Metal service temperature

These compounds are the next stop up in strength and general service in hot-melt adhesives. These so-called high-performance hot melts are used to assemble products made from glass, hardboard, wood, fabric, foam, leather, hard rubber, and some metals. Service temperatures range from 0°C to about 82°C. A number of formulations are available that can be used at >93 °C. Some are capable of being used in non-load-bearing applications at>149°C. ... 

Service temperature limitations must be considered in the use of composites, not only in the selection of polymer and process, but sometimes in the selection of the reinforcement as weU. Composites cannot generally perform as weU as metals or ceramics in very high temperature appHcations, but they can be made fire resistant to meet most constmction and transportation codes. 

Careflil material selection is required to prevent brittle failure of tanks at low temperatures. In addition, for tanks where the service temperatures are reduced, it is essential that an engineering analysis be performed to ensure that the tanks are not subject to brittle failure at the house temperature. The tank and vessel codes usually specify allowable materials based on design temperature. Further information about selection of metals for low temperature is available (8). 

With higher mol ding speeds and higher temperature resins, the demand for thermal stabiUty is increasing. As plastics replace metals in automotive apphcations, weatherabihty and service-temperature requkements are sharply increased. SuppHers are responding with improved products. 

Compounds based on S—EB—S usually contain polypropylene, which improves solvent resistance and processibiUty and raises upper service temperatures. Compounds intended for use in the automotive industry are able to survive 1000 hours air exposure at temperatures of 125°C with only minor changes in properties (54). Very soft compounds have been developed to replace foam mbber for interior trim parts. In this and similar appHcations, these soft compounds are usually insert molded over polypropylene or metal and then coated with flexible polyurethane paint (55). Other automotive appHcations include products intended for sound deadening, flexible air ducts, and gear shifter boots, as weU as improving the properties of sheet mol ding compounds. 

In addition to epoxy-phenolic adhesives three-part epoxy-phenolic-nitrile rubber systems are used in metal-metal edge joints and honeycomb constructions [208], These add toughness not available in most EP systems and improve peel strengths. When used on honeycomb, the NR-P is normally applied to the aluminum skin and the EP to the honeycomb for assembly. Service temperature limitations are those imposed by the NR-P part. 

It has been shown throughout this chapter that the properties of plastics are dependent on time. In Chapter 1 the dependence of properties on temperature was also highlighted. The latter is more important for plastics than it would be for metals because even modest temperature changes below 100°C can have a significant effect on properties. Clearly it is not reasonable to expect creep curves and other physical property data to be available at all temperatures. If information is available over an appropriate range of temperatures then it may be possible to attempt some type of interpolation. For example, if creep curves are available at 20°C and 60°C whereas the service temperature is 40°C then a linear interpolation would provide acceptable design data. 

During the materials selection procedure isothermal corrosion testing may indicate the suitability of a material for handling a corrosive process fluid. In many cases where heat transfer is involved the metal wall temperature experienced in service is higher than the bulk process fluid temperature. This, and the actual heat transfer through the material, must be taken into account since both factors can increase corrosion rates significantly. 

For service temperature above 454°C (850°F), weld metal shall have a carbon content above 0.05%. 

Fluorocarbon elastomers, such as copolymers of VDF and HFP, typically have a maximum continuous service temperature of 215°C (419°F). Some metal oxides may cause dehydrofluorination at a temperature of 150°C (302°F) or even lower.16 Copolymers of VDF and CTFE (e.g., Kel-F ) have a maximum long-term service temperature of 200°C (392°F). Fluorocarbon elastomers based on copolymers of VDF/HPFP (hydropentafluoropropylene) and on terpolymers of VDF/HPFP/TFE have lower thermal stability than copolymers of VDF/HFP because they have a lower fluorine content than the latter.17 A detailed study of thermal stability of fluoroelastomers was performed by Cox et al.18... 

Ni brazes are attractive when components must endure high service temperatures and evaluation of the potential of Ni eutectic brazes containing additions of Cr, such as BNi-5 and BNi-7 (Ni-19Cr-1 OSi and Ni-14Cr-10P), as the active metal for joining Si3N4 and SiC ceramics has been vigorous, (McDermid et al. 1989,... 

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