1, brittleness is a common defect reed, can be divided into two kinds of hydrogen embrittlement after heat treatment and galvanizing brittle. Microscopic found there intergranular fracture of hydrogen embrittlement, dimple, secondary cracks, etc., it can also be observed in the fracture surface of the hairline and hydrogen micropores.
1) Heat treatment of brittle
Spring steel has a thermal sensitivity and tendency to temper brittleness, and its tempering temperature is often just in the first class and second class temper brittleness junction temper brittleness, if not timely tempering, heat and cooling, it will make spring sheet brittle.
Remedy: tempering temperature control, timely tempering, heat and cooling.
2) hydrogen embrittlement
After galvanizing easily lead reed fragility, because before galvanizing, pickling must be to remove the oxide scale, will lead to some of the hydrogen to penetrate the coating and the base metal, weakening the bonding metal crystal grain boundaries between atoms force and produce internal stress, brittle reed, the "hydrogen embrittlement."
Remedy: pickling time and temperature control, regulate galvanizing process, and galvanized, at a temperature of 180 ℃ heat for several hours then in addition to hydrogen technology, so that you can reduce the brittle reeds coating and organizations.
2, heat treatment crack
Generally caused by heat treatment reed cracks less likely, if cracks, the reason is: improper heat treatment process, tooling not debug properly, operator error and the like. Reed refers to improper heat treatment process heating temperature is too high, the holding time is too long, so that the spring in the organization austenite grain coarsening, thick needle martensite after quenching, resulting in stress and brittle reed increases, so the formation of heat cracks.
Remedy: use mesh belt furnace process reed, controlling the heating temperature of 790 ℃, control the holding time, direct oil quenching, tempering time after cleaning, can effectively solve the heat generated cracks reed.
