Zirconium welding

Boric acid Copper oxide (ic) Lithium chloride Lithium fluoride Potassium tetraborate Tributyl borate Zirconium potassium hexafluoride welding flux, gaseous Trimethyl borate welding fluxes, special Zirconium welding gas Oxygen... 

Zirconium weld metal may corrode preferentially when H2SO4 concentration is approximately 55% and higher. Heat treatment at 775 + 15°C for 1 h per 25.4 mm of thickness can be applied to restore the corrosion resistance approaching that of the parent metal. However, this high-temperature heat treatment is not suitable for equipment made of zirconium/steel-clad materials because of the large difference in thermal expansion coefficients between these two alloys. Heat treatment at a much lower temperature, such as 510 + 20°C, should be applied when there is... 

Eabrication techniques must take into account the metallurgical properties of the metals to be joined and the possibiUty of undesirable diffusion at the interface during hot forming, heat treating, and welding. Compatible alloys, ie, those that do not form intermetaUic compounds upon alloying, eg, nickel and nickel alloys (qv), copper and copper alloys (qv), and stainless steel alloys clad to steel, may be treated by the traditional techniques developed for clads produced by other processes. On the other hand, incompatible combinations, eg, titanium, zirconium, or aluminum to steel, require special techniques designed to limit the production at the interface of undesirable intermetaUics which would jeopardize bond ductihty. 

Pig. 10. Double-v inlay, batten-strap technique for fusion welding of an explosion-clad plate containing titanium and zirconium. 

Zirconium is completely resistant to sulfuric acid up to Foiling temperatures, at concentrations up to 70 wt %, except that the heat-affected zones at welds have lower resistance in >55 wt % concentration acid (Fig. 1). Fluoride ions must be excluded from the sulfuric acid. Cupric, ferric, or nitrate ions significantly increase the corrosion rate of zirconium in 65—75 wt % sulfuric acid. 

Zirconium resists attack by nitric acid at concentrations up to 70 wt % and up to 250°C. Above concentrations of 70 wt %, zirconium is susceptible to stress-corrosion cracking in welds and points of high sustained tensile stress (29). Otherwise, zirconium is resistant to nitric acid concentrations of 70—98 wt % up to the boiling point. 

Zirconium (Tin 1.2 to 1.7 Percent) Tubing is available seamless ranging from outside diameter by 0.030-in wall to 8-in outside diameter by 0.4-in wall, and welded up through 30-in outside diameter by VH-in wall. Cast valves and fittings are also available. 

Additions of zirconium confer a significant increase in corrosion resistance, particularly in sulphuric and hydrochloric acids . At alloying additions of the order of 50% Zr, however, there can be a significant diminution in resistance to oxidation and the welding of titanium to zirconium is not advisable, because within the welded zone the proportion of titanium to zirconium will almost inevitably fall within the sensitive composition range. 

It should be noted that swarf from a zirconium-titanium alloy containing approximately 50% by weight of each element is prone to pyrophoricity in air. It has also been reported that when zirconium is welded to titanium, the welded zone is much more sensitive to corrosion than either of the parent metals. If, therefore, it is proposed to use my construction in which zirconium is welded to titanium, caution should be observed in the machining of welds, and the corrosion behaviour of the weld should be checked by prior testing in the environment with which the construction will be employed. 

Uranium dioxide for use in nuclear fuel must be produced to a stringent specification so that it can be pressed into pellets and sintered at high temperature in hydrogen to produce dimensionally stable, crack-free UO2 pellets with a density typically 97% of theoretical. The fuel pellets are loaded into zirconium alloy tubes, welded closed and assembled into fuel bundles. 

Although stainless steel (SS) remains the most used cladding material, exotic materials such as titanium, zirconium or tantalum are finding increasing applications. Apart from plate-to-plate and tube-to-tube-plate, there are many other applications for explosive welding which are listed below. 

GOLDSCHMIDT REDUCTION PROCESS. Reaction of oxide), of various metals with aluminum lo yield aluminum oxide and the free metal. This inaction has been used to produce certain metals, e g. chromium and zirconium, from oxide ores and it is also used in welding (iron oxide plus aluminum giving metallic iron and aluminum oxide, plus considerable heat). (Thermite process. ... 

In addition to the Alloy 625 of the autoclave itself, the materials or material junctures examined were nickel (Ni) 201, platinum, platinum to Hastelloy C-276 weld in Zone 3, the YSZ supports, and arc-plasma sprayed YSZ on zirconium (thermal cycling only). The nickel, YSZ supports, and YSZ coating on zirconium exhibited poor performance (high corrosion, fracture, and delamination, respectively) in Zone 1 and Zone 2. Platinum was deemed to be satisfactory in Zones 1 and 3 but exhibited corrosive attack, including pitting and the formation of a platinum-sulfur compound, at the grain boundaries in Zone 2. The platinum/Hastelloy C-276 weld was determined to be satisfactory in Zone 3. 

The environments, along with the cracking modes of zirconium and titanium, are given in Table 4.88. It is obvious from the table that zirconium alloys are susceptible to stress-corrosion cracking in a variety of environments. It is necessary to subject the weld to heat treatment in order to lower the stress in the weld. The most serious problem encountered in the nuclear applications is delayed hydride cracking in addition to stress-corrosion cracking, particularly in Zr-2.5% Nb alloy. 

Corrosion-resistant metals and alloys, including stainless steels, nickel alloys, titanium, zirconium, and tantalum can be applied as linings or claddings to cheaper steel substrates. Most (>90%) are applied by roll bonding, but weld overlaying and explosive bonding are also used, as appropriate. Particularly expensive metals, such as tantalum, can be used as very thin ( 0.5 mm) loose linings. 

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