All kinds of defects caused by poor cutting are collectively referred to as cutting defects. When cutting small steel with flying shear in hot state, the scars with different depth and irregular shape on the steel surface are called cutting wounds; In the hot state, the surface is damaged by the saw blade, which is called sawing injury; After cutting, the cutting surface is not perpendicular to the longitudinal axis, which is called cutting inclination or sawing inclination; The cut head is short if the hot-rolled shrinkage part at the end of the rolled piece is not cut clean; After cold shearing, local small cracks appear on the shear surface, which is called tearing; After sawing (shearing), the metal flash left on the steel end face is called burr.
The sawing steel is not perpendicular to the saw blade (cutting edge) or the head of the rolled piece is bent too much; Equipment: the saw blade has a large curvature, the saw blade is worn or improperly installed, and the gap between the upper and lower blades is too large; Flying shear imbalance; Operation: too many steel pieces are cut (sawed) at the same time, too few ends are cut, the hot-rolled shrinkage part is not cut clean, and various misoperations.
Improve the incoming material condition, take measures to avoid excessive bending of the rolled piece head, and keep the incoming material direction perpendicular to the shear (SAW) cutting plane; Improve the condition of the equipment, adopt the saw blade without bending or with small bending degree, properly select the thickness of the saw blade, replace the saw blade (cutting edge) in time when it is worn, and correctly install and adjust the cutting (sawing) equipment; Strengthen the operation, and do not cut too many pieces at the same time to avoid the rise and fall and bending of steel. The necessary end cutting amount must be ensured to cut the hot-rolled shrinkage part completely to avoid various misoperations.
Section steel correction marks -- surface scars caused in the process of cold correction. This kind of defect has no trace of hot working and has a certain regularity. There are three main types. Pit type (or correction pit), fish scale type, damaged type.
The pass of the straightening roll is too shallow, the steel is seriously bent before straightening, the steel feeding is not correct during straightening or the straightening machine is adjusted improperly, which can cause damage to the straightening mark; The local damage of the straightening roll or the bonding metal block, the local bulge of the roll surface, the serious wear of the straightening roll or the high temperature of the roll surface, and the bonding metal can produce fish scale correction marks on the steel surface.
Jinan section steel gives you reference control methods
Do not continue to use the straightening roll when it is seriously worn and has serious straightening marks; When the straightening roll is locally damaged or bonded with metal blocks, it should be polished and polished in time; When straightening steel sections such as angle steel, due to the relatively large movement of the contact surface between the straightening roll and the steel (caused by the linear speed difference), it is easy to raise the temperature of the straightening roll and scrape the tumor, resulting in straightening marks on the steel surface, so the surface of the straightening roll should be poured with cooling water for cooling; Improve the material of straightening roll or quench the straightening surface to improve the surface hardness and wear resistance.
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