Effect of Heat Input and Shielding Gas Mixture on the Microstructure of Super Duplex Stainless Steel Welds

Super duplex stainless steel is steel that has a corrosion resistance and good mechanical strength so that used in industry especially in oil and gas and petrochemical industry. In use in the field is often used for the connection process by welding methods. To produce good welds, it should be noted that the welding procedures and parameters used , especially the heat input. In this study is used the heat input variables shielding gas composition to determine how much influence on the balance of ferrite - austenite phase structure in the weld stainless steels SAF 2507 super duplex with tungsten inert gas welding method (TIG). Heat input varied by applying different welding speed 1,3,4 and 5 mm /sec while the shielding gas is used 100 % argon, 98 % argon + 2 % nitrogen and 95 % argon + 5 % nitrogen. The result showed that at different welding speeds generated depth and width of the weld metal which is different. Likewise the use of protective gas will produce a different ratio wide and deep of weld metal which is different. By using protective gas 95 % argon + 5 % nitrogen squeak - ausenit phase, resulting in weld metal that is relatively balanced than others. On a slow welding in addition to produce a large heat input also produces weld metal hardness at high and affect the growth of the austenite phase. The higher the heat input ( 2,280 kJ / mm ) , the lower the austenite phase in the weld metal.

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The Effect of Welding Heat Input on the Structure–Property Relationship of a New Grade Super Duplex Stainless Steel

steel research international ◽

10.1002/srin.201900347 ◽

2019 ◽

Vol 91 (1) ◽

pp. 1900347 ◽

Cited By ~ 2

Author(s):

Milad Vahman ◽

Morteza Shamanian ◽

Mohammad Ali Golozar ◽

Ali Jalali ◽

Mohamad Ahl Sarmadi ◽

...

Keyword(s):

Stainless Steel ◽

Duplex Stainless Steel ◽

Heat Input ◽

Super Duplex Stainless Steel ◽

Structure Property ◽

Property Relationship ◽

Welding Heat Input ◽

Structure Property Relationship ◽

Relationship Of

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Effect of post-weld heat treatment on thermal diffusivity in UNS S32304 duplex stainless steel welds

Archives of Materials Science and Engineering ◽

10.5604/01.3001.0010.8039 ◽

2017 ◽

Vol 2 (88) ◽

pp. 49-58

Author(s):

E.G. Betini ◽

C.S. Mucsi ◽

T.S. Luz ◽

M.T.D. Orlando ◽

M-N. Avettand-Fènoël ◽

...

Keyword(s):

Heat Treatment ◽

Stainless Steel ◽

Thermal Diffusivity ◽

Duplex Stainless Steel ◽

Welding Process ◽

Austenite Phase ◽

Shielding Gas ◽

Heat Treated ◽

Steel Welds ◽

Weld Heat

Purpose: The thermal diffusivity variation of UNS S32304 duplex stainless steel welds was studied after pulsed GTA welding autogenous process without filler addition. This property was measured in the transverse section of thin plates after welding process and post-heat treated at 750°C for 8 h followed by air-cooling. Design/methodology/approach: The present work reports measurements of thermal diffusivity using the laser-flash method. The thermal cycles of welding were acquired during welding by means of k-type thermocouples in regions near the weld joint. The used shielding gas was pure argon and 98% argon plus 2% of nitrogen. The temperature profiles were obtained using a digital data acquisition system. Findings: It was found an increase of thermal diffusivity after welding process and a decrease of these values after the heat treatment regarding the solidified weld pool zone, irrespective of the welding protection atmosphere. The microstructure was characterized and an increase of austenite phase in the solidified and heat-affected zones was observed for post-weld heat-treated samples. Research limitations/implications: It suggests more investigation and new measurements about the influence of the shielding gas variation on thermal diffusivity in the heat-affected zone. Practical implications: The nuclear industry, especially, requests alloys with high thermal stability in pipes for power generation systems and safe transportation equipment’s for radioactive material. Thus, the duplex stainless steel grades have improved this stability over standard grades and potentially increase the upper service temperature reliability of the equipment. Originality/value: After heat treatment, the welded plate with 98%Ar plus 2%N2 as shielding gas presented a thermal diffusivity closer to the as received sample. By means of 2%-nitrogen addition in shielding gas during GTAW welding of duplex stainless steel may facilitate austenite phase reformation, and then promotes stability on the thermal diffusivity of duplex stainless steels alloys.

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