The deformed places of the panels are straightened, as a rule, manually using a special tool (metal, plastic, wooden hammers and various mandrels) and fixtures.
Heated straightening is used for upsetting (contractions) highly stretched panel surfaces. To prevent sharp swelling and deterioration of the mechanical properties of the panel, it is heated to 600-650°C (cherry red color). The diameter of the heated spot should be no more than 20-30 mm.
To tighten surfaces, proceed as follows:
- with a carbon electrode of a semi-automatic welding machine or a gas burner, heat the metal from the periphery to the center of the defective area and, with the blows of a wooden mallet and hammer, upset the heated places using a flat support or anvil;
- repeat the heating and upsetting operations until the desired panel surface is obtained.
Irregularities in the panels can be smoothed out with polyester fillers, thermoplastics, cold curing epoxy putties and soldering.
Polyester putty type «Chempropol-P» or PE-0085 form reliable connections with panels cleaned to metal. They are two-component materials: an unsaturated polyester resin and a hardener, which is a catalyst for the rapid curing of the mixture. The temperature in the working room should not be below 18°C. The prepared polyester putty must be used in no more than 10 minutes. It finally hardens 60 minutes after application. The thickness of the putty layer should not exceed 2 mm.
The thermoplastic is available in powder form. Elastic properties necessary for applying it to the metal surface of the panel, it acquires at a temperature of 150-160°C. The surface to be filled must be thoroughly cleaned of rust, scale, old paint and other contaminants. Thermoplastic adhesion is better to rough metal surfaces. To apply thermoplastic, the area to be leveled is heated to 170-180°C and the first layer of powder is applied, which is rolled down with a metal roller. Then a second layer is applied and so on, until the unevenness is filled. Each layer is rolled to obtain a monolithic layer of plastic mass. After hardening, the layer is processed by conventional methods.
Solders such as POSSu 18-2 or POSSu 25-2 are used to level areas previously filled with solder, build up the edges of parts and eliminate gaps.
In case of significant damage, the panels are replaced with new ones using electric welding in a protective gas environment.