The surface quality of 304 stainless steel plate is mainly determined by the pickling process after heat treatment. If the surface oxide scale formed by the previous heat treatment process is thick or the structure is uneven, pickling cannot improve the surface finish and uniformity. Therefore, sufficient attention should be paid to the heating of the heat treatment or the surface cleaning before the heat treatment.
If the thickness of the oxide scale on the surface of the stainless steel plate is not uniform, the surface finish of the base metal under the thick part and the thin part will also be different. Therefore, the surface of the steel sheet is uneven. Therefore, the oxide scale must be formed uniformly during the heat treatment. To meet this requirement, the following issues must be noted:
If the stainless steel plate is heated with oil on the surface of the workpiece, the thickness and composition of the scale of the oil-adhering part will be different from those of other parts, and carburization will occur. The carburized part of the base metal under the scale will be seriously affected by acid. erosion. The oil droplets ejected during the first combustion of the heavy oil burner will have a great impact if they adhere to the workpiece. It also affects when the operator's fingerprint is attached to the workpiece. Therefore, the bath maker can't directly touch the stainless steel parts with his hands, and don't make the workpieces stained with new oil. Clean gloves must be worn.
If there is lubricating oil on the surface of 304 stainless steel plate during cold working, it must be fully degreased with trichloroethylene degreaser and caustic soda solution, then washed with warm water, and then heat treated.
If there are sundries on the surface of the stainless steel plate, especially when organic matter or ashes are attached to the workpiece, heating will of course affect the oxide scale.
Differences in the atmosphere in the stainless steel plate furnace The atmosphere in the furnace is different in different parts, and the formation of oxide scale will also change, which is also the reason for the unevenness after pickling. Therefore, when heating, the atmosphere of each part of the furnace must be consistent. For this, the circulation of the atmosphere must also be considered.
In addition, if the bricks, asbestos, etc. that constitute the heating workpiece table contain moisture, the moisture will evaporate during the heating process, and the atmosphere of the part in direct contact with the steam will be different. In other parts, the formation of oxide skin will of course be different. Therefore, objects in direct contact with the heated workpiece must be sufficiently dry before use. However, if dried and left at room temperature, moisture will still condense on the surface of the workpiece in the presence of high humidity. Therefore, it is best to dry before use. If there is residual oxide scale on the part of the 304 stainless steel plate before heat treatment, and there is residual oxide scale on the part of the 304 stainless steel plate and the part without scale after heating, the thickness and composition of the scale will be different, resulting in uneven surface after pickling. Uniform, so pay attention not only to the final heat treatment, but also to the intermediate heat treatment and pickling.
There is a difference between the oxide scale produced on the stainless steel surface in direct contact with the gas or oil flame and without contact. Therefore, it is necessary to prevent the treatment member from directly contacting the flame port during the heating process.