Stress-relieving processes

Stress relieving process of relieving stresses in an unassembled coiled spring through exposure to heat intended to help ensure that the spring force will not be adversely affected by heat during actual service. 

Figure 3.6 Axial forces applied in stress relieving process...

Insiilating refractories are used mainly in the heat-treating industiy for furnaces of the periodic type. They are also used extensively in stress-relieving furnaces, chemical-process furnaces, oil stills or heaters, and the combustion chambers of domestic-oil-burner furnaces. They usually have a hfe equal to that of the heavy brick that they replace. They are particularly smtable for constructing experi-... 

Alloy 600 Alloy 800 Water-cooled nuclear reactor circuits Usually IG 1. Control alloy composition and processing 2. Control water chemistry 3. Stress relieve after fabrication... 

Today, boilers are welded and stress-relieved, thus ostensibly eliminating a primary component of the SCC process however, modem boilers operate at higher heat fluxes, which imposes a strict requirement for cleaner metal surfaces. The presence of deposits on any waterside surface may provide an opportunity for the concentration of free alkali under the deposit, and so caustic embrittlement still occurs today, depending on inherent stress levels and the particular water chemistry involved. 

Stress Relieving. In this process, internal stresses are reduced by heating to a temperature below the critical range and holding it for a sufficient time I or equalization of the temperature throughout the piece. 

OTHER Maintenance 1. Equipment failure, flange leak, catalyst changeover in reactor, etc. Process stops. Ensure all pipes and fittings are constructed of the right materials and arc stress relieved. 

In almost all heat-treating processes, steel is heated above the point and then cooled at a rate that results in the microstmcture that gives the desired properties (34,37). Process annealing and stress-relieving are exceptions. 

Where +1/32 inch (+0.8 mm) has been the standard thickness tolerance for 4 foot (1.22 meter) wide panels produced in double belt lines, the standard for the fluid film process is +0.010 inch (+0.25 mm). At times, an accuracy within +.005 inch (+.127 mm) has been achieved. Such accuracy is possible because of the precision and rigidity of the tunnel construction. The platens are reinforced weldments, stress relieved after welding and then ground and chrome plated. They are separated by precise gage blocks to form the two faces of the tunnel. Deflection is practically non-existant since the foam pressure on the platen is balanced by the fluid pressure within the platen reservoir. The fluid film is accurately controlled to maintain it at a normal working thickness of 0.005 inch (0.127 mm). 

It can be assumed that coatings formed from lower crystallinity particles exhibit low residual stress because feedstock also has inherent porosity that would tend to relieve process-induced stresses. A comparison of the high velocity oxy-fuel and plasma spray processes has revealed that the residual stress is lower in the former process (Knowles et al. 1996). Heat treatment at temperatures of 800°C can minimize these process-induced stresses (Brown et al. 1994). Despite the large influence of thickness on coating strength, no difference in bone apposition has been found for 50 pm and 100 pm coatings. 

If there is a danger of electrolyte-induced atomic hydrogen formation and it is not possible to eliminate the electrolyte by drying, the use of steel as soft as possible and careful stress-relieving annealing of the components should be considered. Since austenitic Cr-Ni steels in standard supply form and after normal processing are practically unaffected by hydrogen, they can be used in difficult cases. 

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