Abstract: Helical compression spring for use in an actuator for opening and closing a door or a tailgate of a car has an outer diameter between 15 and 50 mm and comprises a helically coiled steel wire. The steel wire has a non-circular cross-section with an equivalent diameter d (in mm) of the steel wire is between 1 mm and 12 mm. The cross-section may have at least two opposing parallel sides. The cross-section further has rounded edges, wherein the rounded edges have a radius of curvature ranging from 0.10 mm to 5.0 mm. The microstructure of the steel wire in the helical compression spring is cold deformed pearlite. In comparison with helical compression springs with round cross-sections, the non-round helical compression springs may occupy less space or reach higher breaking loads within the same space.

Abstract: A helical compression spring has an outer diameter between 15 and 50 mm. The helical compression spring having a helically coiled steel wire. The diameter d of the steel wire is between 2 and 5 mm. The steel wire contains a steel alloy having between 0.8 and 0.95 wt % C; between 0.2 and 0.9 wt % Mn; between 0.1 and 1.4 wt % Si; between 0.15 and 0.4 wt % Cr; optionally between 0.04 and 0.2 wt % V; optionally between 0.0005 and 0.008 wt % B; optionally between 0.02 and 0.06 wt % Al; unavoidable impurities; and the balance being iron. The steel alloy has a carbon equivalent higher than 1. The carbon equivalent is defined as: C wt %+(Mn wt %/6)+(Si wt %/5)+(Cr wt %/5)+(V wt %/5). The microstructure of the steel wire in the helical compression spring is drawn lamellar pearlite.

Abstract: An actuator for opening and closing a door or a tailgate of a car contains a helical compression spring and a motor. The helical compression spring is provided for opening a door or the tailgate of a car when compressive forces of the helical compression spring are released. The motor is provided for compressing the helical compression spring in order to close the door or the tailgate of the car. The helical compression spring contains a helically coiled coated steel wire. The helically coiled coated steel wire contains a steel core and a metallic coating layer. The steel core contains a steel alloy. The steel alloy contains 0.8 to 0.95 wt % carbon, 0.2 to 0.9 wt % manganese; 0.1 to 1.4 wt % silicon; optionally one or more micro-alloying element. The microstructure of the steel core is drawn lamellar pearlite. The metallic coating layer contains at least 84% by mass of zinc.