In steel ingot solidification process, as a result of intergranular part of low melting point material last solidification shrinkage and gas gap, and not match welded pipe in hot working process. Segregation in the steel, mild, high level of osteoporosis can be allowed to exist.
Inclusion: mixed mixed metal and nonmetallic inclusions. Metal inclusions: mainly casting process, the metal strip, sheet, block ingot mould is accidentally fall into or join late in smelting ferroalloy Precision steel tubes piece not defects, formed by the fusion of sample in low power, more show Now the edge is clear, color with the surrounding significantly different geometric shapes. Non-metallic inclusions: in the process of casting, no time to slag or peeling off into the molten steel lining and refractory materials for the inner surface of gating system, non-metallic inclusion is very large Good recognition, and smaller mixed corrosion after peeling, leaving small circular holes.
Shrinkage cavity: on the low sample, shrinkage cavity is located in the center, the surrounding is often the place of segregation, inclusion, or loose dense, sometimes can see caves or gap in front of the corrosion. Corrosion cavity part after dark, irregular fold holes. Reasons for the formation: ingot casting, the last part of the solidification (heart) liquid steel solidification shrinkage is not filled at the legacy of macro cavity, shrinkage cavity mainly formed in the ingot head end (cap).
Bubble: in the low power on the sample, is roughly the vertical cracks and surface, just nearby With oxidation and decarburization phenomenon, below the surface of the position of the subcutaneous bubbles, deep subcutaneous bubble called pore. Reasons: ingot casting process and release of gas produced by crack Precision Welded pipes defects caused by: on the low power sample, axis Position along the intergranular cracking, into a spider, serious when radiated cracking.
Reasons: the main is two kinds, one kind is ingot during solidification cooling, for some reason and the internal tear, in the process of forging rolling not welded; Another is due to the forging Made of internal crack.
White: on low-power sample are thin short cracks, generally concentrated in the interior of the steel, the thickness of about 20 to 30 mm in the surface layer almost no, because crack is not easy to distinguish, fracture test should be done for validation. White spots in the broken Shown on the mouth for coarse grain of silver white. Reasons: is thought to be hydrogen and stress the role of the organization, is hydrogen gas chromatography were set off to loose a huge pressure in the pores and phase transformation in steel produced by the local stresses in the joint of tiny cracks.
Defects, shape size 1, the size of three poor: including the length, diameter and thickness of the steel, plus or minus tolerance, grinding depth, width, etc Do not conform to the requirements of the order of standard size.
Ovality: refers to the circular cross section of the steel stainless steel 304 pipes cross section on the difference between the maximum minimum diameter. Bending: steel in length and width direction is not straight, the degree of curvature of different materials have different names, profile expressed in bending;
Plate, belt is expressed as a rocker, wave bending curvature, gone with the wind. Turn: the axial twisted into a spiral steel bar.