tailieunhanh - Arc Welding 2011 Part 9

Tham khảo tài liệu 'arc welding 2011 part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 8 Evaluation of the Shielding Gas Influence on the Weldability of Ferritic Stainless Steel Demostenes Ferreira Filho1 Ruham Pablo Reis1 and Valtair Antonio Ferraresi2 1Federal University of Rio Grande School of Engineering 2Federal University of Uberlândia Faculty of Mechanical Engineering Brazil 1. Introduction The use of stainless steels has been nowadays widespread in a number of industrial sectors. They usually offer exceptional performance regarding mechanical and corrosion properties but according to Lee et al. 2008 stainless steels are considered as high cost materials as far as solutions for structural engineering are concerned. However this material group can provide aesthetic characteristics as well as outstanding versatility easy cleaning and maintenance conditions. Nevertheless there are still plentiful possibilities for applying stainless steels in new situations or improving their use in current applications due to their appealing visual aspect and durability. In the automotive industry for instance parts of the exhaustion system are in general composed of tubes and blanks stamped metal sheets that usually are welded and have ferritic stainless steels as the main base material. According to Alves et al. 2002 the main ferritic stainless steels used in the hot portion of automotive exhaustion systems are the AISI 409 and 441. On the other hand in the cold portion the AISI 409 439 and 436 are normally utilized. Faria 2006 states that automotive exhaustion systems went through a number of changes along the last 20 years as a consequence of more restrict pollution policies needs for longer durability and higher engine efficiencies as well as requirements for reduction in weight and costs. Stainless steels used in the hot parts of automotive exhaustion systems according to Sekita et al. 2004 must be refractory which can be accomplished by niobium additions high levels of molybdenum and optimized silicon presence. The same authors also mention the importance