Hardening heat treatment

All property data for berylhum—copper are for material after age-hardening heat treatment. 

Sm-Co anisotropic powders have been developed to prepare magnets meeting high operating temperature requirements [135]. These powders are produced by pulverization of bulk ingots which have been submitted to the precipitation hardening heat treatment. 

Uses Prod, of artificial barium sulfate, other barium salts reagent (barium lake formation) lubrication oil additives boiler compounds textile dyeing pigments mfg. of white leather case hardening/heat treatment salts flux in magnesium prod. phosphoric acid purification agent... 

PH (Precipitation hardening). These are iron-chromium-nickel alloys containing precipitating element, such as Al. Strength is achieved by precipitation hardening heat treatment. One example is (17-7 PH)... 

Solid solution alloys are readily fusion welded, normally in the annealed condition. Some noteworthy examples of solid solution alloys are Ni 200, the Monel 400 series, the Inconel 600 series, the Incoloy 800 series, Hastelloys and some Nimonic alloys such as 75, and PE 13. Because the HAZ does not harden, heat treatment is not usually required after welding. Precipitation hardened alloys may be susceptible to postweld heat-treatment (PWHT) cracking. Some of these alloys are the Monel 500 series. Inconel 700 series, Incoloy 900 series, and most of the Nimonic alloys. 

The most common heat-treatable copper alloys are the beryllium coppers. They possess a remarkable combination of properties tensile strengths as high as 1400 MPa (200,000 psi), excellent electrical and corrosion properties, and wear resistance when properly lubricated they may be cast, hot worked, or cold worked. High strengths are attained by precipitation-hardening heat treatments (Section 11.9). These alloys are costly because of the beryllium additions, which range between 1.0... 

Precipitation Hardening. With the exception of ferritic steels, which can be hardened either by the martensitic transformation or by eutectoid decomposition, most heat-treatable alloys are of the precipitation-hardening type. During heat treatment of these alloys, a controlled dispersion of submicroscopic particles is formed in the microstmeture. The final properties depend on the manner in which particles are dispersed, and on particle size and stabiUty. Because precipitation-hardening alloys can retain strength at temperatures above those at which martensitic steels become unstable, these alloys become an important, in fact pre-eminent, class of high temperature materials. 

Steels iu the AISI 400 series contain a minimum of 11.5% chromium and usually not more than 2.5% of any other aHoyiag element these steels are either hardenable (martensitic) or nonhardenable, depending principally on chromium content. Whereas these steels resist oxidation up to temperatures as high as 1150°C, they are not particularly strong above 700°C. Steels iu the AISI 300 series contain a minimum of 16% chromium and 6% nickel the relative amounts of these elements are balanced to give an austenitic stmcture. These steels caimot be strengthened by heat treatment, but can be strain-hardened by cold work. 

Cladding and backing metals are purchased in the appropriately heat-treated condition because corrosion resistance is retained through bonding. It is customary to supply the composites in the as-bonded condition because hardening usually does not affect the engineering properties. Occasionally, a post-bonding heat treatment is used to achieve properties required for specific combinations. 

Because the time at high temperature is much less, austenite is produced, which is chemically inhomogeneous especially with undissolved carbides, and has a fine grain crystal size. The formation of the hard martensite requites more rapid cooling than for conventional hardening. Thus case hardening by heat treatment intrinsically requites that the surface region to be hardened be relatively thin and cooled rapidly. 

A principal commercial appHcation of the hypophosphites is ia the electroless plating (qv) process. Nickel salts are chemically reduced by hypophosphites to form a smooth adherent nickel plating to protect the iateriors of large vessels and tank cars. The coating, which can be hardened by heat treatment, usually contains 8—10 wt % phosphoms and is highly impervious. 

Table 25. Age Hardening of Aluminum Alloys 6061 and 2024 at Room Temperature after Heat Treatment and Quench...

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