[ Column ]
Figure 2 . MAG welding an austenitic stainless steel frame .
better weld penetration and increases fluidity of the weld pool and CO 2 increases and broadens penetration .
Ferrite calculation Welding standard austenitic stainless steels requires keeping the ferrite level high enough so that it resists cracking but low enough to prevent transforming to a brittle phase or possible selective attack . To determine balance between the austenite and ferrite forming elements in iron , engineers use one of three constitution diagrams : Schaeffler ( the original ), DeLong or WRC-1992 , and it is the latter one that is the most preferred . Static charts are widely available , but online and mobile applications allow users to easily switch between diagram options , enter variables ( e . g ., percentage of carbon , chromium , molybdenum , nickel , nitrogen , etc .) and obtain results .
Heat input To preserve metallurgical properties , some applications require calculating heat input , which may be a maximum , minimum , or both . For example , with a 2205 duplex alloy , welding below the minimum heat input can result in the wrong phase balance after welding , while excess heat can also affect the corrosion resistance or embrittle the metal . Measured in kJ / mm , heat input requires knowing the values of current , voltage , weld length and arc time . The formula is :
Heat Input = ( Amps × Volts ) / ( 1,000 × travel speed in mm / s ) = kJ / mm
Over-welding often causes distortion and excess heat input . Rather than reducing volts or amps , a better solution could be increasing travel speed to yield a more ideal bead profile . Some stainless filler metal grades have existed for years , but new ones are being developed to meet the requirements of changing metallurgies , more extreme service conditions , higher yield strength and cost constraints . As a result , even experienced fabricators can benefit by consulting a filler metal expert and leveraging resources such as filler metal data books and online applications .
www . stainless-steel-world . net Stainless Steel World November 2022 21