In the production of stainless steel strips, the following heat treatment methods are commonly used:
(1) Quenching, for stainless steel, quenching is a softening heat treatment operation.
In order to remove the marks of the hot rolling process, the strip must be quenched. The quenching operation is to first heat the strip steel in the straight-through furnace, the general heating temperature is 1050 ~ 1150℃, so that the carbide in the steel is fully dissolved and the uniform austenitic structure is obtained. It is then cooled quickly, mostly by water. If it is cooled slowly after heating, it is possible to precipitate carbides from the solid solution in the temperature range of 900 ~ 1450℃, making the stainless steel sensitive to intergranular corrosion.
In the production of stainless steel strips, the following heat treatment methods are commonly used:
(1) Quenching, for stainless steel, quenching is a softening heat treatment operation.
In order to remove the marks of the hot rolling process, the strip must be quenched. The quenching operation is to first heat the strip steel in the straight-through furnace, the general heating temperature is 1050 ~ 1150℃, so that the carbide in the steel is fully dissolved and the uniform austenitic structure is obtained. It is then cooled quickly, mostly by water. If it is cooled slowly after heating, it is possible to precipitate carbides from the solid solution in the temperature range of 900 ~ 1450℃, making the stainless steel sensitive to intergranular corrosion.
The quenching of cold rolled stainless steel strip can be used as both intermediate and final heat treatment. As the final heat treatment, the heating temperature should be within the temperature range of 1100 ~ 1150℃.
Stainless steel strip heat treatment defects are:
(1) Gas corrosion is a small pit with black spots on the surface of the strip steel. If the emulsion, oil, salt, dirt and other remnants on the surface of the strip are not removed, the partial surface or all the surface of the strip (in the furnace for a long time) will be subjected to gas corrosion. At high temperature, gas corrosion on strip steel surface is more serious.
(2) overheating, overheating when the strip surface is dark brown, the surface layer of oxide iron sheet has been peeled off, but not easy to acid clean. The reason for this defect is that the metal is heated at a high temperature or stays in the furnace for a long time. Overheating may cause intergranular corrosion.
(3) Underheat, underheat strip surface has light gray metallic luster. The iron sheet is difficult to wash off during pickling, and the strip is gray after pickling. Underheat is caused by low heating temperature or too fast speed of strip through the furnace.
(4) Injury. Injury refers to the black punctate pits on the lower surface of the strip steel, which are easy to see after pickling. This defect is a small bulge on the working surface of the supporting roller table and damage the strip surface. For this reason, the furnace roller must be polished and replaced regularly.
Stainless steel strip heat treatment defects are:
(1) Gas corrosion is a small pit with black spots on the surface of the strip steel. If the emulsion, oil, salt, dirt and other remnants on the surface of the strip are not removed, the partial surface or all the surface of the strip (in the furnace for a long time) will be subjected to gas corrosion. At high temperature, gas corrosion on strip steel surface is more serious.
(2) overheating, overheating when the strip surface is dark brown, the surface layer of oxide iron sheet has been peeled off, but not easy to acid clean. The reason for this defect is that the metal is heated at a high temperature or stays in the furnace for a long time. Overheating may cause intergranular corrosion.
(3) Underheat, underheat strip surface has light gray metallic luster. The iron sheet is difficult to wash off during pickling, and the strip is gray after pickling. Underheat is caused by low heating temperature or too fast speed of strip through the furnace.
(4) Injury. Injury refers to the black punctate pits on the lower surface of the strip steel, which are easy to see after pickling. This defect is a small bulge on the working surface of the supporting roller table and damage the strip surface. For this reason, the furnace roller must be polished and replaced regularly.
Post time: Mar-31-2023