Stainless steel seamless pipe surface inspection: The quality of stainless steel seamless pipe inspection is mainly determined by the pickling process after heat treatment. If the surface oxide skin caused by the previous heat treatment process is thick or the structure is uneven, pickling It does not improve the surface finish and uniformity. Therefore, we must pay full attention to the heating of heat treatment or the surface cleaning before heat treatment. If the thickness of the oxide skin on the surface of the stainless steel seamless pipe is uneven, the surface finish of the base metal under the thick place and the thin place is also different, and the surface oxide scale is dissolved during pickling and the base metal at the scale attachment site is acidified The degree of corrosion is different, so the surface of the seamless steel pipe is not uniform. Therefore, when heating in heat treatment, it is necessary to make it evenly form oxide skin. To meet this requirement, we must pay attention to the following problems: If oil is attached to the surface of the workpiece when the stainless steel seamless pipe is heated, the thickness of the oxide scale at the oil attachment part is different from the thickness and composition of the oxide scale in other parts, and carburization will occur. The carburized part of the base metal under the oxide skin will be severely attacked by acid. The oil droplets sprayed out when the heavy oil burner burns at the beginning, if attached to the workpiece, will have a great impact. It will also have an impact when the operator's fingerprints are attached to the workpiece. Therefore, the bath operator should not directly touch the stainless steel parts with his hands, and do not allow the workpiece to be stained with new oil. Clean gloves must be worn.
If there is lubricating oil attached to the surface of the stainless steel seamless pipe workpiece during cold processing, it must be fully degreased in trichlorethylene degreasing agent and caustic soda solution, then washed with warm water, and then heat treated. If there are sundries on the surface of the stainless steel pipe, especially when organic matter or ash adheres to the workpiece, heating will certainly affect the scale. The difference in the atmosphere in the stainless steel pipe furnace is that the atmosphere in the furnace is different in various parts, and the formation of oxide skin will also change, which is also the reason for the unevenness after pickling. Therefore, when heating, the atmosphere in each part of the furnace must be the same. For this reason, the cycle of air must also be considered. In addition, if the bricks, asbestos, etc. that make up the platform used to heat the workpiece contain water, the water will evaporate when heated, and the air in the part that is directly in contact with water vapor will be different from other parts, and the formation of oxide scales will of course also occur. Just disagree. Therefore, objects that are in direct contact with the heated workpiece must be fully dried before they can be used. However, if it is placed at room temperature after drying, moisture will still condense on the surface of the workpiece in an environment with high humidity. Therefore, it is best to dry it before use.
If the part of the stainless steel seamless pipe has residual scale before heat treatment, after heating, there will be a difference in the thickness and composition of the scale between the part with residual scale and the part without scale, which will cause the corrosion after pickling. The surface is uneven, so not only the final heat treatment must be paid attention to, but also the intermediate heat treatment and pickling should be fully paid attention to. There is a difference in the oxide scale that occurs on the surface of the stainless steel that is in direct contact with the gas or oil flame and where it is not in contact. Therefore, it is necessary to keep the treatment part from directly contacting the flame port when heating.