Effect of welding technique on weld morphology and hardness of supermartensitic 13%Cr steels

Abstract

The 13%Cr supermartensitic stainless steels are a new group of steels for use as pipelines for oil and gas transport. Sheet and strip material from the supermartensitic stainless steels containing 11 . 5-12%Cr and different Ni (4 . 6 and 6 . 4%) and Mo (1 . 3 and 2 . 3%) contents were welded using several techniques including Plasma/TIG, EB and EB/ TIG. Post-heat treatment was also applied. The effect of welding technique on the weld morphology and hardness distribution was studied. The structure obtained included a variety of phases which are roughly identified as ferrite and austenite with Ni, Cr, Mo and Si in solid solution with the absence of conventional martensite owing to the very low carbon content of the steels. Hardness values as high as 350 HV were obtained in the fusion zone in the EBzTIG/tempered and in PlasmazTIG/tempered states, whereas it reached 360-370 HV in the fusion zone in EB with and without filler independent of the composition. A lower hardness of around 300 HV was obtained in the fusion zone of PlasmazTIG/tempered and Plasma zTIG/as welded in the alloys containing lower Si (0 . 177%) and higher Mn (1 . 76%).MST/6023

Comparative study of hardfacing of valve seat ring using MMAW process

“…During the past two decades, as an improvement to existing 13% Cr alloys, various applications in the industries for 15-18% Cr as a welded deposit have increased markedly across medium to heavy industries (Neubert et al, 2004). Most of the common hardfacing alloys are based on iron, many times containing large additions of chromium and carbon.…”

Effects of post weld heat treatments on the microstructure and mechanical properties of dissimilar weld of supermartensític stainless steel

“…Neubert et al 10 have studied several welded joints of 12%Cr SMSS produced by high energy processes, and found a slight increase of hardness with short time post weld tempering in the 630-640 °C range. On the other hand, Thibault et al 11 measured a slight decrease of hardness in weld metal and heat affected zone (HAZ) in a 13Cr-4Ni A supermartensitic stainless steel with composition 12.2%Cr-5.8%Ni-1.90%Mo-0.028%C (%wt.)…”

GTAW of 12% Supermartensitic Stainless Steel Using 625 Nickel Alloy as Filler Metal

“…On the other hand, the joints in pipelines for oil and gas transportation are all made by welding. For this reason, some important research works about welding and weldability of supermartensitic stainless steels have been developed [6][7][8][9][10][11][12][13] , some of them envisaging new applications for this type of steel, such as in pipelines.…”

“…According to Lippold and Kotecki 1 , SMSS may be welded with similar feed metal or with austeno-ferritic steel (duplex or superduplex). The works of Pereda et al 14 , Zappa et al 7 , Ramirez 8 , Thibault et al 9 and Neubert et al 10 are examples of researches about welds produced with similar feed metal. The main difficulty is to find a commercial feed metal which matches perfectly with the composition of the SMSS to be welded.…”

“…The goals of PWHT are the reduction of peak of hardness in the heat affected zone (HAZ) and stress relief [7][8][9] . Although Neubert et al 10 have found a slight increase of hardness of 12%Cr SMSS with short time post weld tempering in the 630-640°C range, other works reported the decrease of the HAZ hardness with PWHT in the 600-650 o C range [7][8][9]11 . Divya et al 16 obtained significant reduction of hardness in weld metal obtained with ER 414NiMo through single and double PWHT.…”