Forgings, material requirements

Explosively forged materials manufd at National Northern exhibited physical properties above minimum conventional requirements and are considered of good quality (Ref 7, p 5)... 

Silica melts at 1710°. Even when slowly cooled the molten material sets to a vitreous, non-crystalline solid. Its plastic range allows masses to be forged and hollow ware to be blown its low coefficient of expansion renders it immune to thermal shock its transparency especially to u.v. makes it suitable for lenses and prisms. Specially pure synthetic silica is now made for laboratory ware used in preparing the pure materials required by the electrical industry (e.g. transistors), and for optical parts calling for minimum absorption. 

Deeper die cavities require more draft than shallow cavities. Draft angles for hard-to-forge materials, such as titanium and nickel-base alloys, should be larger than when forging easy-to-forge materials. 

Niobium and Tantalum Alloys. Contrary to Mo and W, pure Nb and Ta are deformed at room temperature. Only highly-alloyed materials require breaking down the ingot microstructure either by forging or extrusion at elevated temperatures. In these cases... 

When material requires straightening, the work should be done by pressing or another non-injurious method prior to any layout or shaping. Heating or hammering is not permissible unless the material is heated to a forging temperature. 

What material was required in the forms of plate, forgings, or castings to conduct the repair ... 

While evaluating the mechanical properties of materials, attention must also be given to availability. Sometimes an alloy of attractive properties is not commercially available. It may be possible to obtain special heats for large parts such as appreciable quantities of plate, large forgings, and so forth, but it may be difficult to contain smaller quantities required for incidental pieces. 

Material of construction for hold-down (flange, screwed) arrangement. Usually forged carbon steel is satisfactory, although aluminum or other material may be required to match vessel and/or atmosphere surrounding the disk assembly. 

Materials of construction depend on the metallurgical requirements and pressure of the gas being compressed hut usually the more popular materials include cast iron, cast steel, alloy steel, or forged steel (high pressure). Figure 12-42 illustrates the extent of damage internally when materials of construction are not resistant to possible effects of internal corrosion. 

Unalloyed molybdenum is available commercially in almost all forms, from forging billets and plate to seamless tubing, foil and wire. In addition, the following molybdenum-base alloys can be considered as established engineering materials Mo-0-5Ti-0-8Zr (designated TZM) and Mo-30W. A Mo-30Ta alloy has also been produced for specific applications where high corrosion resistance is required. 

If specified, the vendor shall furnish material certificates that include chemical analysis and mechanical properties for the heats from which the material is supplied for pressure-containing castings and forgings, impellers and shafts. Unless otherwise specified, piping nipples, auxiliary piping components, and bolting are excluded from this requirement. 

The methods for forging, welding, compaction and conditioning require preparation of the metal and die surfaces prior to the operation. Each of these operations requires higher prrssure forces than those needed for expl forming of sheet material. 

Obviously, one requirement for an adhesive is that it flow easily to cover a surface. This is a more complex business than it first appears. One might naively think that the governing feature is whether we are dealing with a thin or a thick liquid, but this is not the case. If we put a drop of oil in an iron skillet, it spreads, but on a Teflon surface it beads up. The explanation revolves around surface energies, which are a measure of the relative strengths with which atoms on the surface of a material are attracted to atoms inside the bulk of the material. In a sense, this determines how much attraction these surface atoms can spare for other substances. In the case of Teflon, very little. Teflon is composed of long chains of carbon atoms, with each carbon also joined to two fluorine atoms. The fluorines, which stick out from the carbon skeleton, represent the exposed part of the molecules, the part that could potentially interact with other molecules. Fluorine, once it has bonded to carbon, is notoriously unreactive, and it is not interested in forging other... 

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