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中频感应加热弯管时,因工艺不当,材料的受拉面会产生组织松弛损伤,这是一种极其微细的晶界裂纹。其裂纹两端尖细呈曲线状,长约0.005～0.03毫米,均与拉力方向垂直(图1)。组织松弛损伤是材料脆化的一种形式,它使常温α_K、σ_s、σ_b值比中性区低。上述裂纹由于细微,常与晶界混为一体,一股的抛光侵蚀不易显现。分辨这种晶界裂纹,试样必须采用多次抛光、侵蚀法。一般低合金的侵蚀剂为:盐酸7毫升;苦味酸5克;乙醇100毫升(合金元素较高
IF induction heating pipe, due to improper technology, the material will be subject to the tensile surface of tissue relaxation injury, which is a very fine grain boundary crack. The tip of the crack tip is curved, about 0.005 ~ 0.03 mm, are perpendicular to the direction of tension (Figure 1). Tissue relaxation damage is a form of material embrittlement, which makes room temperature α_K, σ_s, σ_b value lower than the neutral zone. The cracks due to subtle, often mixed with the grain boundaries, an erosion is not easy to show. To distinguish this grain boundary crack, the sample must use multiple polishing, erosion method. The general low-alloy etchant: hydrochloric acid 7 ml; picric acid 5 grams; ethanol 100 ml (alloying elements higher