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Nickel to Stainless Dissimilar Metal Welding

Nickel to Stainless Dissimilar Metal Welding. Kristopher Doll. Nickel to Stainless Dissimilar Metal Welding Project Objectives. Assess mechanical properties of a 316 to 718 weld Determine relationship of groove design to root penetration.

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Nickel to Stainless Dissimilar Metal Welding

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  1. Nickel to Stainless Dissimilar Metal Welding Kristopher Doll

  2. Nickel to Stainless Dissimilar Metal Welding Project Objectives • Assess mechanical properties of a 316 to 718 weld • Determine relationship of groove design to root penetration

  3. Nickel to Stainless Dissimilar Metal Welding Presentation Overview • Base and Filler Metal Properties • Welding Concerns • Experimental Results • Hardness Survey • Transverse Weld Tensile Test • Groove Geometry

  4. Base and Weld Metal Properties * www.matweb.com ** Special Metals Corporation, INCONEL alloy 625 and INCONEL alloy 718

  5. 316 to 718 Welding Concerns Estimated Fusion Zone Composition with 625 filler • Base Metal Dilution • Typically 20-50% for GTAW • Determined chemically or by cross sectional area • Reduces mechanical properties and corrosion resistance Image: Avery, R. Pay Attention to Dissimilar Metal Welds. Chem. Eng. Prog. (1991)

  6. Nickel Alloy Welding Concerns • Root Penetration • Nickel has high viscosity and low thermal conductivity • Weld pool is “Sluggish” • Solidification Shrinkage • Weld Craters • Must gradually decrease heat input

  7. 718 Welding Concerns • Microfissuring • Low heat input  Grain boundaries melt and crack • Laves Phase • High heat input  intermetallic precipitates Gordine, J. Some Problems in Welding Inconel 718. Welding Research Supplement. 1971

  8. Groove Design for 718 Groove Shape Root Opening Gordine, J. Some Problems in Welding Inconel 718. Welding Research Supplement. 1971

  9. Welding Approach Welding Parameters Recommended Welding Parameters(For 1/2” plate with GTAW)

  10. Preliminary Experiments 60° V no root gap 60° V .03” root gap 90° V .03” root gap Weld did not reach root Incomplete Fusion Un-fused weld metal in root gap

  11. 177 138 108 88 75 Weld and HAZ Hardness Survey Nickel 718 Nickel625 Stainless 316 Weld Approximate UTS (ksi) HRA Before Welding Reported UTS (ksi)from Technical Literature

  12. Transverse Weld Tensile Test 316 718 316 Properties Derived from Test Reported Dissimilar MetalWeld Tensile Strength * *Reference: Special Metals Corporation, INCONEL alloy 625

  13. Root Penetration Experiment U Groove 718 316 718 316 90° Chamfer 718 316 718 316 Increasing Root Gap

  14. Summary of Results • HAZ and Dilution • Solutionized 718 gets stronger in HAZ • Dilution reduces strength of fusion zone • 316 approaches annealed properties in HAZ • Transverse weld tensile strength • 92 ksi with ductile failure in weld zone • Root penetration • Very sensitive to welding technique • U-grooves superior for small root gaps. • No significant difference for large root gaps.

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