Control Measures of Brittleness and Heat Treatment Cracks in Spring Steel Reeds

1. Brittleness is one of the common defects of reeds. It can be divided into heat brittleness and hydrogen embrittlement after galvanizing. The microscopically discovered fractures of hydrogen embrittlement have intergranular, dimples, and secondary cracks. Hairline and hydrogen micropores can also be observed on the fracture surface.

1) Heat treatment brittleness

Spring steel has a tendency of thermal sensitivity and temper brittleness, and its tempering temperature is often just at the first temper brittleness and the second temper brittleness. If it cannot be tempered, kept warm and cooled, it will make the spring. The piece produces brittleness.

Remedy: Control tempering temperature, timely tempering, insulation and cooling.

2) Hydrogen embrittlement

Hot-dip galvanizing tends to increase the brittleness of the reeds. This is because before the galvanizing, pickling must be carried out to remove the oxide scales, which will cause a part of the hydrogen to infiltrate the coating and the matrix metal, weakening the bond between the metal crystal atoms on the grain boundary. Force and produce internal stress, make the reed become brittle, that is "hydrogen embrittlement."

Solution: Control the pickling time and temperature, standardize the galvanizing process, and after galvanizing, incubate for several hours at a temperature of 180°C and then carry out the dehydrogenation process. This will reduce the plating and the brittleness of the reed.

2, heat treatment crack

The heat treatment generally causes a small probability of reed crack defects. If cracks occur, the causes are: improper heat treatment process, improper tooling, and operator error. Improper heat treatment process means that the reed heating temperature is too high, holding time is too long, making the austenite grains in the reed tissue coarsening, martensite needle after quenching, resulting in increased stress and brittleness of the reed, thus Heat treatment cracks are formed.

Solution: Mesh furnace treatment reed, control the heating temperature of 790 °C, control the heat preservation time, direct oil quenching, timely tempering after cleaning, you can effectively solve the reed heat cracking defects.