PRE 를 향상시키는 Mo의 역할을 유지하기 위해 용접부의 PRE가 모재보다 더 낮은 상황을 허용하지 않기 때문이겠지요. 다만, chloride environment를 위한 SSS (super SS : PRE > 40) welding 이나 Fatigue Stress가 문제가 되는 MSS or FSS Welding 을 위해, 또는 Dissimilar Welding이나 Hardfacing을 위한 Buffer Layer를 위해 자주 사용되는 Alloy 625 (ENiCrMo-3)는 이들 모재에 비해 상당히 고급재료이고 고가이나 적당한 중간 용접재료가 없어 어쩔 수 없이 사용되는 경우라고 보면 될 겁이다.

안녕하세요. 답변 감사합니다. 참고로 ukwelder.com 에 아래와 같이 문의를 하였고 Dear sirs Now I am planning to make PQR for ASTM A312 UNS S31254 Piping Material. I found that Welding Consumables like ERNiCrMo-3/ENiCrMo-3 are recommended on many welding handbooks and/or welding manuals. While I checked Welding Consumable "ER385". Chemical composition of "ER385" is almost similar to UNS S31254 and further ER385 is having about 8% Nickel content more than UNS S31254. Note. As per client Specification, Corrosion Test as per ASTM G48 is required. I want to know why "ER385 is not recommended to use for UNS S31254 material"? I am looking forward to seeing prompt & more technical reply from you shortly. 아래와 같이 답변을 받았습니다. The 31254 is Sandvik 254SMo and they recommend the Nickel Alloy....its difficult to go against the recommendation of the manufacturer who has done many tests (I assume) I believe the reason is that the Nickel Alloy more than matches the pitting corrosion resistance of the 254SMo whilst the 904L (ER385) falls slightly short. Its the Cr / Mo content that is the important factor. Also the 904L could, under extremely high restraint, suffer from solidification cracking. attached is the Sandvik data sheet which compares the corrosion properties of 254SMo v 904L https://www.materials.sandvik/en-gb/materia...andvik-254-smo/ Regards 즐거운 하루 되십시요

Hi Mr. Lee, I believe you have a good answer from ukwelder.com Here are some more notes related with welding and corrosion for your better understanding. As you know very well, there are several methods to avoid the solidification cracking in welding of stainless steels.. Most super ASS (SASS) have low Creq/Nieq ratio (about 0.9 to 1.2) and no ferrite content while most 300 series SS (ASS) have the higher Creq/Nieq ratio (about 1.2 to 1.6) and some ferrite (0-20% for base metal and fillers) before solution heat treatment. Kujanpaa’s diagram (1979) and Lundin’s diagram (1988) indicate that SASS will be more susceptible to solidification cracking than that of ASS. Those diagrams suggested to control the Creq/Nieq ratio and/or (P+S) wt% control to avoid the solidification cracking. Also, many reports and codes/standards suggest and require to control the ferrite contents (3-11 FN for ASS) in the weld metal to avoid the solidification cracking because free S & P in the matrix can be greatly reduced due to the presence of ferrite.. Therefore, the welding of super ASS typically requires to control the (S + P) contents < 0.01% while the welding of 300 series SS requires the ferrite control (3-11% FN). The similar and dissimilar joints of super ASS can be successfully welded under the (S + P) control. Once Alloy 625 is used, no chemical and ferrite controls are required. Nevertheless, the primary consideration in this situation should be the corrosion resistance. (material selection) for the weld joint. The CPT of two metals, 254SMO and 904L (ER385) in ASTM G150, 1M NaCl solution shows 30 deg.C difference which is very high. Therefore, the use of ER385 is typically not acceptable. You can refer to my books and lecture slides which show more detail backup data and references. If you need more discussion, please do not hesitate to email me. Thomas Eun/USA thomaseun at yaoo.com