Annealing and Tempering

The upper use temperature for annealed ware is below the temperature at which the glass begins to soften and flow (about Pa-s or 10 P). The maximum use temperature of tempered ware is even lower, because of the phenomenon of stress release through viscous flow. Glass used to its extreme limit is vulnerable to thermal shock, and tests should be made before adapting final designs to any use. Table 4 Hsts the normal and extreme temperature limits for annealed and tempered glass. These data ate approximate and assume that the product is not subject to stresses from thermal shock. 

In a series of tests using annealed and tempered flat plate, SSV has discovered that the surface compression resists penetration of particle impact when subjected to a controlled sand abrasion environment. ... 

For steels that are most frequently used in the annealed or normalised condition the most important structural parameter that can be influenced by heat treatment is the grain size, although the extensive use of welding as a means of fabricating mild steels means that martensitic and tempered martensitic... 

Many users have reported satisfactory performance of annealed or normalized and tempered steels produced before 1969, as shown in Figure 1. These steels have been used for pressure-retaining equipment at design stress levels allowed by the 1969 or earlier editions of commonly-accepted codes (such codes include the ASME Code, Section Vlli, Division 1 the standards of the American National Standards Institute and, for the lower-strength materials, those of Deutsche Industrie-Normen). However, pressure vessels in hydrogen service have also been constructed using the higher allowable stresses permitted in either Section VHI, Division 2, or modifications of Section III of the ASME Code. Quenched and tempered or normalized and tempered steels have normally... 

Stress values shown are for materials in the normalized and tempered condition, or when the heat treatment is unknown. If material is annealed, use the following value above 950°F at 1,000°F, 8.0 ksi. 

Chromium is the most effective addition to improve the resistance of steels to corrosion and oxidation ar elevated temperatures, and Ihe chromium—molybdenum steels are an important class of alloys for use in steam power plants, petroleum refineries, and chemical-process equipment. The chromium content in these steels varies from 0.5 to Ill s. As a group, the low carbon chromium—molybdenum steels huve similar creep—rupture strengths, regardless of the chromium content, hut corrosion and oxidation resistance increase progressively vvith chromium content. Most of the chromium — molybdenum steels are used in the annealed or in the normalised and tempered condition some ol the modified grades have better properties in the quench and tempered condition. 

The hot strip is pickled and passed through cold and temper nulls, alter which it i passed through annealing and tinning lines. Further, zinc, tcrnc. aluminum, or plastic coaling can he applied for additional corrosion resistance. 

Heat treatment processes consist of annealing, quenching and tempering, precipitation hardening and case hardening. 

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