Process to improve magnetic characteristics of carbon steel

Abstract

Abstract The process to improve magnetic characteristics of conventional low-carbon, rimmed steel having the chemical composition, carbon: <0.25 weight percent, silicon: <0.5 weight percent, manganese: <1.65 weight percent, phosphorus: <0.05 weight percent, sulfur: <0.05 weight percent, copper: <0.5 weight percent, and other elements: <0.1 weight percent, comprising: A first stage of raising the temperature of carbon steel above the A3 transformation temperature of approximately 850-910* C. wherein the Alpha -phase gamma -phase transformation takes place in a controlled atmosphere with a dew point of approximately 5* to 50* C., or a water vapor pressure of 6.9-92.5 Torr. A second stage of lowering rapidly the temperature of the carbon steel below 723* C., but not lower than 600* C., maintaining the carbon steel at this temperature for 3 to 10 hours in a weakly oxidizing atmosphere. A third stage of lowering and maintaining said carbon steel at a temperature of 300 to 400* C. for 1 to 2 hours for the purpose of obtaining large ferrite grains in which less than 0.01 weight percent of carbon is present dissolved in the matrix and the residual carbon is present at ferrite grain boundaries, and not in the matrix. A low-carbon, rimmed steel having a ferrite matrix and chemical composition: less than each of the following: 0.25 weight percent carbon, 0.5 weight percent silicon, 1.65 weight percent manganese, 0.05 weight percent phosphorus, 0.05 weight percent sulfur, 0.5 weight percent copper, and 0.1 weight percent other elements, and wherein the ferrite matrix is in the form of grains sufficiently large in particle size to be less than 10 particles per mm.2, said grains having less than 0.01 weight percent of carbon dissolved in the ferrite matrix, and the residual carbon being present at ferrite grain boundaries and not in the ferrite matrix.

Inventors

• 👤 Hideto Hiraoka

Bibliographic Details