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Coil Joining Using HFIW

Background. Flash Butt Welding (FBW) vs. High Frequency Induction Welding (HFIW)ADVANTAGES of FBW:Well known, widely used process for coil joiningSimple and reliable operationGood productivity and repeatability DISADVANTAGES of FSWSensitive to edge fitup, current-path dependent, edge-to-edge h

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Coil Joining Using HFIW

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    1. Coil Joining Using HFIW Dr. Y. Adonyi Professor, Omer Blodgett Chair of Welding and Materials Joining Engineering

    2. Background Flash Butt Welding (FBW) vs. High Frequency Induction Welding (HFIW) ADVANTAGES of FBW: Well known, widely used process for coil joining Simple and reliable operation Good productivity and repeatability DISADVANTAGES of FSW Sensitive to edge fitup, current-path dependent, edge-to-edge heat input variations Becomes less effective when sheet becomes thinner, wider and has higher strength

    3. This is a bird’s eye view of the weld area. The water coolant has been shut down to allow the picture to be taken. Without proper cooling, the welding process would not continue very long. However, one part of the weld that does not need coolant is the vee. Water in the vee only robs the edges of heat and may float debris into the weld area. Keep the coolant out of the vee.This is a bird’s eye view of the weld area. The water coolant has been shut down to allow the picture to be taken. Without proper cooling, the welding process would not continue very long. However, one part of the weld that does not need coolant is the vee. Water in the vee only robs the edges of heat and may float debris into the weld area. Keep the coolant out of the vee.

    4. HFIW Fundamentals Capabilities: 0.005” wall thickness to 1” at 50 kW to 1 MW power, 100-800 kHz freq. Stationary inductor coil and impeder, moving base metal Applied mostly for tubular products made of Steel, Al, Cu, SST

    5. The photo on the left shows a typical HF weld. The ferrite bond line is barely visible (arrow). The picture on the right is the weld area after it has been heated in the induction line.The photo on the left shows a typical HF weld. The ferrite bond line is barely visible (arrow). The picture on the right is the weld area after it has been heated in the induction line.

    6. It is extremely important to understand that the HF weld is not like an arc weld. The edges are not melted and allowed to flow together, rather the molten metal is squeezed out. The hot metal under the molten metal is then forged together. This squeezing out of the molten metal forces all the oxidized metal out of the weld. Failure to achieve adequate squeeze out will leave oxides and molten metal on the bond plane. Even when proper squeeze-out is achieved, vee geometry and the speed/power ratio can still conspire to form weld defects.It is extremely important to understand that the HF weld is not like an arc weld. The edges are not melted and allowed to flow together, rather the molten metal is squeezed out. The hot metal under the molten metal is then forged together. This squeezing out of the molten metal forces all the oxidized metal out of the weld. Failure to achieve adequate squeeze out will leave oxides and molten metal on the bond plane. Even when proper squeeze-out is achieved, vee geometry and the speed/power ratio can still conspire to form weld defects.

    7. Macro views, laboratory samples

    8. Erichson Cup Height Changes

    9. Hardness Distribution across HFIW

    10. INITIAL CONCLUSIONS (July 2005) While some loss of ductility and gain in strength were observed, HFIW emerges as the best joining technology for USSK grades Focused R&D effort is worth initiating with HFIW manufacturer for full scale implementation: HFIW could apply to all future grades HFIW is similar in pre-post weld operations to FBW HFIW can offer more process control for lighter gauges (variable frequency feature)

    11. What Would this New R&D Effort Buy USSK? Widen optimum welding operational envelopes for joining traditional- and advanced- steels (reliability); Better accommodate thin/thick and different strength grades (flexibility); Possibility for selling the on-line welds (quality);

    12. Basic Concept

    13. Follow-up Experiments, LU HFIW alone Hybrid HFIW + FBW HFIW preheat + FBW completion Alternate (HFIW + FBW) cycles Post Weld Heat Treatment (PWHT) using HFIW Measure EMI caused by HF on the Gleeble Use thermocouple vs. infrared device for feedback

    14. Gleeble, 3/8”dia. Steel, HF coil

    15. Radio frequency interference test

    17. FBW only

    18. HFIW+FBW

    19. Conclusions HFIW and FBW welding simulations are possible in the Gleeble The HFIW+FBW hybrid joint had better quality than the FBW alone The HFIW system did not interfere with the Gleeble controls in the 200-400 kHz range and 1 kW power

    20. Future Work Acquire a 5-10 kW variable frequency HFIW unit, 200-800 kHz. Use flat sheet 1-2” wide, 1/8” thick, modify inductor coil geometry and use austenitic SST jaws Experiment with HFIW/FBW sequences Write proposal for off-line full scale coil joining model.

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