Cause analysis and solution of abnormal spring sheet hardness
2022-11-11
Cause analysis and solution of abnormal spring sheet hardness
Key Tips:
1. Brittleness is one of the common defects of reed, which can be divided into two kinds: brittleness after heat treatment and hydrogen brittleness after galvanized. It is found that the fracture of hydrogen embrittlement is intergranular, dimple, secondary crack, etc. On the fracture surface, it can be divided into two types: heat treatment embrittlement and galvanized hydrogen embrittlement.
2. Heat treatment brittleness: spring steel has a tendency of thermal sensitivity and tempering brittleness, and its fire temperature is usually just at the joint of the first type of tempering brittleness and the second type of tempering brittleness. If it cannot be timely tempered, insulated and cooled, it will make the reed brittle.
Solution: Control tempering temperature, tempering, heat preservation and cooling in time.
3. Hydrogen embrittlement
After hot galvanizing, it is easy to increase the brittleness of the reed. This is because before galvanizing, pickling must be carried out to remove the oxide skin, which will cause some hydrogen to infiltrate into the coating and collective metal, weaken the bonding force between crystal atoms and generate internal stress, which makes the reed brittle, namely "hydrogen embrittlement".
4. Heat treatment crack
Heat treatment generally leads to a small chance of reed cracks and defects, and the reasons are as follows: improper heat treatment process, improper tooling debugging, operator error, 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 structure coarser and the martensite needle coarser after quenching, leading to the increase of internal stress and brittleness of the reed, thus forming heat treatment cracks.
Solution: The mesh belt furnace is used to treat the reed, the heating temperature is controlled to 790 degrees, the holding time is controlled, the oil is quenched directly, and the tempering is timely after cleaning, which can effectively solve the heat treatment crack defects of the reed.
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