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本文重点讨论磁力探伤检验发纹的工艺参数和与酸浸法检验发纹的关系。基本原理磁力探伤是用利磁性检查钢材的缺陷。当被检试件充磁时,磁力线沿着导磁率最大的方位分布。如试件存在缺陷(裂纹、发纹、白点、夹杂等等)时,则磁力线绕过缺陷向两侧拥挤,形成磁力线分布不均现象。假如缺陷暴露在表面或距表面很近时,则部份磁力线穿过试件表面,形成漏磁场,产生N-S极(图1)。这些小磁极对磁粉具有一定的吸附能力,因此就可以判断钢材是否有缺陷,并表示出缺陷的位置和形状。充磁电流的大小对检验结果影响很大。假定被充磁场的试件是圆形或近似圆形的,则试件被循环充磁时,表面产生的交变磁场强度与磁化电流的关系如下式:
This article focuses on magnetic testing of hairline process parameters and acid leaching method to test the relationship between the hairline. Fundamentals Magnetic inspection is the use of magnetic inspection of steel defects. When the test piece is magnetized, the lines of magnetic force are distributed along the direction of maximum magnetic permeability. If the specimen is defective (crack, hairline, white point, inclusions, etc.), then the magnetic field lines around the defect crowded to both sides, forming the phenomenon of uneven distribution of magnetic lines of force. If the defect is exposed on the surface or close to the surface, part of the magnetic lines of force pass through the surface of the specimen to form a leakage magnetic field, resulting in an N-S pole (Figure 1). These small magnetic particles have a certain adsorption capacity of the magnetic powder so that the steel can be judged as defective and indicate the position and shape of the defect. Magnetizing current size of the test results have a great impact. Assuming that the specimen to be magnetized is circular or nearly circular, the relation between the intensity of the alternating magnetic field generated on the surface and the magnetizing current when the specimen is cyclically magnetized is as follows: