An annealing furnace for annealing a strand of steel. The annealing furnace including a first heating apparatus for heating the strand during operation of the annealing furnace. A transport device advances the strand in a direction of transport through the annealing furnace during operation of the annealing furnace. The annealing furnace also includes a first cooling device for cooling the outer surface of the strand with a gas guide in the direction of transport behind the first heater, wherein the gas guide is arranged in such a manner that a gas flows along the outer surface of the strand during operation of the annealing furnace for cooling the strand.

Disclosed are a high-pressure liquid-state or supercritical-state quenching apparatus, comprising a working chamber, a heating device, a cooling device, a vacuum pump set, a storage tank, a buffer tank, a gas booster, a first pressure gauge, and a temperature controller. According to the Invention, vacuum liquid-state or supercritical-state quenching is implemented, which satisfies a quenching requirement of a large workpiece, and can also achieve an effect of high-pressure gas quenching. In addition, clean heat treatment is implemented, which avoids waste gas and waste water pollution, and is energy-saving and environmentally-friendly heat treatment.

This heat treatment apparatus is configured such that a treating target is conveyed via an intermediate conveyance chamber and accommodated in a heating chamber. The heat treatment apparatus is provided with a gas cooling chamber that is disposed adjacent to the intermediate conveyance chamber and in which the treating target is cooled using a cooling gas containing an oxidizer.

A method for producing a sulfide solid electrolyte powder includes: mixing raw materials to obtain a raw material mixture; synthesizing at least one powder of a sulfide powder and a sulfide precursor powder from the raw material mixture; heat-treating the powder in a heating area to obtain a sulfide solid electrolyte powder; transferring the sulfide solid electrolyte powder to a cooling area; and cooling the sulfide solid electrolyte powder while circulating an inert gas in the cooling area. The heating area and the cooling area are separated.