Introduced T9l/P91 steel development process, analysis of the main problems of the Carbon Steel Welding Electrode, welding of the steel elements and its application. The results show that, T9l/P91 a series of new steel for its excellent use of types of performance parameters of thermal power generating units in high heat pipe to obtain a wide range of applications. Welding of the steel main problem is a strong sensitivity to cold cracking, and a certain tendency to hot cracking, but also the weakening of joint properties can not be ignored (weld metal and HAZ toughness deteriorated softening); reasonable control of the welding process is and improve the weldability of the steel key technical means. Welding method and welding material is determined, access to quality measures for key process joints are: preheat, the control layer temperature, and the "timely and effective," the weld heat treatment process. Combination of different connector types (the same kind of steel or dissimilar steel), different sizes of T91/P91 steel pipe welding, the welding process of matching individual features; using special flux cored wire filled with TIG backing new technology, the steel welding process to a new stage of development.
T91/P91 durable steel with good high temperature strength, thermal stability and high temperature creep resistance and other comprehensive performance in power plant boiler superheater, reheater, and the main steam pipe to obtain more and more widely applied. Although T91/P91 use and research of steel in China has been more than a decade, a number of units in the control of the steel welding process has accumulated some experience and power by the State Power Corporation under the Ministry of Construction made a "T91/P9l steel welding guide the "guiding document, but the welding at the construction site, the quality of the welding of steel still occur. This indicates that, on the one hand the understanding of the weldability of steel deep enough; the other hand, the key technologies supporting the control of welding process is not yet in place. In other words, the introduction of steel and welding process of digestion, absorption, and localization will be needed to continue. Steel welded on the research literature T91/P91 increasing year by year, the power plant units are all examples of successful application of welding technology and its use is closely related.
Because the combination of types of joints, the tube Dimensions (diameter and wall thickness) different, different Welding Electrodes are matched, and thus continue T9l/P91 steel welding process and its supporting research on the search for joint performance process control mechanism, core technology and innovation process is necessary. Therefore, this article specifically to the typical welded steel welding technology and the associated issues, comprehensive review of the steel characteristics and application of welding technology. The work on the promotion of welding process T91/P91 steel to further improve and improve the life of the boiler, has a positive significance and reference value.
The electrodes using oxyacetylene welding. Operation process is as follows:
(1) cleaning the workpiece, the welding surface is exposed metallic luster.
(2) take the flat welding position welding, this can be used with the proper tires for the cladding layer thickness control can be used to limit thick block.
(3) with a neutral flame preheating, Yan Xin Do not touch the surface, the distance to 25mm is appropriate.
(4) when the workpiece is heated to the proper temperature, the welding surface can be coated in a layer-specific flux, such as warm-up was appropriate flux, flux will bubble boiling, then the oxide surface flux will be cleared continue to be heated to solvent welding surface and covered with a transparent liquid state was that you can begin backing weld surfacing layer.
(5) The surfacing weld backing layer, using a neutral flame, stirring constantly with a backing electrode tip flux, and subsequently melted, tip constantly running, the speed of the Welding Electrode coincided with the speed of rendering the same. To ensure that the flux maintain the workpiece surface. When the rendering process is completed, the welding surface should be smooth to form a thin layer of primer alloy, the thickness of about lmm or so. Such as the preheating temperature is low, the molten metal can not hit the bottom of leveling, and the formation of the workpiece on the table hit the ball or bump.
(6) surfacing welding layer of carbide. Alloy layer in the rendering above, with the YD-type electrode welding, use a neutral flame (flame carbide can slant) tip in a smooth uniform surface on the move, the flame front alloy welding heat (careful not to touch the tip of Yan Xin alloy particles), the electrode in the molten matrix alloy, followed by carbide particles also fall together. Solidification of molten metal in the matrix before, we should arrange the particles, the alloy electrodes can be used left hand pull to get, or another person holding a grounding electrode or a graphite rod for pulling the stick, stir in a rapidly near the particles, so neatly arranged in uniform. Cladding layer thickness according to design requirements control.
(7) After welding the workpiece, on the non-ventilated areas, slow cooling, can not quench, Conditional used asbestos blankets cover.
(8) after the workpiece is cooled to room temperature, if necessary, the welding surface grinding to the required size and shape.
(9) cleaning the workpiece, to remove all the splashing, slag, etc. Welding operation properly, the surfacing layer logo is of satisfactory quality: after cooling, welding layer was shiny golden surface, surfacing layer and the substrate metal matrix alloy with good alloy particles tightly packed, and uniform, firmly embedded in the matrix metal in Welding Assembly. Hot or burning the flag is: red metal matrix cooled, exposing the black surface of the alloy particles, the consequence of impaired performance alloy particles, affecting life. Insufficient heating of the signs are: cooling, was dull silver, the metal matrix alloy and the substrate with poor surfacing tool after running off the danger of surfacing layer.