The influencing factors on the furnace tube welding seam quality
Sources: this site Click: Date: 2015-8-12 17:48:56
Furnace is a kind of pressure welding, welding temperature and pressure are the main factors influencing the welding quality.And welding temperature and pressure by the steel chemical composition, heating temperature, state of the edges of the strip and the factors of forming roll pass design.
The chemical composition of the pipe not only decide the possibility of pressure welding, and limiting factors of heating temperature.Practice has proved that carbon content is more than 0.3% ~ 0.5%, the welding temperature with the increase of carbon content and lower;When carbon content less than 0.3% ~ 0.5%, pressure weld strength increased with the increase of carbon content increased.This is because the smaller docking furnace welding when the welding pressure, pressure alone cannot obtain a good weld, also the pipe must be heated to close to the melting temperature, to get good weld, ensure enough strength.When carbon content more than 0.3% ~ 0.5%, the heating temperature before welding and welding temperature significantly narrowed down, combined with the carbon content increased after metal carbides increased in crystallization, the atomic diffusion speed slow, difficult to form a common grain, thereby reducing the quality of the weld.Therefore, the furnace pipe welded pipe used in carbon content are controlled under 0.3% ~ 0.5%.The characteristics of rimming steel segregation, the chemical composition of the tube billet edges on both sides there is a big difference.Segregation of billet in heating furnace, there is no guarantee that tube billet two edge and center part of the requirements of different temperature, the side of carbon and sulfur and other impurities, will the abscission layer due to temperature stress and the welding pressure, heating temperature is too low, the welding.
The existence of chromium, nickel and non-ferrous metals, edge causes dense oxide, welding difficulties caused by the diffusion speed slow.
The wind wash also is one of the factors that affect the weld quality.Because the wind wash (blowing) can not only off the edge of slag and iron oxide, improve the edge metal purity, but also can make the temperature of 50 ~ 80 DHS C, formation of weld metal is very common crystallization.Therefore, wind pressure and wind speed, the structure of ram shape and Angle of the jet are correct or not will affect the quality of the weld.
In addition, on the edge of the tube billet edges, burrs, scarring, and shrinkage cavity defects can cause burning, wave bending and other waste.
Ensure the tube billet geometry and dimensional accuracy of precise pressure forming and welding machine right groove design and selection of pressure in different extent, also affect the quality of welded pipe.
