Hot-dip galvanized sheets are mainly used in construction, home appliances, automobiles, machinery, electronics, light industry and other industries.
Commonly used steel types of hot-dip galvanized sheets include: general commercial coil (CQ), structural galvanized sheet (HSLA), stamped galvanized sheet (DQ), deep-drawing hot-dip galvanized sheet (DDQ), and bake-hardened hot-dip galvanized sheet (BH), dual phase steel (DP), TRIP steel (transformation induced plasticity steel), etc.
There are three types of galvanizing annealing furnaces: vertical annealing furnace, horizontal annealing furnace and vertical and horizontal annealing furnace.
Generally, there are two cooling methods for hot-dip galvanized sheet cooling towers: air cooling and water cooling.
Strain age embrittlement in the case of cracks
Hotspot issues often involve a variety of problems, such as cracked welds, cracked materials, etc., and users often don't know what's going on. In fact, heat treatment can also cause cracking because the material becomes "brittle" during the heating process. In the most typical case, with perforated components, the steel cracks along the location of the perforation during hot-dip galvanizing:
This kind of cracks that appear in the perforations or edges of galvanized steel sheets are strain-aging brittle cracks during hot-dip galvanizing.
Cracks in galvanized steel sheets Cracks in galvanized steel profiles
Causes of strain age cracking
During the galvanizing process, strain aging fracture may occur in two situations:
Stress must be "introduced" before galvanizing. Cold working operations such as punching, grooving, shearing and severe bending can create "stresses" within the steel. If stress relief is not performed prior to galvanizing, the stresses introduced into the material during the galvanizing process will translate into high localized residual stresses and lead to strain-age brittleness.
Strain-age brittleness can also be caused by inclusions in the steel. For example, some poorer quality steels (such as ground steel) used in steel bars can undergo brittle fracture when bent at the processing site.
Bending or repeated bending of galvanized steel sheets with smaller core radii during blanking of thicker sections can result in increased cold working stresses. If the part cracks due to strain aging, this cracking usually occurs directly after hot-dip, but for steel bars, it can also occur at the construction site, and the stress caused by even simple handling is enough to cause tension. Aging brittleness.
Cracks will appear in the steel shortly after hot plating is completed, which is the biggest difference between strain age brittleness and hydrogen embrittlement.
