Fitting part having excellent resistance to hydrogen induced cracking and manufacturing method for the same

• Main Author: KIM DAE WOO
• Format: Patent
• Language: English; Korean
• Published: 01.07.2021
• Subjects: ALLOYS; CHEMISTRY; FERROUS OR NON-FERROUS ALLOYS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS; MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS; MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVINGMATERIAL; METALLURGY; METALLURGY OF IRON; MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; PERFORMING OPERATIONS; PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OFWROUGHT-IRON OR STEEL; PUNCHING METAL; ROLLING OF METAL; TRANSPORTING; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS

A fitting part according to one aspect of the present invention comprise: 0.06 to 0.25 wt% of C; 0.05 to 0.5 wt% of Si; 1.0 to 2.0 wt% of Mn; 0.005 to 0.4 wt% of Al; equal to or less than 0.01 wt% of P; equal to or less than 0.0015 wt% of S; 0.001 to 0.03 wt% of Nb; 0.001 to 0.03 wt% of V; 0.001 to 0.03 wt% of Ti; 0.01 to 0.2 wt% of Cr; 0.05 to 0.15 wt% of Mo; 0.01 to 0.5 wt% of Cu; 0.05 to 0.5 wt% of Ni; 0.0005 to 0.004 wt% of Ca; equal to or less than 0.001 wt% of O; and the remaining of Fe and inevitable impurities. A composite structure of pearlite and ferrite is included as a microstructure. The segregation degree (S_Mn) of manganese in a core part defined by the following relation1 can satisfy a value equal to or less than 1.3. The relation1 is S_Mn= Mn_max/ Mn_ave, wherein Mn_max represents the maximal concentration of manganese (Mn) in the central part of a section and Mn_ave represents the average concentration of manganese (Mn) in the central part of the section. 본 발명의 일 측면에 따른 피팅부품은, 중량%로, C: 0.06~0.25%, Si: 0.05~0.5%, Mn: 1.0~2.0%, Al: 0.005~0.4%, P: 0.01% 이하, S: 0.0015%이하, Nb: 0.001~0.03%, V: 0.001~0.03%, Ti: 0.001~0.03%, Cr: 0.01~0.2%, Mo: 0.05~0.15%, Cu: 0.01~0.5%, Ni: 0.05~0.5%, Ca: 0.0005~0.004%, O: 0.001%이하, 나머지 Fe 및 기타 불가피한 불순물을 포함하고, 펄라이트 및 페라이트의 복합조직을 미세조직으로 구비하며, 하기의 관계식 1로 정의되는 중심부 망간 편석도(SMn)가 1.3 이하를 만족할 수 있다. [관계식 1] SMn = Mnmax / Mnave 상기 관계식 1에서, Mnmax 은 단면 중심부에서의 최대 망간(Mn) 농도를 의미하며, Mnave는 단면 중심부에서의 평균 망간(Mn) 농도를 의미한다.