Abstract: The present invention provides a spring steel showing a sufficient reduction in area and an impact toughness while the steel has a high strength, in particular a tensile strength as high as at least 1,500 Mpa. A high toughness spring steel according to the present invention comprises, based on mass, 0.45 to 0.85% of C, 0.9 to 2.5% of Si, 0.1 to 1.2% of Mn, 0.1 to 2.0% of Cr, 0.005 to 0.07% of Ti, 0.001 to 0.007% of N, the Ti content being greater than four times the N content in terms of percent by mass, 0.0005 to 0.0060% B, at least one of 0.0005 to 0.01% Mg, 0.0005 to 0.01% La, and 0.0005 to 0.01% Ce, P and S with restrictive contents of less than 0.020% and less than 0.020%, respectively, and the balance of Fe and unavoidable impurities, and selectively contains V, Nb, Ni, Mo and Cu. The percent area of oxides and sulfides is not more than 0.1%.

Abstract: This invention provides an oil-tempered wire having high strength (tensile strength of not less than 1960 MPa) and excellent workability and specifically provides a steel wire for high-strength springs comprising as steel components, in weight percent, C   0.4-0.7% Si   1.2-2.5% Mn   0.1-0.5% Cr   0.4-2.0% Al 0.0001-0.005%, and being limited to P not more than 0.015% and S not more than 0.015%, the balance being Fe and unavoidable impurities, the steel wire having no nonmetallic inclusions of a size greater than 15 &mgr;m, a tensile strength of not less than 1960 MPa, and a yield ratio (&sgr;0.2/&sgr;B) of not less than 0.8 and not greater than 0.9 or a yield ratio (&sgr;0.2/&sgr;B) of not less than 0.8 and an amount of residual austenite of not greater than 6%. This invention also provides a method of producing the steel wire.

Abstract: The present invention provides, at low cost, a valve spring steel having a tensile strength as high as 210 to 240 kgf/mm.sup.2 after oil tempering. The high strength spring steel comprises, based on weight, 0.65 to 0.85% of C, 1.90 to 2.40% of Si, 0.50 to 1.00% of Mn, 0.70 to 1.30% of Cr, 0.10 to 0.30% of Mo, 0.20 to 0.50% of V, 0.01 to 0.04% of Nb and the balance Fe and unavoidable impurities and is subjected to heating at temperature of 1,050 to 1,250.degree. C. and then to rolling so that carbides in the steel have a size of up to 0.15 .mu.m in terms of equivalent circle. A valve spring having a tensile strength as high as 210 to 240 kgf/mm.sup.2 after oil tempering and stabilized quality can be produced while the material cost is greatly reduced by decreasing costly alloying components as much as possible.

Abstract: In an incoming call service by which an extension can be directly called when a call comes in from another office, a dedicated terminal for selecting an extension to which the incoming call is connected is installed to enable the user to select it as desired, thereby increasing usage of call incoming lines for effective use. An exchange which connects an incoming call from another office directly to an extension, an input device for accepting specification of an extension corresponding to a specific incoming call, and a controller which includes a definition device for defining the correspondence between the specific incoming call and extension are provided. Upon receipt of an incoming call, the exchange connects the call to its corresponding extension in response to the correspondence defined in the definition device.

Abstract: In an incoming call service by which an extension can be directly called when a call comes in from another office, a dedicated terminal for selecting an extension to which the incoming call is connected is installed to enable the user to select it as desired, thereby increasing usage of call incoming lines for effective use. An exchange which connects an incoming call from another office directly to an extension, an input device for accepting specification of an extension corresponding to a specific incoming call, and a controller which includes a definition device for defining the correspondence between the specific incoming call and extension are provided. Upon receipt of an incoming call, the exchange connects the call to its corresponding extension in response to the correspondence defined in the definition device.

Abstract: In an incoming call service by which an extension can be directly called when a call comes in from another office, a dedicated terminal for selecting an extension to which the incoming call is connected is installed to enable the user to select it as desired, thereby increasing usage of call incoming lines for effective use. An exchange which connects an incoming call from another office directly to an extension, an input device for accepting specification of an extension corresponding to a specific incoming call, and a controller which includes a definition device for defining the correspondence between the specific incoming call and extension are provided. Upon receipt of an incoming call, the exchange connects the call to its corresponding extension in response to the correspondence defined in the definition device.

Abstract: A cemented carbide tool of excellent wear resistance and fracture resistance includes a substrate of cemented carbide, and a ceramic coating layer by chemical vapor deposition. The thickness of the layer is in the range of between 2 .mu.m to 20 .mu.m, and the layer has cracks of such a depth that the cracks extend perpendicularly from a surface of the layer to the substrate. The cracks are formed in a network-like pattern to minutely divide the layer. The average value of the depths of the cracks in a direction perpendicular to the surface of the layer is not less than the thickness of the layer and not more than a value equal to the coating thickness plus 5 .mu.m. The average value of widths of the cracks is not more than 2 .mu.m. The average value of intervals between the cracks is not less than 10 .mu.m and not more than 100 .mu.m.