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repairing effect. (1) Heated position and flame intensity: The effect of flame correction depends on the heated position and the flame intensity. Different heated spots bring about different effects, and the heated position - 800 ℃ ℃). (2) Heating ways normally adopted for flame correction in the vehicle body maintenance are: ① Spot heating: The heated area is a round spot of a certain diameter, which is usually 15 - 30mm. One or more spots can be heated according to the actual deformity situation. When ② Triangle heating: The heated area resembles a triangle, and this way is often used for correcting strip-shaped materials and deformed panel edges. ·
Expansion area Wavy edge Heating position Triangle heatin Fig. 11
Stretched Spot heating Fig. 1 0 (3) Cooling-contracting way: When the flame is taken away, proper cooling ways should be chosen according to the stretched degrees of the metal panels. Different cooling ways bring about different ① Natural cooling-contracting, or cooling in the air naturally, which is suitable for smaller areas of deformities. ② Water cooling, or covering the heated area with wet cotton cloth to make it cool suddenly. The contraction of metal plate cooled in this way is larger than that of the naturally cooled one, but ③ Natural cooling and hammering, usually operated with a hand hammer and a underlay iron. During the operation, beat around the heated area quickly to increase the compressing stress 4.3. Restoration of Cutting & Patching When any part of the metal door panel is eroded or damaged beyond repair, it should be removed and Procedures for cutting repair are as follows: (1) Check the damaged part and determine the repairing area. (2) Make a paper model according to the determined area. (3) Draw lines on the metal plates and cut material according to the paper model, and leave proper processing allowance. 61
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