Compositions for Welding

When thick-walled hollow molded artieles and molded articles with a shape having thick-walled sections and thin-walled sections are produced, the molded article is produced in two parts. These parts are eventually eon-nected by welding. Alternatively, the two parts are placed in another mold so that they face each other at the parting lines. Then, molten resin is injected about the periphery of the opposed faces to connect the parts. This technique is addressed as insert molding, or overlap molding. Other welding methods include  

Pure crystalline PAs show an unsatisfactory weld strength. Thus, these materials cannot be used for parts requiring a high weld strength. In order to improve the weld strength, the compositions should contain crystalline and amorphous partially aromatic PAs.  

For example, 97% PA 6 and 3% of PA 6I/6T are uniformly mixed in advance, and kneaded to prepare pellets of a PA resin composition. Before further use and examination of their properties, the pellets are dried for 24 h under reduced pressure at 110°C.  

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Product Specification Level 2 composition for welded pipe. ... 

Nozaki M, Kuroe T. Polyamide composition for welding. US patent Application 20040087 735, assigned to E.I. du Pont de Nemours and Company, Wilmington, DE 2004. 

Welds on steelwork need special attention because of the different composition of weld metal and adjacent steelwork, the rough surface and spatter caused by welding and the presence of welding flux. The latter is often alkaline and destructive to many paints. It is necessary to clean thoroughly, preferably by reblasting for 25-50 mm each side of the weld, fare the rough metal and wash off residual flux. The cleaned surface should then be stripe coated with the primer used on the remainder of the surface. 

Consumable inserts may be used, provided they are of the same nominal composition as the filler metal and will not cause detrimental alloying of the subsequent weld deposit. The welding procedure using consumable inserts shall be qualified as required by para. GR-3.2.4. The consumable insert shall be used for welding the root pass of butt welded pipe components requiring complete weld joint penetration (CWJP) utilizing the GTAW or PAW processes. 

There is clearly a microstructural dependence, and studies on HAZs show corrosion to be appreciably more severe when the material composition and welding parameters are such that hardened structures are formed. It has been known for many years that hardened steel may corrode more rapidly in acid conditions than fully tempered material, apparently because local microcathodes on the hardened surface stimulate the cathodic hydrogen evolution reaction. (Bond)5... 

Polycrystalline diamond has been used for aluminum-matrix composites reinforced with particulate silicon carbide, boron carbide, or alumina. It also shows promise as a tool material for welding titanium, although this work is only in a preliminary stage. 

Table 7.7 Base-metal and friction stir weld (FSW) compositions for Ti-15-3...

A number, calculated from the chemical composition of the steel by means of an empirical formula, which summarises some aspect of the steel s behaviour, particularly its hardenability or its resistance to hydrogen cracking. The term may also be used for weld metals. 

MAJOR APPLICATIONS Protective coatings (for appliance, automotive primers, pipes, etc.). Encapsulation of electrical and electronic devices. Adhesives. Bonding materials for dental uses. Replacement of welding and riveting in aircraft and automobiles. In composites for materials in space industry, printed circuitry, pressure vessels and pipes. Construction uses such as flooring, paving, and airport runway repair. 

In the USSR, the E. O. Paton Institute of Electrowelding carries out systematic studies of the weldability of structural steels and alloys for cryogenic use and the development of new materials and technological processes for welding. In recent years, data have been obtained and summarized on the main types of steels and alloys, distinguished by their specific strength, structural composition, and alloying system. 

For welding of these steels, wires and electrodes of a higher Ni content can be employed. Welds having compositions similar to that of steel possess a satisfactory resistance to defect formation (e.g., pores and cracks) and a strength approaching that of the base metal, but are sensitive to stress raisers at low temperatures, since their Ni content is < 5%. 

Analyses were performed by the support of 0KB "Gidropress", Siemens and Westinghouse, including analyses of RPV metal samples for defining the chemical composition of welds metal, neutron fluence and critical temperatures. Annealing of the metal was performed. 

Nanstad R K, McCabe D E and Swain R L (1999), Evaluation of variability in material properties and chemical composition for Midland Reactor Weld WF-70, pp. 125-156 in Effects of Radiation on Materials 18th International Symposium, ASTM STP1325, R K Nanstad, M L Hamilton, F A Garner and A S Kumar, eds, American Society for Testing and Materials, West Conshohocken, PA. 

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