Abstract: The present invention provides hot rolled steel plates and sheets having a tensile strength of 34 to 62 kgf/mm.sup.2 and excellent in a uniform elongation even after cold working the steel plates and sheets to give round and square tubes, shapes, sheet piles, etc., to such an ordinary degree that the productivity is not lowered, and a process for producing the hot rolled steel plates and sheets. The hot rolled steel plates and sheets contain from 0.04 to 0.25% of C, from 0.0050 to 0.0150% of N and from 0.003 to 0.050% of Ti, also contain from 0.0008 to 0.015% of TiN having a particle size exceeding 1 .mu.m and dispersed in the matrix thereof, and have Ceq. (WES) of 0.10 to 0.45%. The process comprises heating a steel slab containing the constituents as mentioned above to 1,000 to 1,300.degree. C., starting to roll the steel slab subsequently and finishing rolling at a temperature of at least the Ar.sub.3 transformation point, and air cooling from a temperature of at least 500.degree. C.

Abstract: In a scroll compressor having a stationary scroll and a revolving scroll, and a refrigerator incorporating this scroll compressor, the stationary scroll has a gas suction hole formed in its radially outer portion, a gas discharge hole formed in its central portion, and gas injection holes and a liquid injection hole formed between the suction and discharge holes. The gas injection holes are formed in a radially outer portion of the stationary scroll, and the liquid injection hole are formed in a central portion of the stationary scroll. The refrigerator incorporates the scroll compressor, a condenser, decompressors and an evaporator to form a refrigerating circuit. The liquid injection hole of the scroll compressor is directly connected by piping to the outlet of the condenser, and the gas injection holes are connected by piping to the outlet of the condenser through one of the decompressors.

Abstract: A screw compressor in which a pair of screw rotors supported by bearings and accommodated in a casing act to compress a gas and in which a slide valve disposed between an inner wall of the casing and the pair of screw rotors is capable of moving axially while maintaining a small gap between itself and the outer peripheries of the screw rotors, the rate of gas flow bypassed to an inlet port during compression being regulated by axially moving the slide valve.

Abstract: A refrigerant gas injection system for a refrigeration cycle of the type having a screw compressor provided with a slide valve for controlling the compression capacity of the screw compressor, an economizer disposed in a passage for refrigerant liquid and adapted for subcooling the refrigerant liquid by the refrigerant of a reduced pressure, and a refrigerant gas injection line through which the refrigerant gas generated in the economizer is injected into the compression chamber of the screw compressor in its compression phase. The refrigerant gas injection system has a gas injection controller adapted to enable the injection of the refrigerant gas when the screw compressor is operating at full (100%) capacity or load level and to prevent the injection of the refrigerant gas when the screw compressor is operating in unloaded state.