WELDING 2-1/4% Cr-1% Mo STEEL TUBES TO 2-1/4% Cr-1% Mo STEEL TUBE-SHEETS. Final Report
The investigation reported presents the results of a program whose aim was the development of a reliable and reproducible procedure for welding tubes to tubesheets comprised of 21/4% Cr-1% Mo steel. Of the three basic types of welding processes evaluated, the inert-gas-shielded tungsten-arc (nonconsumable electrode) process proved to be the most applicable for welding these tubes to tubesheets. Compared to the inert-gas-shielded metal-arc and manual metal-arc processes, the superior applicability of the inert-gas-shielded tungsten-arc process was evident by the readily obtainable reproducibility in regard to uniformity and weld quality, as well as greater operator appeal due to the more easily controlled weld puddle. Weld quality with the tungsten-arc process was found to be appreciably influenced by such factors as base-metal-surface oxides, composition and size of welding wire, and welding current. Satisfactory results were obtained by thoroughly cleaning prior to welding the metal areas forming the joint, the use of a 3/32-in.-diameter wire having a silicon content ranging from 0.34 to 0.50% and through the application of sufficient current to insure proper fusion and penetration. Because the metals involved are air-hardening and have limited ductility in the as-welded condition, various preand post-heat treatments were conducted to establish the most applicable combination to use, consistent with obtaining the maximum possible ductility as measured in terms of DPH hardness. Welding preheat-temperatures of 70, 200, and 400 deg F were evaluated followed by postweld heat treatments at 1325 deg F for periods of 1 and 6 hr. The 200 deg F preheat, selected for the final recommended welding procedure on the basis of hardness determinations, resulted in a maximum heat-affected zone hardnesses of 270 DPH after welding. Postweld heat treatments for 1 and 6 hr at 1325 deg F tempered this maximum hardness to 232 and 206 DPH, respectively. The 6-hr heat-treatment was necessary since the entire boiler section, of which the tube-totubesheet weldment is a component, was postheat treated as a unit. The result of a 6-hr time period at 1325 deg F was entirely satisfactory, as reflected in the 206 DPH value obtained. As a final reliability check, two prototype tube-totubesheet assemblies are currently being thermally fatigue tested. (auth)
- Research Organization:
- Alco Products, Inc., Schenectady, N.Y.
- DOE Contract Number:
- AT(11-1)-666
- NSA Number:
- NSA-15-011537
- OSTI ID:
- 4084553
- Report Number(s):
- APAE-73
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-61
- Country of Publication:
- United States
- Language:
- English
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