HIGH STRENGTH HOT-DIP GALVANIZED STEEL SHEET AND METHOD OF PRODUCING HIGH STRENGTH HOT-DIP GALVANIZED STEEL SHEET

• Main Authors: OTOMO RYOSUKE, TAKEDA MIKAKO
• Format: Patent
• Language: English; Japanese
• Published: 20.04.2017
• Subjects: ALLOYS; 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; FERROUS OR NON-FERROUS ALLOYS; 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; TREATMENT OF ALLOYS OR NON-FERROUS METALS

PROBLEM TO BE SOLVED: To provide a high strength hot-dip galvanized steel sheet in which generation of a crack can be suppressed even at a place such as a bent portion where the steel sheet has extremely large quantity of strain and which is excellent in balance of strength and formability, and a method of producing the high strength hot-dip galvanized steel sheet.SOLUTION: The high strength hot-dip galvanized steel sheet comprises: a base material having a component composition containing C:0.11 mass% to 0.28 mass%, Si:0.01 mass% to 3.0 mass% and Mn:0.7 mass% to 3.5 mass% and the balance iron with inevitable impurities; and a galvanized layer cladding a surface of the base material, the base material has a decarburized layer ranging from a boundary surface with the galvanized layer to a region 10 μm or more in a base material depth direction and having a C concentration of 0.07 mass% or less. The number of dot-like non-galvanized defects with a diameter of 50 μm to 250 μm in the galvanized layer is preferably 0.1/mmor less.SELECTED DRAWING: None 【課題】曲げ加工部のような歪み量が極度に大きくなる箇所でも亀裂の発生を抑制することができ、強度と成形性とのバランスに優れる高強度溶融亜鉛めっき鋼板及び高強度溶融亜鉛めっき鋼板の製造方法を提供する。【解決手段】本発明の高強度溶融亜鉛めっき鋼板は、Ｃ：０．１１質量％以上０．２８質量％以下、Ｓｉ：０．０１質量％以上３．０質量％以下、Ｍｎ：０．７質量％以上３．５質量％以下を含有し、残部が鉄及び不可避的不純物からなる成分組成を有する母材と、この母材の表面を被覆する亜鉛めっき層とを備え、上記母材が、上記亜鉛めっき層との界面から母材深さ方向に１０μｍ以上に亘り、Ｃ濃度が０．０７質量％以下の脱炭層を有することを特徴とする。上記亜鉛めっき層における直径５０μｍ以上２５０μｍ以下の点状の不めっき欠陥の数としては０．１個／ｍｍ２以下が好ましい。【選択図】なし