GAS SOFT NITRIDING PROCESS OF LOW-ALLOY STEEL

• Main Authors: UMEHARA TAKAHIDE, OFUJI YOSHIHIRO
• Format: Patent
• Language: English; Japanese
• Published: 05.10.2015
• Subjects: CHEMICAL SURFACE TREATMENT; CHEMISTRY; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATIONOR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY IONIMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING MATERIAL WITH METALLIC MATERIAL; COATING METALLIC MATERIAL; DIFFUSION TREATMENT OF METALLIC MATERIAL; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL; MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS; METALLURGY; METALLURGY OF IRON; MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THESURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION

PROBLEM TO BE SOLVED: To provide a gas soft nitriding process of a low-alloy steel, capable of securing a constant depth of a cured layer and suppressing the generation of a compound layer with low toughness.SOLUTION: The gas soft nitriding process of a low-alloy steel for performing gas soft nitriding process by heating the low-alloy steel to 550-620°C for a processing time A of 1.5-10 hours, comprises: performing high Kn value process with a nitriding potential Knof 0.10-1.00, an average value Knof 0.20-0.55 and a processing time of X hours; then performing low Kn value process with a nitriding potential Knof 0.01-0.20, an average value Knof 0.02-0.15, and a processing time of Y hours; and acquiring an average value Knof nitriding potential of soft nitriding process of 0.05-0.20 on the basis of the average value Kn, the average value Kn, the processing time A, and the processing times X and Y of the high Kn value and low Kn value processes. 【課題】一定の硬化層深さを確保し、低靭性である化合物層の生成を抑制し得る、低合金鋼のガス軟窒化方法を提供する。【解決手段】低合金鋼を５５０〜６２０℃に加熱し、処理時間Ａを１．５〜１０時間とするガス軟窒化処理を行うに際し、窒化ポテンシャルＫｎXが０．１０〜１．００、平均値ＫｎXaveが０．２０〜０．５５であり、処理時間をＸ時間とする高Ｋｎ値処理の後、窒化ポテンシャルＫｎYが０．０１〜０．２０の範囲内であり、平均値ＫｎYaveが０．０２〜０．１５であり、処理時間をＹ時間とする低Ｋｎ値処理を行い、前記平均値ＫｎXaveと、前記平均値ＫｎYaveと、前記処理時間Ａと、前記高Ｋｎ値処理及び前記低Ｋｎ値処理の処理時間Ｘ及びＹとから、軟窒化処理の窒化ポテンシャルの平均値Ｋｎaveが０．０５〜０．２０であることを特徴とする低合金鋼のガス軟窒化処理方法。【選択図】図２