A grease composition which contains a base oil (A), a urea-based thickener (B), a sarcosine derivative (C), and a fatty acid zinc salt (D), wherein particles containing the urea-based thickener (B) in the grease composition satisfies Requirement (I). The base oil (A) is a blended base oil containing a high viscosity hydrocarbon-based synthetic oil having a specific kinematic viscosity (A1). A low viscosity hydrocarbon-based synthetic oil having a specific kinematic viscosity (A2). An ultra-high viscosity hydrocarbon-based synthetic oil has a number average molecular weight (Mn) of 2,500 to 4,500 and a specific kinematic viscosity (A3). A 40° C. kinematic viscosity of the base oil (A) is 500 mm.sup.2/s to 1,500 mm.sup.2/s. A viscosity index of the base oil (A) is 140 or more. A content of the fatty acid zinc salt (D) is 10 mass % to 20 mass % based on a total amount of the grease composition.

A mixed powder for powder metallurgy comprises: an iron-based powder; and a lubricant, wherein the lubricant consists of a low-melting-point lubricant having a melting point of 86° C. or less and a high-melting-point lubricant having a melting point of more than 86° C., the low-melting-point lubricant has at least one of an amide group, an ester group, an amino group, and a carboxyl group, a ratio R1 of the low-melting-point lubricant to whole of the lubricant is 5 mass % or more and less than 90 mass %, a ratio R2 of a mass of a free lubricant to a mass of a binding lubricant is 0 or more and 15 or less, and an amount R3 of the low-melting-point lubricant contained as the free lubricant is less than 0.10 parts by mass with respect to 100 parts by mass of the iron-based powder.

A mixed powder for powder metallurgy comprises: an iron-based powder; and a lubricant, wherein the lubricant consists of a low-melting-point lubricant having a melting point of 86° C. or less and a high-melting-point lubricant having a melting point of more than 86° C., the low-melting-point lubricant has at least one of an amide group, an ester group, an amino group, and a carboxyl group, a ratio R1 of the low-melting-point lubricant to whole of the lubricant is 5 mass % or more and less than 90 mass %, a ratio R2 of a mass of a free lubricant to a mass of a binding lubricant is 0 or more and 15 or less, and an amount R3 of the low-melting-point lubricant contained as the free lubricant is less than 0.10 parts by mass with respect to 100 parts by mass of the iron-based powder.

A lubricant composition according to the present invention contains a fatty acid metal salt, a metal dithiocarbamate, and an additive having an effect of increasing an acid value of the lubricant composition, whereby fretting resistance performances are further improved.

A lubricant composition according to the present invention contains a fatty acid metal salt, a metal dithiocarbamate, and an additive having an effect of increasing an acid value of the lubricant composition, whereby fretting resistance performances are further improved.

This ball screw grease composition for a rack-assisted electric power steering contains a thickener, a base oil, and at least one compound selected from the group consisting of a Ca sulfonates, fatty acids, and triglycerides, wherein the kinematic viscosity of the base oil at 40° C. is 4-100 mm2/s, and the worked penetration of the composition is 265-385.

This ball screw grease composition for a rack-assisted electric power steering contains a thickener, a base oil, and at least one compound selected from the group consisting of a Ca sulfonates, fatty acids, and triglycerides, wherein the kinematic viscosity of the base oil at 40° C. is 4-100 mm2/s, and the worked penetration of the composition is 265-385.

The invention provides a grease composition for lubricating resins which contains a base oil, a diurea compound represented by formula (I) as a thickener: R.sup.1—NHCONH —R.sup.2—NHCONH—R.sup.3 (I) (wherein R.sup.2 represents a bivalent aromatic hydrocarbon group having 6 to 15 carbon atoms, and R.sup.1 and R.sup.3 each independently represent a straight-chain or branched alkyl group having 8 to 22 carbon atoms), and a chained hydrocarbon polymer having a weight-average molecular weight of 20,000 to 300,000.

The invention provides a grease composition for lubricating resins which contains a base oil, a diurea compound represented by formula (I) as a thickener: R.sup.1—NHCONH —R.sup.2—NHCONH—R.sup.3 (I) (wherein R.sup.2 represents a bivalent aromatic hydrocarbon group having 6 to 15 carbon atoms, and R.sup.1 and R.sup.3 each independently represent a straight-chain or branched alkyl group having 8 to 22 carbon atoms), and a chained hydrocarbon polymer having a weight-average molecular weight of 20,000 to 300,000.

Provided is a lubricant for a gas insulated switchgear, with which properties of a base oil such as heat resistance, evaporation loss, fluidity under a low temperature, and chemical stability (oxidation resistance and HF resistance) are balanced at a level higher than the conventional level, and long service life and high reliability of the gas insulated switchgear are achieved. A lubricant for a gas insulated switchgear according to the present invention, contains: a base oil containing a polyalphaolefin having a kinematic viscosity at 40° C. of 50 mm.sup.2/s or more; and a thickener containing bisamides.