Heat treating types

Figure 6. J-lntegral (J) vs. Change-in-Crack Length (da) Behavior for As-Received and Heat-Treated Type 21-6-9 Stainless Steels.

Besides pH, other preparative variables that can affect the microstructure of a gel, and consequendy, the properties of the dried and heat-treated product iaclude water content, solvent, precursor type and concentration, and temperature (9). Of these, water content has been studied most extensively because of its large effect on gelation and its relative ease of use as a preparative variable. In general, too Httie water (less than one mole per mole of metal alkoxide) prevents gelation and too much (more than the stoichiometric amount) leads to precipitation (3,9). Other than the amount of water used, the rate at which it is added offers another level of control over gel characteristics. 

Following wet processing, fine particle size kaolins may be calcined, ie, heat treated at about 1000°C. This treatment converts the kaolin to an amorphous pigment of significantly higher brightness and opacity (8). Properties of the various types of kaolins used in paper are shown in Table 2. 

Type II, medium-hard alloys, are harder, stronger, and have lower elongation than type I alloys. They are used for moderate stress appHcation, eg, three-quarter crowns, abutments, pontics, full crowns, and saddles. The type II gold alloys are difficult to burnish, and can usually be heat-treated. 

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-... 

The comparisons with experimental distributions would be incomplete without examining some exploding munitions data. Data of this type have been published by Mock and Holt (1983) in which explosive-filled cylinders of armco iron and several heat-treated steels were detonated, and the fragments collected and analyzed. A cumulative number distribution from one of the heat-treated steel experiments is shown in Fig. 8.33. The trend of the data in this example is typical of the six experiments performed by them. 

As with chemical etches, developing optimum conversion coatings requires assessment of the microstructure of the steel. Correlations have been found between the microstructure of the substrate material and the nature of the phosphate films formed. Aloru et al. demonstrated that the type of phosphate crystal formed varies with the orientation of the underlying steel crystal lattice [154]. Fig. 32 illustrates the different phosphate crystal morphologies that formed on two heat-treated surfaces. The fine flake structure formed on the tempered martensite surface promotes adhesion more effectively than the knobby protrusions formed on the cold-rolled steel. 

Fig. 2. (a) (b) Transmission electron microscopy (TEM) images of as-grown VGCFs (broken portion) with the PCNT core exposed field emission-type scanning electron microscopy (FE-SEM) image of (c) as-grown and (d) heat-treated VGCFs (broken portion) at 2800°C with PCNT (white line) exposed [20],... 

Materials of fabrication again vary with the nature of the gas being compressed but are usually low alloy steel, such as AISI4140 or 4340, heat treated at 1,100°F to Rockwell hardness 26 to 30, AISI Type 410 stainless steel, precipitationhardening stainless such as Armco 17-4PH or 15-5 PH, Type... 

Aluminum drillpipe is generally made of 2014 type aluminum-copper alloy. Composition of this alloy is 0.50 to 1.20% silicon, 1.00% iron maximum, 3.90 to 5.0% copper, 0.40 to 1.20% manganese, 0.25% zinc maximum and 0.05% titanium. The alloy is heat treated to T6 conditions that represent 64 ksi tensile strength, 58 Ksi yield strength, 7% elongation and a Hbn of 135- Aluminum drillpipe generally comes with steel tool joints that are threaded on to ensure maximum strength that cannot be attained with aluminum joints. 

Silent chains are similar to roller chains in that each has a master or connecting link to facilitate ease of installation and removal from a machine. They are usually made of high-carbon steel or heat-treated steel alloys. As a result, this type of chain provides trouble-free service for extended periods. 

The need for heat treatment after forming or welding is a complex topic and can only be mentioned briefly here. Generally speaking, however, unless the forming operation has been very severe it is not necessary to heat treat to restore mechanical properties of austenitic types, although in special cases it may be advisable to do so to relieve stresses. With the martensitic steels... 

Austenitic steels of the 304S15 type are normally heat treated at 1 050°C and cooled at a fairly rapid rate to remove the effects of cold or hot working, and in this state much of the carbon is in supersaturated solid solution. Reheating to temperatures below the solution treatment temperature leads to the formation of chromium-rich MjjCj precipitates predominantly at the grain boundaries with the production of chromium gradients and reduced corrosion resistance as is the case with the martensitic steels. Any attack is... 

Figure 15. Comparison of Fracture Appearance Between (a) Heat Treated (65Q°C, 24 hours) Type 21-6-9 Stainless Steel (1000 X) and. (b) Tritium-Exposed-And Aged. 627 appm helium (2000 X). Arrows Indicate Direction of Crack Propagation.

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