Causes of Wear of Steel Casting Parts and Precautions for Repairing Defects

Ⅰ. What are the factors that affect the wear of steel casting parts?

Wear is the main failure mode of steel casting parts, especially in abrasive wear conditions. Due to the strong influence of abrasive and other working conditions, wear-resistant cast steel materials gradually lose and eventually fail. So what are the factors that affect the wear of steel casting parts?

The hardness of steel casting parts is an important factor affecting its wear. Generally speaking, it is hoped that the hardness of wear-resistant parts is more than 0.8 times higher than that of abrasives to obtain better wear resistance.

It must be specially stated that the hardness of the wear-resistant parts is the hardness of the working surface of the wear-resistant parts after wear, not the initial hardness before wear. However, the hardness of wear-resistant parts is not as high as possible. In some working conditions, too high hardness is easy to cause micro-cracks.

For the abrasive wear of micro-cutting mechanism, increasing the hardness of steel casting parts is beneficial to the improvement of wear resistance.

For abrasive wear by fatigue spalling mechanism, the higher hardness of steel casting parts is combined with good ductility and toughness, especially with good fracture toughness, low crack growth rate and high impact fatigue resistance. Conducive to the improvement of wear resistance.

If steel casting parts are used in high temperature or wet abrasive wear conditions, due to high temperature oxidative corrosion or electrochemical corrosion, the wear parts are subjected to both abrasive wear and corrosive wear, which is corrosive abrasive wear.

In addition to the above-mentioned mechanical property requirements for abrasive wear, for high temperature wear, improving the oxidation resistance of steel casting products, such as increasing the Cr content, will help improve wear resistance;

For wet corrosion wear, increasing the electrode potential of steel casting parts, especially reducing phase boundary corrosion, will be beneficial to the improvement of wear resistance.

Ⅱ. What are the precautions for repairing common steel casting defects?

Steel casting is a component made of cast steel. In steel casting, its performance is somewhat similar to that of cast iron, and in use, it is stronger than cast iron.

At the same time, during the casting process of steel casting parts, bubbles and other phenomena are prone to occur. Therefore, what should be paid attention to in the process of repairing steel casting parts?

1. When the welding repair method is to be used to repair the defects of the steel casting parts, the defect situation and the welding repair procedure specification shall be reviewed.

2. When gas cutting or carbon arc gouging is used to remove defects in important castings, necessary preheating should be performed depending on the chemical composition, size and nature of defects of the castings.

3. Defects of steel casting parts may be found during appearance inspection, or after heat treatment or machining. Defects that are not allowed can be removed by machining, chiseling, grinding, gas cutting or carbon arc gouging.

4. After welding repair of casting defects, the repair welding and adjacent base metal must be polished, and non-destructive inspection shall be carried out according to the sketch of the number, size and position of the original defects to confirm that the defects have been completely removed.

5. After the defects are removed from the steel casting parts, non-destructive testing should be carried out to confirm that the defects have been completely removed. For the shallow grooves or pits produced by the removal of defects in the steel casting products, when the strength of the casting is not weakened, it can be ground into a smooth arc-shaped transition surface.