Prevention and treatment of wave deformation of bo

2022-07-31
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Prevention and treatment of wave deformation on the web of crane jib

I. causes of wave deformation on the web of crane jib

1. The steel plate itself is distorted and deformed due to transportation and storage. The internal stress is not completely eliminated before processing and welding. After welding into the web, the internal stress is superimposed, resulting in wave deformation

2. During the blanking process, the local internal stress of the web material causes local wave deformation

3. During the welding of the box, the size of the web plate cannot be corrected due to the welder's equipment and the size error of the brace in the box, which can not guarantee the correct geometric shape of the web plate after welding, making the web plate locally concave and convex

4. Due to the influence of overload and cable-stayed high temperature but high cost in use, the boom deflects seriously and the web plate generates wave deformation

II. Countermeasures to prevent wave deformation of web plate

1. First straighten and flatten the steel plate on the plate machine, and then use the shot blasting machine to eliminate the internal stress of the steel plate and remove the oxide skin after blanking. In particular, the small-size steel plate used for welding the web plate shall be leveled and pretreated with a plate machine before and after welding; If there is no plate machine, the welded long steel plate can be placed on the platform and hammered around the weld with a wooden hammer to eliminate the internal stress

2. Use the numerical control cutting machine to cut both sides of the web at the same time, so as to avoid the disadvantages such as dimensional error and difficult to eliminate the internal stress during unilateral cutting, and greatly reduce the generation of wave deformation

3. When welding the boom box, the steel wire shall be pulled between the marks at both ends as the benchmark of the web internal support tooling to ensure that the inner side of the web is in the same straight line

4. In the process of use, it is absolutely forbidden to overload lifting and diagonal pulling, and it is not allowed to lift and pull buried or frozen objects. Avoid sudden lifting and stopping of the boom during operation. The upper camber or lower deflection value of the boom shall be frequently detected to prevent wave deformation of the web caused by the lower deflection of the boom

when the web plate has wave deformation, it shall be corrected according to JB technical conditions for general bridge cranes. In the area within h/3 of the cover plate (H is the height of the web plate), when the thickness of the web plate is greater than or equal to 6mm, the waviness shall not exceed 0.7 times the thickness of the web plate, and the waviness in other areas shall not exceed 1.2 times the thickness of the web plate

at present, the flame correction method is often used to correct the wave deformation of the web. In the specific correction process, it is better to correct from the convex part. The spiral heating method can be used. The diameter of the spiral track is mm and the temperature is between ℃. If the spiral does not eat spicy food, the circle is too large. When the outer ring is heated, the inner ring has cooled down; If the helix is too small, the helix cannot be separated and the contraction effect is poor

the heating temperature can be measured with a point thermometer or judged according to the color of the steel plate. The steel plate at ℃ is cherry red. When the heating circle reaches this temperature, hammer the outer ring symmetrically and then hammer the center of the circle until the protruding part is connected or the board needs high technology to be repaired and leveled The hammering shall be stopped when the invariance of the up and down movement position of the temperature energy resistant table surface drops to ℃, otherwise the steel plate is easy to crack because it enters the blue brittle state The residual marks can be left to shrink during further cooling to remove compensation

a steel plate with a round hole in the middle can be used to weld and pull out the concave part for correction of the concave part, and the external force can be applied by the on-site lifting equipment or other guiding devices. Flame heating can be used during drawing, which is convenient and can prevent springback after cold drawing. After the concave part is leveled, remove the perforated steel plate and grind it with a grinding wheel

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