Non-destructive testing refers to a method of detecting macroscopic defects on the surface or inside of castings and materials under test conditions that do not damage them.

The main purpose of solution treatment is to dissolve carbides or other precipitated phases in solid solution to obtain a supersaturated single-phase structure.

Tempering refers to a heat treatment process in which the quenched or normalized steel castings are heated to a selected temperature lower than the critical point Ac1, and after holding for a period of time, they are cooled at an appropriate rate.

Quenching is a heat treatment process in which steel castings are heated to a temperature above Ac3 or Ac1, and then rapidly cooled after holding for a period of time to obtain a complete martensitic structure.

Normalizing is a heat treatment in which the steel is heated to 30 °C - 50 °C above Ac3 (hypoeutectoid steel) and Acm (hypereutectoid steel), and after a period of heat preservation, it is cooled to room temperature in air or in forced air method.

According to different heating methods, holding time and cooling conditions, the heat treatment methods of steel castings mainly include annealing, normalizing, quenching, tempering, solution treatment, precipitation hardening, stress relief treatment and hydrogen removal treatment.

The heat treatment of steel castings is based on the Fe-Fe3C phase diagram to control the microstructure of the steel castings to achieve the required performance.

During the test of mechanical properties of castings, the hardness is always required by the end users or customers. Due to different materials and casting processes, the required number of hardness is covered from a wide range.

For the lost foam casting process, the carbon-increasing defect of steel castings is a difficult problem. Carburization means that the carbon content in steel castings will be higher than expected after casting.

Because gray iron castings have many advantages, it is widely used in many industrial and mechanical fields. In this article, we have cited examples of working conditions and uses of different grades of gray cast iron.

generally speaking the cast steel castings always costs higher than the iron castings. This situation caused mainly by two factors. The first is the cast steel materials is more expensive, especially the steel alloys or even the stainless steel. If the customers require special mechanical properties like wear-resistance, heat-resistance or anti-rust performance, the special chemicals (such as Mn, Mo, Cr, Ni) should be added into the molten metal during casting.

Cast iron includes gray iron, ductile iron (nodular), white iron, compacted graphite iron and malleable iron. Gray iron is cheaper than ductile iron, but it has much lower tensile strength and ductility than ductile iron. Gray iron can not replace the carbon steel, while the ductile iron could replace the carbon steel in some situation due the high tensile strength, yield strength and elongation of ductile iron.