Spot welding is a resistance welding method in which welding parts are assembled into lap joints and pressed between two electrodes, and the base metal is melted by resistance heat to form a welding spot.
Spot welding can be divided into single spot welding and multi spot welding.Multiple spot welding is the welding of two or more solders with two or more pairs of electrodes simultaneously or according to the automatic control program.Spot welding is an efficient, economical and important connection method. It is especially suitable for stamping or rolling laminated components without air tightness and with thickness less than 3 mm.
Spot welding is mainly used in the following aspects:
(1) lap joint of sheet stamping parts, such as automobile cab, carriage, fish scale screen of harvester, etc.
(2) thin plate and shaped steel frame slimming and skin structure, such as side wall and roof of the carriage, drawing-carriage plate, hopper of combine harvester, etc.
(3) screen and space frame and cross reinforcement, etc.
Characteristics of the spot welding
During spot welding, the welding parts form lap joints and are pressed between the two electrodes. The main features are as follows:
(1) during spot welding, the heating time for the connection area is very short and the welding speed is fast.
(2) spot welding only consumes electrical energy and does not require filler material, flux, gas, etc.
(3) spot welding quality is mainly guaranteed by spot welding machine.Simple operation, high degree of mechanization and automation, high productivity.
(4) low labor intensity and good working conditions.
(5) because welding is completed in a very short time, need to use a large current and pressure, so the process of the program control is more complex, welding machine capacity, the price of higher equipment.
(6) it is difficult to conduct nondestructive inspection of solder joints.
To clean the workpiece surface before welding, the commonly used removal therapy is pickling removal, that is, pickling in the heated concentration of 10% sulfuric acid, and then washing in hot water.The specific welding process is as follows:
(1) feed the workpiece joint into the upper and lower electrodes of the spot welder and clamp them together;
(2) electrify, make the contact surface of two workpieces heated, partial melting, forming melting core;
(3) maintain the pressure after power off to make the molten core cool and solidify under the action of pressure to form solder joints;
(4) remove the pressure and remove the workpiece.