Precautions In Repairing High Strength Steel
Precautions In Repairing High Strength SteelHigh strength steel is used for body panels in order to reduce vehicle weight.
Accordingly, precautions in repairing automotive bodies made of high strength steel are described.
HIGH STRENGTH STEEL (HSS) USED IN NISSAN VEHICLES
Read the Following Precautions When Repairing HSS:
1. Additional points to consider
- The repair of reinforcements (such as side members) by heating is not recommended since it may weaken the component. When heating is unavoidable, do not heat HSS parts above 550 degrees C (1,022 degrees F).
Verify heating temperature with a thermometer.
(Crayon-type and other similar type thermometer are appropriate.)
- When straightening body panels, use caution in pulling any HSS panel. Because HSS is very strong, pulling may cause deformation in adjacent portions of the body. In this case, increase the number of measuring points, and carefully pull the HSS panel.
- When cutting HSS panels, avoid gas (torch) cutting if possible. Instead, use a saw to avoid weakening surrounding areas due to heat. If gas (torch) cutting is unavoidable, allow a minimum margin of 50 mm (1.97 in).
- When welding HSS panels, use spot welding whenever possible in order to minimize weakening surrounding areas due to heat.
If spot welding is impossible, use M.I.G. welding. Do not use gas (torch) welding because it is inferior in welding strength.
- The spot weld on HSS panels is harder than that of an ordinary steel panel.
Therefore, when cutting spot welds on a HSS panel, use a low speed high torque drill (1,000 to 1,200 rpm) to increase drill bit durability and facilitate the operation.
2. Precautions in spot welding HSS
This work should be performed under standard working conditions. Always note the following when spot welding HSS:
- The electrode tip diameter must be sized properly according to the metal thickness.
- The panel surfaces must fit flush to each other, leaving no gaps.
Rear fender hemming process
1. A wheel arch is to be installed and hemmed over left and right outer wheel house.
2. In order to hem the wheel arch, it is necessary to repair any damaged or defaced parts around outer wheel house.
CAUTION: Ensure that the area that is to be glued around outer wheelhouse is undamaged or defaced.
Procedure of the hemming process
- Peel off old bonding material on the surface of outer wheelhouse and clean thoroughly.
- Peel off a primer coat in the specified area where new adhesive is to be applied on rear fender (the replacing part).
- Apply new adhesive to both specified areas of outer wheelhouse and rear fender.
- Attach rear fender to the body of the car, and weld the required part except the hemming part.
- Bend the welded part starting from the center of the wheel arch gradually with a hammer and a dolly. (Also hem the end of the flange.)
- Hemming with a hammer is conducted to an approximate angle of 80 degrees.
- Starting from the center, hem the wheel arch gradually, using slight back and forth motion with a hemming tool.
- Seal up the area around the hemmed end of the flange.