Ni Weld Metal Research Articles

Aspect ratios and morphology of acicular ferrite in C–Mn–Ni weld metals

The aspect ratio and morphology of acicular ferrite formed in C–Mn–Ni weld metals and the effect of nickel and oxygen contents have been investigated. The experimental results revealed that nickel has a strong effect on the acicularity of acicular ferrite in C–Mn–Ni weld metals. High nickel contents resulted in sharper acicular ferrite laths with a larger aspect ratio. It is considered that the two dominant mechanisms are the role of nickel in changing the balance of incoherent/coherent growth ledges, and the transformation temperatures at which this growth takes place. Reducing the oxygen content in the weld metals was also found to increase the aspect ratio.MST/3071

Aspect ratios and morphology of acicular ferrite in C–Mn–Ni weld metals

The aspect ratio and morphology of acicular ferrite formed in C–Mn–Ni weld metals and the effect of nickel and oxygen contents have been investigated. The experimental results revealed that nickel has a strong effect on the acicularity of acicular ferrite in C–Mn–Ni weld metals. High nickel contents resulted in sharper acicular ferrite laths with a larger aspect ratio. It is considered that the two dominant mechanisms are the role of nickel in changing the balance of incoherent/coherent growth ledges, and the transformation temperatures at which this growth takes place. Reducing the oxygen content in the weld metals was also found to increase the aspect ratio.MST/3071

Hot cracking and micro-segregation in 18–10 stainless steel welds

AbstractAdvanced quantitative chemical and image analysis techniques based on scanning and scanning-transmission electron microscopy have been used to study hot cracking and micro-segregation in an 18%Cr-10%Ni weld metal. It is found that the main cause of hot cracking is sulphur segregation. In fully austenitic welds, manganese remains in solution and when the last of the S-rich melt solidifies Mn is simply not available to break up the sulphide films. The present practice of substantially increasing the amount of Mn in austenitic welds, or adding cerium, would thus seem to be justified. Phosphorus also aggravates the problem of hot cracking, but fortunately it does not appear to segregate so markedly as sulphur, being much more soluble in austenite. If the weld metal is so alloyed that solidification to the two-phase austenite plus ferrite occurs, hot cracking does not occur. The two main reasons are concluded to be: (1) manganese is less soluble in ferrite than austenite and a sufficient quantity of Mn...

異種金属溶接部の炭素の移動

The present study was carried out to make clear the C migration in dissimilar metal welded joint at high temperature. To prepare test pieces, C steel and 2 1/4 Cr-1 Mo steel plates were welded with eight kinds of ferritic electrodes, 1/2 Mo, Cr-Mo Cr-Mo-V etc. and eight kinds of ferritic steel plates were welded with two kinds of sustenitic electrodes and 2 1/4 Cr-1 Mo steel was welded with Inconel electrode. These dissimilar welded joint specimens were heated at 500-800°C for 1-3, 000 h and then observed microscopically. The results are summerized as follows :(1) C in lower Cr steel migrated to higher Cr steel and carbides precipitated in higher Cr steel along fusion line. At higher temperatures, the ferrite grains coarsened in decarburized zone.(2) C migration was promoted with increase of Cr content in higher Cr steel and addition of V.(3) C migration was reduced with increase of Cr content in lower Cr steel and addition of V.(4) In the welded joints of Cr-Mo weld metals to C steel, the width of carbides precipitated zone increased with increase of Cr content in Cr-Mo weld metals up to 3 Cr-1 Mo steel and decrease with the increass of Cr content more than 3 Cr-1 Mo steel. The distribution density of carbides increased with the increase of Cr content in Cr-Mo weld metals.(5) The extent of C migration with 25 Cr-20 Ni weld metal was slightly more than 16 Cr-8 Ni-2 Mo weld metal. The extent of C migration with Inconel weld metal was less than those with 16 Cr-8 Ni-2 Mo and 25 Cr-20 Ni weld metals.