Metal welding development

Historical development of the history of metal welded connection can be traced back thousands of years ago, early in welding technology is the Bronze Age and Iron Age in Europe and the Middle East discovery.

On the one hand, these two metals are connected to each other by bolts or physical connections, which appears as a strong metal as a whole, but the connection is discontinuous, and sometimes the metal surface has an oxide insulating film, or even correct or wrong physical contact. Welding is the process of fusing two metals. The soldering process usually includes: 1) melting of the flux, thereby removing the oxide film on the surface of the metal to be soldered; 2) melting the solder, so that the luminous flux suspended between the impure material and the solder floats on the surface; 3) some metals connected to the solder Dissolve; cool and complete the melting of the metal and solder.

Selection of welding wire The selection of welding wire should be based on the type of welding steel , the quality requirements of welding parts, welding conditions (thickness, groove shape, welding position, welding conditions, post-weld heat treatment and welding operations, etc.) and cost. The order of selecting conductors for consideration is as follows: 1. Welding wires are selected according to the steel types of carbon steel and low-alloy high-strength steel welding structures, and welding wires that meet mechanical properties are mainly selected according to the principle of "equal strength matching". For heat-resistant steel and weather-resistant steel, the main consideration is the similarity of the chemical composition of the weld metal and the base metal to meet the requirements of heat resistance and corrosion resistance. 2According to the quality requirements of the welded parts (especially impact toughness), according to the choice of welding wire welding conditions, the shape of the groove, the mixing ratio of the shielding gas, etc., and the maximum welding efficiency and reducing the selection to ensure the performance of the welded joint. Welding process performance includes arc stability, size and number of spatter particles, slag removal, weld appearance and shape. For the welding of carbon steel and low alloy steel (especially semi-automatic welding), the welding method and welding material are mainly selected according to the welding process performance.

However, as engineers continued to improve the metal coating technology (i.e., flux) on the electrode surface in the 20th century, the new electrode can provide a more stable arc and effectively isolate base metals and impurities, therefore, arc welding can gradually replace combustible Gas welding has become the most widely used industrial welding technology.

Precautions for welding arc length The length of the arc is related to the type of electrode coating and the thickness of the coating. Short arc can prevent harmful gases such as O2 and N2 in the atmosphere from invading the weld metal. The welding speed is appropriate. The welding speed has a corresponding change under the conditions of electrode diameter, coating type, welding current, heat capacity of the object to be welded, structure, standard, etc , Cannot be specified. Maintain a suitable welding speed, the slag can cover the molten pool well.