Abstract: In order to prevent a mistrip caused by a closing operation of a toggle link mechanism, a trip lever is not mounted on a fixed frame of an opening/closing mechanism, but is mounted on a yoke of a disengaging device serving as a support base for the trip lever. The opening/closing mechanism and the disengaging device are held in a common casing. As a result, an impact force, produced at the time of closing the contact between two contacts by the toggle link mechanism, is transmitted through the casing, so that such a mistrip can be prevented.

Abstract: A high tensile strength steel sheet excellent in processibility which can satisfy a strength, a total elongation, and stretch-flanging property (hole enlarging rate) at a further high level and comprises a matrix microstructure of tempered martensite or tempered bainite and, if necessary, ferrite, and a second phase of retained austenite, wherein (1) the steel comprising C: 0.10 to 0.6 mass %, Si: 1.0 mass % or smaller, Mu: 1.0 to 3 mass %, Al: 0.3 to 2.0 mass %, P: 0.02 mass % or smaller, S: 0.

Abstract: In order to prevent a mistrip caused by a closing operation by a toggle mechanism, a trip lever 23 is not mounted on a fixed frame of a mechanism portion 8, but is mounted on a yoke 30 of a disengaging device 9 serving as a support base for this trip lever. The mechanism portion 8 and the disengaging device 9 are held on a common casing 10, and therefore an impact force, produced at the time of closing the contact between two contacts 2 and 3 by the toggle mechanism, is not completely prevented from being transmitted to the trip lever 23, while this impact force is transmitted through the casing 10, and therefore is far smaller as compared with the case where the trip lever 23 is supported on the fixed frame 13, so that such a mistrip can be prevented.

Abstract: A high strength steel sheet having (2-1) a base phase structure, the base phase structure being tempered martensite or tempered bainite and accounting for 50% or more in terms of a space factor relative to the whole structure, or the base phase structure comprising tempered martensite or tempered bainite which accounts for 15% or more in terms of a space factor relative to the whole structure and further comprising ferrite, the tempered martensite or the tempered bainite having a hardness which satisfies the relation of Vickers hardness (Hv)≧500[C]+30[Si]+3[Mn]+50 where [ ] represents the content (mass %) of each element, and (2-2) a second phase structure comprising retained austenite which accounts for 3 to 30% in terms of a space factor relative to the whole structure and optionally further comprising bainite and/or martensite, the retained austenite having a C concentration (C&ggr;R) of 0.8% or more.

Abstract: In order to prevent a mistrip caused by a closing operation of a toggle link mechanism, a trip lever is not mounted on a fixed frame of an opening/closing mechanism, but is mounted on a yoke of a disengaging device serving as a support base for the trip lever. The opening/closing mechanism and the disengaging device are held in a common casing. As a result, an impact force, produced at the time of closing the contact between two contacts by the toggle link mechanism, is transmitted through the casing, so that such a mistrip can be prevented.

Abstract: Disclosed is a dual-phase steel sheet having low yield ratio, excellent in the balance for strength-elongation and for strength-stretch flange formability, and also excellent in bake hardening property containing (on the mass% basis).

Abstract: A high-strength hot-rolled steel sheet superior in stretch flange formability which comprises C (0.01-0.10 mass %), Si (no more than 1.0 mass %), Mn (no more than 2.5 mass %), P (no more than 0.08 mass %), S (no more than 0.005 mass %), Al (0.015-0.050 mass %), and Ti (0.10-0.30 mass %), with the remainder being substantially Fe, said hot-rolled steel sheet having a structure composed mainly of ferrite in which the unit grain is surrounded by grains such that adjacent grains differ in orientation more than 15°, the unit grain having an average particle diameter (d) no larger than 5 &mgr;m. This steel sheet is produced by the steps of heating, rolling, cooling, and coiling under the following conditions. Heating temperature: 1150-1300° C.; reduction in rolling at 900-840° C.: no less than 70%; cooling rate: no less than 60° C./s; and coiling temperature: 300-500° C. or 600-750° C.

Abstract: Disclosed herein is a high-strength hot-rolled steel sheet superior in stretch-flanging properties and fatigue properties which comprises (in mass %) 0.01-0.10% C, less than 2% Si (including 0%), 0.5-2% Mn, less than 0.08% P (including 0%), less than 0.01% S (including 0%), less than 0.01% N (including 0%), 0.01-0.1% Al, and at least one of 0.1-0.5% Ti and less than 0.8% Nb (including 0%), with the granular bainitic structure accounting for more than 80% (by area) in its sectional metallographic structure. Disclosed also herein is a process for producing said steel sheet.

Abstract: Disclosed herein is a high-strength hot-rolled steel sheet superior in stretch-flanging properties and fatigue properties which comprises (in mass %) 0.01-0.10% C, less than 2% Si (including 0%), 0.5-2% Mn, less than 0.08% P (including 0%), less than 0.01% S (including 0%), less than 0.01% N (including 0%), 0.01-0.1% Al, and at least one of 0.1-0.5% Ti and less than 0.8% Nb (including 0%), with the granular bainitic structure accounting for more than 80% (by area) in its sectional metallographic structure. Disclosed also herein is a process for producing said steel sheet.

Abstract: In order to prevent a mistrip caused by a closing operation by a toggle mechanism, a trip lever 23 is not mounted on a fixed frame of a mechanism portion 8, but is mounted on a yoke 30 of a disengaging device 9 serving as a support base for this trip lever. The mechanism portion 8 and the disengaging device 9 are held on a common casing 10, and therefore an impact force, produced at the time of closing the contact between two contacts 2 and 3 by the toggle mechanism, is not completely prevented from being transmitted to the trip lever 23, while this impact force is transmitted through the casing 10, and therefore is far smaller as compared with the case where the trip lever 23 is supported on the fixed frame 13, so that such a mistrip can be prevented.

Abstract: A high-strength hot-rolled steel sheet superior in stretch flange formability which comprises C (0.01-0.10 mass %), Si (no more than 1.0 mass %), Mn (no more than 2.5 mass %), P (no more than 0.08 mass %), S (no more than 0.005 mass %), Al (0.015-0.050 mass %), and Ti (0.10-0.30 mass %), with the remainder being substantially Fe, said hot-rolled steel sheet having a structure composed mainly of ferrite in which the unit grain is surrounded by grains such that adjacent grains differ in orientation more than 15°, said unit grain having an average particle diameter (d) no larger than 5 &mgr;m. This steel sheet is produced by the steps of heating, rolling, cooling, and coiling under the following conditions. Heating temperature: 1150-1300° C.; reduction in rolling at 900-840° C.: no less than 70%; cooling rate: no less than 60° C./s; and coiling temperature: 300-500° C. or 600-750° C.

Abstract: A P- and Ti-added galvannealed steel sheet superior in ductility, and a process for production thereof. It is made of a cold-rolled steel sheet and has alloyed hot-dip galvanizing on the surface thereof, said cold-rolled steel sheet having the chemical composition (in terms of wt %) of C: less than 0.010%, Si: no more than 0.5%, Mn: 1.0˜3.0%, P: no more than 0.20%, S: no more than 0.01%, Al: 0.005˜0.10%, N: no more than 0.0050%, Ti/48−(C/12+N/14+S/32): 0.0003˜0.0018 with the remainder being chiefly Fe, and said cold-rolled steel sheet being characterized by &rgr;1≦107 and &rgr;2≦5×105, where &rgr;1 is the number of precipitates whose particle diameter (D) is in the range of 10 nm≦D<100 nm and &rgr;2 is the number of precipitates whose particle diameter (D) is in the range of 100 nm≦D.

Abstract: A hot-dip galvanized steel sheet which is produced from a cold-rolled steel sheet, as a base steel sheet, consisting essentially of C: 0.010-0.06 wt %, Si: no more than 0.5 wt %, Mn: no less than 0.5 wt % and less than 2.0 wt %, P: no more than 0.20 wt %, S: no more than 0.01 wt %, Al: 0.005-0.10 wt %, N: no more than 0.005 wt %, Cr: no more than 1.0 wt %, Mn+1.3Cr: 1.9-2.3 wt %, Fe: remainder, and having a structure composed of ferrite and a second phase containing martensite, said second phase in the structure accounting for no more than 20% in terms of area and martensite in the second phase accounting for no less than 50%, and which has a zinc-plated layer formed on the surface thereof by hot-dip galvanizing or hot-dip galvannealing. A process for production of said hot-dip galvanized steel sheet. This steel sheet has a composite structure containing martensite and yet it has a low strength (no higher than 500 MPa) and also has good strength-ductility balance.