plate rolling machine to perform rolling correction and arc repair.
- Common problem 2: Since the rated capacity of the rolling capacity of the steel plate rolling machine does not reach the force required for the pre-bending of the sheet thickness, the end of the plate has an over-standard straight edge. Therefore, in order to prevent the appearance of the over-standard straight edge, the sheet is passively lengthened Length, that is to say, extend and reserve a length of 50mm or more at both ends of the sheet. After the tile is rolled and formed, cut off the excess length at both ends.
- Common problem 3: Due to insufficient rated capacity or improper operation of the steel plate rolling machine, tiles or pipe joints have excessive straight edges in the longitudinal weld.
- Common problem 4: When the plate is pre-bending, due to the high pressure of the upper roller, pre-bending is often the main index to determine the rated capacity of the steel plate rolling machine. When the lower pressure of the upper roller exceeds the rated capacity of the plate bending machine, coupled with the failure of the hydraulic system and improper operation, it will cause the universal joint of the reducer to crack and fall off, and even cause damage to the steel plate rolling machine equipment such as broken rolls.
- Common problem 5: The diameter-thickness ratio of the steel pipe exceeds the requirements of cold rolling, and the plasticity and toughness of the tile or pipe joint are reduced by direct installation without annealing after rolling.
Solution of 5 common problems
Solution for Common problem 1
Compared with the base metal, welded joints often have poor uniformity of grain size, high residual stress and stress concentration, high and uneven strength and hardness, poor plasticity and toughness, reinforcement or unevenness at the thickness of the weld, undercut of the weld toe, etc.
When the coiled plate is rounded after tailor welding or the longitudinal weld is rectified and arc repaired by the plate rolling machine after welding, due to the effect of cold work hardening, the mechanical properties of the welded joint and its vicinity will tend to deteriorate, resulting in new defects and even cracks. So as to bury the quality hidden trouble for the power station operation in the future. Therefore, it is not allowed to make steel pipe tiles or pipe joints according to this reverse process.
Solution for Common problem 2 and Common problem 3
The main reason is that the rated capacity of the plate rolling machine cannot meet the steel pipe material, yield ratio, plate thickness, curvature, plate width, and taper required for forming force requirements. In order to prevent the straight edge from exceeding the standard, it is forced to extend the reserved amount of the length of the sheet metal to meet the requirements of the radian of the sheet end of the steel pipe and the straight edge of the sheet end, which will lead to waste of the sheet metal. , the wasted sheet will become larger and larger.
Solution for Common problem 4
The main reason is that the hydraulic control system runs with a disease, the steel plate yield ratio is too high, the thickness is too thick, the curvature is too large, the plate width is large, etc. The second is the operation error, which continues to apply downward pressure through the upper roller to pre-bend the plate.
Solution for Common problem 5
To avoid this situation, when designing steel pipes, especially high-head, small-diameter thick-walled steel pipes, not only the water energy storage capacity must be considered, but also the material required for the steel pipe, yield ratio, plate width, plate thickness, The influence of processing techniques such as curvature and taper on the mechanical properties of steel pipes. If the design does not meet the requirements for the diameter-thickness ratio of steel pipes and cold rolling requirements, then when processing steel pipe tiles or pipe joints, annealing heat treatment should be carried out after hot rolling or cold rolling of the sheet metal. In this way, the ductility and toughness of the steel pipe caused by cold rolling can be recovered and the brittleness can be reduced.
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