Sand sticking casting defects of cast steel bucket teeth

The bucket teeth on the excavator are the combination of the tooth tip and the tooth seat (see Fig. 1 and Fig. 2). The bucket teeth of the excavator are connected by the pin shaft. If the worn and failed part of the bucket teeth is the tooth tip, just replace the tooth tip. Bucket teeth are the most common vulnerable and consumable parts used in excavators. Due to its direct impact with various rocks and coal seams, the operating conditions are very bad and it is very easy to wear and fracture. Therefore, bucket teeth must have high impact toughness and good wear resistance, as well as high matrix strength and toughness. The impact toughness value of bucket teeth material is AK ≥ 5.0j/cm2; The basic hardness of bucket teeth (after water toughening treatment) is 180 ~ 229hbw, and has strong work hardening ability; Columnar crystals are not allowed in the casting structure, and the grain size grade must be ≥ 5; Repair welding, slag inclusion, inclusion, crack and other casting defects are not allowed for castings.

Cast steel bucket tooth tip of excavator
Cast steel bucket tooth seat of excavator

(1) Practice has proved that fine sand can be used in wet molding to prevent sand sticking of steel castings; In order to ensure the air permeability, coarse-grained sand should be used. The surface of the sand mold should be coated with anti sticking sand coating, which can cover the gap of the mold. In order to reduce the gap of the mold, the mold needs to ensure sufficient compactness; And drying or surface drying.

(2) For steel castings, the thickness of oxide layer between metal and mold can be increased to promote the formation of oxide layer and peel off sand layer. Adding a small amount of iron oxide powder to the surface sand can also significantly prevent sand sticking. Because the iron oxide powder promotes the sintering of the sand mold surface, the compact sintered shell formed is easy to peel off from the casting during cleaning.

(3) Low alloy wear-resistant cast steel is used to produce excavator bucket teeth. For sand sticking casting defects, the method of replacing molding sand (because it was intended to replace silicon sand with zirconium sand) has not been adopted so far. The enterprise is based on the consideration of production cost. As long as the quality of each process is well controlled, a more ideal effect can also be obtained.