1.What are the overall principles of correction?
The general principle for correction is to try mechanical correction first. If this is ineffective or impossible, then consider thermal correction. Extreme caution should be exercised during thermal correction.
Before beginning any correction procedure, be sure to take appropriate personal protective measures:
Forced ventilation: Avoid inhaling zinc fumes (which can cause "metal fume sickness").
Goggles and a protective mask.
Fire-resistant gloves.
2.What are the steps for mechanical correction?
Press/Hydraulic Press Correction:
Suitable for: Large areas of bulging or bending.
How to: Place the workpiece on the press table with the convex surface facing up. Place a flat block (softer than the workpiece, such as copper or aluminum) between the pressure point and the workpiece to prevent damage to the zinc layer. Then, slowly apply pressure until the surface is flat again. This may require multiple pressure applications at multiple points, along with measurement.
Roller/Leveler Correction:
Suitable for: Longitudinal bends or wavy edges on long sheets.
How to: Pass the welded workpiece through the leveler rollers multiple times, using the pressure to flatten the workpiece. This is the most professional and effective method, but requires specialized equipment.
3.What are the steps for spot heating?
Place the workpiece with the convex surface facing up.
Use an oxyacetylene flame or a small welding torch to quickly and locally heat the highest point of the raised area. The heated spot should be approximately 10-20mm in diameter, with a spacing of 50-150mm between each spot.
Key: Strict temperature control! Ideally, the heating temperature should be between 200-300°C (just enough to see a slight dark red hue on the steel plate, not too bright). Excessive temperatures will completely burn away the zinc layer.
After heating, immediately cool the area around the heated spot with a damp cloth or sponge. (Avoid directly cooling the center of the heated spot, as this will cause the zinc layer to crack.) The metal at the heated spot will contract as it cools, flattening the surrounding metal.
4.What is the operation method of linear heating?
Use the welding torch to heat the weld rapidly in a straight line along the back of the weld or along the curved ridge, and then cool both sides of the line with a wet cloth.
5.What are the precautions for thermal correction?
Zinc layer damage: The zinc layer in the heated area will almost certainly be damaged, requiring subsequent zinc replenishment and rust prevention treatment (such as spraying zinc-rich paint or cold-dip galvanizing).
Highly technical: Improper control of heating position, temperature, and speed may cause new and more complex deformations.