Apparatus is provided for metallurgical heat treatment of coil springs, or similarly shaped workpieces and articles of manufacture, by electric resistance heating along the entire length of the workpiece so that the ends of the workpiece can be heat treated to the same degree and quality as the section of the workpiece between its two ends.

Apparatus is provided for metallurgical heat treatment of coil springs, or similarly shaped workpieces and articles of manufacture, by electric resistance heating along the entire length of the workpiece so that the ends of the workpiece can be heat treated to the same degree and quality as the section of the workpiece between its two ends.

A method to manufacture a steel wire spring core for a mattress or for seating is described, which comprises the steps of providing a carrier comprising steel wire; repeatedly cold coiling a steel wire spring from steel wire taken from the carrier; and connecting a series of the coiled steel wire springs to each other. The steel wire has a diameter d between 0.8 and 4.5 mm; and has a drawn pearlitic microstructure. The steel wire comprises a steel alloy having a carbon content between 0.35 wt % and 0.85 wt %. The steel wire on the carrier has a ratio—expressed as a percentage—of the yield strength R.sub.po 2 (in MPa) over the tensile strength R.sub.m (in MPa) higher than 85%.

A method to manufacture a steel wire spring core for a mattress or for seating is described, which comprises the steps of providing a carrier comprising steel wire; repeatedly cold coiling a steel wire spring from steel wire taken from the carrier; and connecting a series of the coiled steel wire springs to each other. The steel wire has a diameter d between 0.8 and 4.5 mm; and has a drawn pearlitic microstructure. The steel wire comprises a steel alloy having a carbon content between 0.35 wt % and 0.85 wt %. The steel wire on the carrier has a ratio—expressed as a percentage—of the yield strength R.sub.po 2 (in MPa) over the tensile strength R.sub.m (in MPa) higher than 85%.

Provided is a titanium copper foil which has required high strength when used as a spring, has an improved etching property, and has decreased settling, and which can be suitably used as a conductive spring material for use in electronic device parts such as autofocus camera modules. The titanium copper foil according to the present invention contains from 1.5 to 5.0% by mass of Ti, the balance being Cu and inevitable impurities, wherein in a Ti concentration curve obtained by analyzing a cross section parallel to a rolling direction along a thickness direction by STEM-EDX, a lower concentration Ti layer having a Ti concentration less than an average value of Ti concentrations in the Ti concentration curve and a higher concentration Ti layer having a Ti concentration equal to or higher than the average value of the Ti concentrations in the Ti concentration curve are alternately present in a thickness direction, and wherein the titanium copper foil satisfies 1.0% by mass≤H.sub.H≤30% by mass, and H.sub.H/H.sub.L≥1.1, in which H.sub.H and H.sub.L are as defined in the present specification.

Provided is a titanium copper foil which has required high strength when used as a spring, has an improved etching property, and has decreased settling, and which can be suitably used as a conductive spring material for use in electronic device parts such as autofocus camera modules. The titanium copper foil according to the present invention contains from 1.5 to 5.0% by mass of Ti, the balance being Cu and inevitable impurities, wherein in a Ti concentration curve obtained by analyzing a cross section parallel to a rolling direction along a thickness direction by STEM-EDX, a lower concentration Ti layer having a Ti concentration less than an average value of Ti concentrations in the Ti concentration curve and a higher concentration Ti layer having a Ti concentration equal to or higher than the average value of the Ti concentrations in the Ti concentration curve are alternately present in a thickness direction, and wherein the titanium copper foil satisfies 1.0% by mass≤H.sub.H≤30% by mass, and H.sub.H/H.sub.L≥1.1, in which H.sub.H and H.sub.L are as defined in the present specification.

A method for manufacturing a hollow spring member having a hollow steel spring rod having terminal sealed portions at both ends thereof. Each terminal sealed portion has a rotationally symmetric shape in which an axis passing through a center of the spring rod is an axis of symmetry. Each terminal sealed portion has an end wall portion including an end face; an arc-shaped smoothly curved surface between an outer peripheral surface of the spring rod and the end face, and a hermetically closed distal-end-center closure portion on the axis passing through the center of the spring rod. The method includes forming each of the end portions of the spring rod by forming a chamfered portion on an inner or outer peripheral side of the end portion of a hollow wire, the end portion having an opening portion at a distal end, heating the end portion of the hollow wire having the chamfered portion, and spinning the heated end portion to be gathered toward the axis from the outer peripheral side by a jig. The end wall portion, which includes the distal-end-center closure portion, is formed by the distal end of the end portion being joined together on the axis.

Provided is a titanium copper foil which has required high strength when used as a spring, has an improved etching property, and has decreased settling, and which can be suitably used as a conductive spring material for use in electronic device parts such as autofocus camera modules. The titanium copper foil according to the present invention contains from 1.5 to 5.0% by mass of Ti, the balance being Cu and inevitable impurities, wherein in a Ti concentration curve obtained by analyzing a cross section parallel to a rolling direction along a thickness direction by STEM-EDX, a lower concentration Ti layer having a Ti concentration less than an average value of Ti concentrations in the Ti concentration curve and a higher concentration Ti layer having a Ti concentration equal to or higher than the average value of the Ti concentrations in the Ti concentration curve are alternately present in a thickness direction, and wherein the titanium copper foil satisfies 1.0% by mass≤H.sub.H≤30% by mass, and H.sub.H/H.sub.L≥1.1, in which H.sub.H and H.sub.L are as defined in the present specification.

Provided is a titanium copper foil which has required high strength when used as a spring, has an improved etching property, and has decreased settling, and which can be suitably used as a conductive spring material for use in electronic device parts such as autofocus camera modules. The titanium copper foil according to the present invention contains from 1.5 to 5.0% by mass of Ti, the balance being Cu and inevitable impurities, wherein in a Ti concentration curve obtained by analyzing a cross section parallel to a rolling direction along a thickness direction by STEM-EDX, a lower concentration Ti layer having a Ti concentration less than an average value of Ti concentrations in the Ti concentration curve and a higher concentration Ti layer having a Ti concentration equal to or higher than the average value of the Ti concentrations in the Ti concentration curve are alternately present in a thickness direction, and wherein the titanium copper foil satisfies 1.0% by mass≤H.sub.H≤30% by mass, and H.sub.H/H.sub.L≥1.1, in which H.sub.H and H.sub.L are as defined in the present specification.

The invention relates to a steel wire suitable for making a spring or medical wire products which remarkably improve the performance of conventional stainless steel wire. The steel comprises (in wt. %): C: 0.02 to 0.15, Si: 0.1 to 0.9, Mn: 0.8 to 1.6, Cr 16 to 20, Ni: 7.5 to 10.5, Mo: ≤3, Al: 0.5 to 2.5, Ti: ≤0.15, N: ≤0.05, optional elements, and impurities, balance Fe, wherein the total amount of Cr and Ni is 25 to 27 wt. %, and wherein the steel has a microstructure including, in volume % (vol. %), martensite: 40 to 90, austenite: 10 to 60, and delta ferrite: ≤5.