Abstract: A ripper shank as the impact and wear resistant component is made of a steel of a specific component composition which has a hardness of HRC 53 or more and HRC 57 or less. The steel includes a matrix including a martensite phase and a residual austenite phase, and first nonmetallic particles dispersed in the matrix and including at least one species selected from the group consisting of MnS, TiCN, and NbCN. The steel does not include a M23C6 carbide.

Abstract: A track link which is a tracked undercarriage component is made of a steel having a specific component composition, and includes a high hardness portion having a hardness of HRC 57 or more and HRC 60 or less, and a low hardness portion. The high hardness portion includes a first matrix including a martensite phase and a residual austenite phase, and first nonmetallic particles dispersed in the first matrix and including at least one species selected from the group consisting of MnS, TiCN, and NbCN, and it does not include a M23C6 carbide. The low hardness portion includes a second matrix including a martensite phase, and second nonmetallic particles dispersed in the second matrix and including at least one species selected from the group consisting of MnS, TiCN, and NbCN, and it does not include a M23C6 carbide.

Abstract: A process for producing a blow molding resin comprises pelletizing a high density polyethylene prepared by means of a highly active Ziegler catalyst, at a temperature of at least 230.degree. C. in the presence of air or oxygen so as not to change the average molecular weight and the molecular weight distribution.

Abstract: A process for producing a blow molding resin comprises pelletizing a high density polyethylene prepared by means of highly active Ziegler catalyst, characterized in that a small amount of a cross linking agent is added to the high density polyethylene and the pelletizing is conducted in an atmosphere containing a small amount of oxygen.