Tokyo Electron Limited

Nippon Steel Corporation

Tokyo Electron Tohoku Limited

Nippin Steel Corporation

Junichi Kobayashi

Eiichiro Takanabe

Tomohisa Shimazu

Harunori Ushikawa

Seinosuke Yano

Yoshihiro Okamura

Shigeru Ohkita

Tadashi Kasuya

Masao Fuji

Katsuo Kaku

Naoki Saitou

Toshihiko Chiba

In order to conduct welding so that the welded steel shows a decreased residual stress after welding without a post treatment such as a PWHT, the steel for welded structures and the welding wire of the present invention starts a transformation from austenite into martensite at a temperature (Ms temperature) from at least 200&deg; C. to up to 350&deg; C., and has a yield strength from at least 60 kg/mm to up to 120 kg/mm at the transformation starting temperature. The multipass welding process of the present invention comprises forming a weld metal having a Ms temperature of 150&deg; C. to 300&deg; C., and TIG remelt-run welding the surface of the final layer.

Steel for welded structures and welding wire

A heat treatment apparatus comprising a reaction vessel located in a vertical furnace, and a ladder boat for mounting a plurality of semiconductor wafers one above another in parallel with each other. A vertical mounting pitch of mounting the wafers on the ladder boat is set at, e.g., 40 mm. When a treatment temperature is 1000.degree. C., intra-surface temperature differences of the wafers, objects to be treated, can be suppressed to 10.degree. C. at the time of passing 900.degree. C. even when 600.degree. C. is raised to 100.degree. C. at a 100.degree. C./min rate, whereby no slip occurs in large-diameter semiconductor wafers of an above 250 mm diameter even with high temperature increases at high rates in heat treatments, as of oxidation, diffusion, etc.

Heat treatment process for preventing slips in semiconductor wafers

A number of semiconductor wafers are held in a ladder boat at, e.g., a 3/16 inch arrangement pitch of wafers W, and the ladder boat is loaded into a vertical heat treatment furnace. Then an interior of the heat treatment furnace is heated up to 900.degree. C. at a high temperature raising rate of, e.g., 30.degree. C./minute. Subsequently the interior is heated in steps at low temperature raising rates, e.g., at below 14.degree. C./minute up to a temperature region of, e.g., 980.degree. C. and at below 5.degree. C./minute up to a heating temperature of 1100.degree. C. These temperature raising rates are determined, based on results given by observation of presence and absence of slips in the wafers W heat-treated in various temperature raising patterns for different wafer arrangement pitches, so that the wafers can be heat-treated effectively without occurrence of slips. Widening said arrangement pitch to 3/8 inches allows higher temperature raising rates to be set.

Heat treatment process

A process for producing a high toughness, high strength steel having excellent resistance to stress corrosion cracking including the steps of: preparing a steel slab including 0.02 to 0.10 wt % of C, 0.50 wt % or less Si, 0.4 to 1.5 wt % Mn, 1.0 to 7.5 wt % Ni, more than 1.0 wt % up to 1.5 wt % Mo, 0.80 wt % or less Cr, 0.01 to 0.08 wt % sol. Al, and the balance of Fe and unavoidable impurities; heating the steel slab to a temperature of from 1000.degree. C. to 1250.degree. C.; hot rolling the heated steel slab at a finishing nip temperature of from 700.degree. C. to 880.degree. C., at a total reduction rate of 40% or more effected at the finishing nip temperature or lower, and at a finishing temperature of 650.degree. C. or higher, to provide a steel plate; then quenching the steel plate by initiating water cooling at a temperature of the A.sub.r3 point thereof or higher and by terminating the water cooling at a temperature of 150.degree. C. or lower; and tempering the quenched steel plate at a temperature of the A.sub.c1 point thereof or lower.

Process for producing high toughness, high strength steel having

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Sagamihara, Japan

Junichi Kobayashi