Square pipe will show different problems in the manufacturing process, and the problems arising from different manufacturing methods are also different. We will adopt appropriate methods to deal with the problems, so as to ensure the normal use of Square pipe. The following is mainly about the quality defects of Square pipe after heat treatment. Common quality defects of square pipe after heat treatment are: quenching microstructures overheating, underheating, quenching cracks, insufficient hardness, heat treatment deion, surface decarbonization, soft point, etc.'They have important influence on the service life and accuracy of square pipe. Analyzing the causes of the ion of Juan has an important role in guiding the heat treatment process and prevention.
1. Square tube overheating:
从方管粗糙口上可观察到淬火后的显微组织过热情况。但i 要确切判断其过热的程度，必须观察显微组织。如果GCrl5钢的淬火组织中出现粗针状马氏体，则为淬火过热组织。形成原因可是淬火加热温度过高或加热保温时间太长造成的全面过热;也可肖巨是因原始组织带状碳化物严重，在两带之间的低碳区形成局部马氏体针状粗大，造成的局部过热。过热组织中残留奥氏体增多，尺寸稳定性下降。由于淬火组织过热，钢的晶体粗大·会导致方管的核J 性下降·抗冲击性能降低，方管的寿命也降低。过热严重甚至会造成淬火裂纹。
Overheating of quenched microstructures can be observed from the rough mouth of square tubes. However, in order to determine the degree of overheating, we must observe the microstructures. If coarse acicular martensite appears in the quenched structure of GCrl5 steel, it is quenched superheated structure. The reason is that the quenching heating temperature is too high or the heating holding time is too long, which results in the overall overheating. It can also be said that Xiao Ju is the local overheating caused by the ion of local martensite needle-like coarseness in the low-carbon zone between the two zones due to the serious ribbon carbides in the original structure. The retained austenite in the superheated structure increases and the dimensional stability decreases. Due to the overheating of quenched structure, the coarse crystal of steel will lead to the decrease of core J property, impact resistance and service life of square tube. The severe overheating may even cause quenching cracks. 2、方管热处理变形：
2. Heat treatment deion of square pipe:
There are thermal stress and organizational stress in square tube during heat treatment. The internal stress can be superimposed or partially offset each other, which is complex and changeable. Because it can change with the change of heating temperature, heating speed, cooling mode, cooling speed, shape and size of parts, and charging mode, the heat treatment deion of square tube is unavoidable. Understanding and mastering its changing law can make the deion of bearing parts (such as the ellipse of alloy tube, size expansion, etc.) in a controllable range, which is conducive to the normal production. Of course, mechanical collision in the heat treatment process will also cause deion of parts, but this deion can be reduced and avoided by improving operation.
3. Soft spot of square pipe:
The phenomenon that the local hardness of square tube surface is not enough due to insufficient heating, poor cooling or improper quenching operation is called quenching soft point. Like surface decarbonization, it can cause serious decrease in wear resistance and fatigue strength of the surface, which will cause severe local wear or failure during use.
We will make a deep study of the problems that occur in the heat treatment of square pipes, so that the quality assurance of square pipes can be reasonably utilized. After forming the square tube, we will carry out all-round inspection of the square tube, so that the quality of the square tube can be guaranteed and the customers can be satisfied in practical application. 标签:
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