Control measures for brittleness and heat treatment cracks of spring steel reed

Control measures for brittleness and heat treatment cracks of spring steel reed

1, brittleness is one of the common shortcomings of the reed, which can be divided into two kinds of heat treatment brittleness and hydrogen embrittlement after galvanized. It is found that the fracture of hydrogen embrittlement has intergranular, dimple, secondary cracks, etc., and hair lines and hydrogen micropores can also be observed on the cracking surface.

1) Heat treatment brittleness

Spring steel has thermal sensitivity and tempering brittleness tendency, and its tempering temperature is often just in the first type of tempering brittleness and the second type of tempering brittleness, assuming that it can not be tempered in time, keep warm and cool, it will make the spring brittle.

Treatment method: Control the tempering temperature, tempering in time, keep warm and cool.

2) Hydrogen embrittlement

After hot-dip galvanizing, the brittleness of the reed is easily increased, which is because before galvanizing, it must be pickling to remove the oxide, which will cause a part of hydrogen to enter the coating and the base metal, weaken the binding force between the metal crystal atoms on the grain boundary and occur internal stress, making the reed brittle, that is, "hydrogen brittle".

Treatment method: Control the pickling time and temperature, standardize the galvanizing process, and after galvanizing, hold heat at 180℃ for several hours and then carry out the hydrogen removal process, so as to reduce the coating of the reed and the brittleness of the arrangement.

2, heat treatment crack

Heat treatment generally forms a small probability of reed cracks, if cracks occur, the cause is: improper heat treatment process, tooling is not properly adjusted, operator mistakes, etc. Improper heat treatment process means that the heating temperature of the reed is too high and the holding time is too long, which makes the austenite grain in the reed arrangement coarser, and the martensite needle is coarse after quenching, resulting in the increase of internal stress and brittleness of the reed, and then the formation of heat treatment cracks.

Treatment method: The mesh belt furnace is used to treat the reed, the heating temperature is controlled to 790℃, the holding time is controlled, the oil quenching is direct, and the tempering is timely after cleaning, which can effectively deal with the shortcomings of the heat treatment cracks occurring in the reed.