Magnesium balls can improve the strength and hardness through heat treatment. The following provides various heat treatment effects. For light burned magnesium balls, you can choose the appropriate heat treatment according to the situation. If you just want to increase the hardness, surface quenching is recommended. The purpose of normalizing ductile iron is to obtain the pearlite matrix structure, and to refine the grains and uniform structure to improve the mechanical properties of the casting. Sometimes normalizing is also the preparation for the surface quenching of ductile iron. Normalizing is divided into high temperature normalizing and low temperature normalizing. The high temperature normalizing temperature generally does not exceed 950～980℃, and the low temperature normalizing temperature is generally heated to the common bending temperature range of 820～860℃. After normalizing, four people are required to deal with it to eliminate the internal stress generated during normalizing.
In order to improve the mechanical properties of ductile iron, castings are generally heated to 30-50°C above Afc1 (Afc1 represents the final temperature of A formation during heating), and then quenched into oil to obtain a martensitic structure. In order to appropriately reduce the residual stress after quenching, tempering should generally be carried out after quenching. The low-temperature tempering structure is tempered martensite with residual bainite and nodular graphite. This structure has good wear resistance and is used for parts requiring high wear resistance and high strength. The tempering temperature of medium temperature is 350-500℃. After tempering, the structure is tempered troostite plus spherical graphite, which is suitable for thick parts that require good wear resistance, stability and elasticity. The high-temperature tempering temperature is 500-60D ℃, and the structure after tempering is tempered Soxhlet with spheroidal graphite, which has the comprehensive properties of good combination of toughness and strength, so it is widely used in production.
Ductile iron can obtain high strength after austempering, while having good plasticity and toughness. The selection of the heating temperature for multi-temperature quenching mainly considers that the original structure is completely A-formed, without residual F, and at the same time, avoiding the growth of A grains. The heating temperature is generally 30-50°C above Afc1, and the isothermal treatment temperature is 0-350°C to ensure that the lower bainite structure with comprehensive mechanical properties is obtained. Rare earth magnesium aluminum ductile iron after isothermal quenching σb=1200～1400MPa, αk=3～3.6J/cm2, HRC=47～51. But pay attention to adding a tempering process after austempering.