Disclosed is a low-cost non-oriented electrical steel plate with an extremely low aluminum content, which plate comprises the following chemical elements in percentage by mass: 0.003% or less of C, 0.1%-1.2% of Si, 0.1%-0.4% of Mn, 0.01%-0.2% of P, 0.003% or less of S, 0.001% or less of Al, 0.003%-0.01% of O, 0.003% or less of N, and 0.005%-0.05% of Sn, with the condition Si.sup.2/P: 0.89-26.04 being satisfied. In addition, further disclosed is a method for manufacturing the non-oriented electrical steel plate. The method comprises steps of: (1) smelting; (2) continuous casting; (3) hot rolling: wherein a hot rolled plate is subjected to soaking and heat preservation by means of residual heat of hot rolled steel coils, rather than being subjected to normalizing treatment or cover furnace annealing after coiling; (4) primary cold rolling; and (5) continuous annealing. In the non-oriented electrical steel plate of the present invention, reasonable chemical ingredients and process designs are used, and the non-oriented electrical steel plate not only has excellent economy, but also has the properties of high magnetic induction and low iron loss.

A process for making full dense components of a carbon-containing steel, comprises the steps of: a) making a powder of the carbon-containing steel by gas atomization wherein the carbon content is low, less than 0.15 wt %, b) agglomerating the powder from step a) with at least one hydrocolloid and elemental carbon, c) compacting the agglomerated powder from step b) to a density of at least 80% of theoretical density, with the proviso that the compacted agglomerated powder still is porous allowing transport of gas to and from its interior, and d) sintering the compacted powder to a density of more than 98% of theoretical density, preferably more than 99% of theoretical density, wherein a gas comprising carbon is added during sintering and finally subjecting the component to HVC. Advantages include that it is possible to manufacture a dense component of powders which otherwise are difficult to compact.

A process for making full dense components of a carbon-containing steel, comprises the steps of: a) making a powder of the carbon-containing steel by gas atomization wherein the carbon content is low, less than 0.15 wt %, b) agglomerating the powder from step a) with at least one hydrocolloid and elemental carbon, c) compacting the agglomerated powder from step b) to a density of at least 80% of theoretical density, with the proviso that the compacted agglomerated powder still is porous allowing transport of gas to and from its interior, and d) sintering the compacted powder to a density of more than 98% of theoretical density, preferably more than 99% of theoretical density, wherein a gas comprising carbon is added during sintering and finally subjecting the component to HVC. Advantages include that it is possible to manufacture a dense component of powders which otherwise are difficult to compact.

There is provided a surface treatment method in which a processing gas is brought in contact with a heated processing object made of steel, an element in the processing gas is solid-solutionized, and thus a surface treatment is performed on the processing object. The processing object is heated to a heating temperature in a vicinity of a processing temperature at which the surface treatment is performed by heating an atmosphere in which the processing object is disposed. The surface treatment is performed by bringing the processing gas in contact with a surface of the processing object while the processing object which is heated is directly heated to the processing temperature.

A vacuum heat treatment apparatus according to the embodiment comprises a chamber; a thermal insulator in the chamber; a reaction container in the thermal insulator; a heating member between the reaction container and the the thermal insulator for heating the reaction container; and a temperature measuring member in or on a surface of the reaction container, wherein the temperature measuring member comprises a thermocouple and a protective tube surrounding the thermocouple, and the protective tube comprises tungsten (W), tantalum (Ta), or silicon carbide (SiC).

A vacuum heat treatment apparatus according to the embodiment comprises a chamber; a thermal insulator in the chamber; a reaction container in the thermal insulator; a heating member between the reaction container and the the thermal insulator for heating the reaction container; and a temperature measuring member in or on a surface of the reaction container, wherein the temperature measuring member comprises a thermocouple and a protective tube surrounding the thermocouple, and the protective tube comprises tungsten (W), tantalum (Ta), or silicon carbide (SiC).

Method for the preoxidation of high-strength strip steel. The invention relates to an improved method for the preoxidation of high-strength strip steel in a reaction chamber arranged in a furnace chamber. The reaction chamber is sealed at a strip entrance and a strip exit against gas exchange between the furnace chamber and the reaction chamber, and a gas that forms an oxidizing atmosphere in the reaction chamber is introduced, and the gas is continuously circulated within the reaction chamber

A non-oriented electrical steel sheet having high magnetic flux density and a low iron loss at a high frequency is produced by subjecting a slab containing, in mass %, C: not more than 0.0050%, Si: 2.8 to 6.5%, Mn: 0.05 to 2.0%, P: not more than 0.10%, S: not more than 0.0050%, Al: 0.3 to 2.0%, N: not more than 0.0050% and Zn: 0.0005 to 0.0050% to a hot rolling, a hot-band annealing, a cold rolling and a finish annealing, a dew point in the hot-band annealing is set to 0 to 70 ° C. and an atmosphere of the finish annealing has a nitrogen content of not more than 30 vol % and a dew point of not higher than −20° C., and a ratio of the amount of nitrogen present as AlN in an entire sheet thickness to the amount of nitrogen present as AlN in a layer from one-side surface of steel sheet to a depth of 1/20 of sheet thickness is made to not less than 5.0.

A non-oriented electrical steel sheet having high magnetic flux density and a low iron loss at a high frequency is produced by subjecting a slab containing, in mass %, C: not more than 0.0050%, Si: 2.8 to 6.5%, Mn: 0.05 to 2.0%, P: not more than 0.10%, S: not more than 0.0050%, Al: 0.3 to 2.0%, N: not more than 0.0050% and Zn: 0.0005 to 0.0050% to a hot rolling, a hot-band annealing, a cold rolling and a finish annealing, a dew point in the hot-band annealing is set to 0 to 70 ° C. and an atmosphere of the finish annealing has a nitrogen content of not more than 30 vol % and a dew point of not higher than −20° C., and a ratio of the amount of nitrogen present as AlN in an entire sheet thickness to the amount of nitrogen present as AlN in a layer from one-side surface of steel sheet to a depth of 1/20 of sheet thickness is made to not less than 5.0.

A method for making a vehicle body component includes forming a generally flat plate of unhardened, hot-formable sheet steel with a marginal shape which corresponds essentially to the developed configuration of the finished vehicle body component. The formed plate is hot-formed and hardened in a single press tool to define a sheet profile which corresponds to the configuration of the finished vehicle body component, and a surface coating is applied to the sheet profile.