Vacuum treatment, steel

Plasma created by radio wave at megahertz frequency does not require extremes of vacuum, and steel may be used in making chamber and jigs. To a certain extent the treatment remains specific to the shape, but with good electrode design it can be very effective. 

For steel when correctly hardened (typically at 800C) and tempered at 200C, a hardness of Rockwell C52-58 would be expected. Where addidonal skin hardness is needed (as on sliding surfaces of the tool) it is possible to harden by flame or vacuum treatment, but any subsequent grinding (which may be carried on final assembly of the tool) will easily remove the surface and expose the softer substrate, which will be very prone to wear. 

The VODC (Vacuum Oxygen Decarburisation Converter) operates in such a way that molten steel is contained in the converter, which is attached to vacuum pumps, steam ejectors and an argon gas source. Two distinct processes are carried out in the vacuum treatment of stainless steel to obtain a higher quality level. 

Vacuum treatment according to Figure 8.28 reduces the content of contaminants, nitrogen, oxygen and hydrogen. This gives the steel better fatigue properties. 

Figure S.2S Vacuum treatment of molten steel. (Reprinted from the booklet 5tee/with permission from Employers Association of the Swedish Steel and Metal Industry, Stockholm.)...

The aluminium left in steel after deoxidation can be removed by vacuum treatment at 1600°C (1872 K) in either a silica, magnesia, or alumina crucible, according to the following reactions ... 

A hst of polyol producers is shown in Table 6. Each producer has a varied line of PPO and EOPO copolymers for polyurethane use. Polyols are usually produced in a semibatch mode in stainless steel autoclaves using basic catalysis. Autoclaves in use range from one gallon (3.785 L) size in research faciUties to 20,000 gallon (75.7 m ) commercial vessels. In semibatch operation, starter and catalyst are charged to the reactor and the water formed is removed under vacuum. Sometimes an intermediate is made and stored because a 30—100 dilution of starter with PO would require an extraordinary reactor to provide adequate stirring. PO and/or EO are added continuously until the desired OH No. is reached the reaction is stopped and the catalyst is removed. A uniform addition rate and temperature profile is required to keep unsaturation the same from batch to batch. The KOH catalyst can be removed by absorbent treatment (140), extraction into water (141), neutralization and/or crystallization of the salt (142—147), and ion exchange (148—150). 

Ladle metallurgy, the treatment of Hquid steel in the ladle, is a field in which several new processes, or new combinations of old processes, continue to be developed (19,20). The objectives often include one or more of the following on a given heat more efficient methods for alloy additions and control of final chemistry improved temperature and composition homogenisation inclusion flotation desulfurization and dephosphorization sulfide and oxide shape control and vacuum degassing, especially for hydrogen and carbon monoxide to make interstitial-free (IF) steels. Electric arcs are normally used to raise the temperature of the Hquid metal (ladle arc furnace). 

Vacuum Processes. More complete control over ladle treatment is achieved by the abiHty to seal a vessel weU enough so that a good vacuum can exist over the steel. Although the expense can be justified for steels with the most difficult property requirements, for many purposes less elaborate treatments are adequate. Many possible configurations exist (21). 

The optical properties of electrodeposited, polycrystalline CdTe have been found to be similar to those of single-crystal CdTe [257]. In 1982, Fulop et al. [258] reported the development of metal junction solar cells of high efficiency using thin film (4 p,m) n-type CdTe as absorber, electrodeposited from a typical acidic aqueous solution on metallic substrate (Cu, steel, Ni) and annealed in air at 300 °C. The cells were constructed using a Schottky barrier rectifying junction at the front surface (vacuum-deposited Au, Ni) and a (electrodeposited) Cd ohmic contact at the back. Passivation of the top surface (treatment with KOH and hydrazine) was seen to improve the photovoltaic properties of the rectifying junction. The best fabricated cell comprised an efficiency of 8.6% (AMI), open-circuit voltage of 0.723 V, short-circuit current of 18.7 mA cm, and a fill factor of 0.64. 

Thermal conduction (also referred to as electrical conductive heating or in situ thermal desorption) supplies heat to the soil through steel wells or with a blanket that covers the ground surface. As the polluted area is heated, the contaminants are destroyed or evaporated. Steel wells are used when the polluted soil is deep. The blanket is used where the polluted soil is shallow. Typically, a carrier gas or vacuum system transports the volatilized water and organics to a treatment system. 

According to the vendor, the capital costs for the treatment system include a 200-actual cubic-feet-per-minute (ACFM) vacuum pump, two transfer pumps, a carbon steel knockout pot, and associated instrumentation and piping. Operation and maintenance costs for the system include estimates for additional granular activated carbon (GAC) units, liquid- and vapor-phase analysis, weekly monitoring, electricity, and routine maintenance. These costs vary, depending on the monitoring requirements, contaminant concentrations, and other variables (D13124Y, p. 492). 

Coupons of Type 304 stainless steel were prepared by mechanical abrasion and rinsed with methanol. Each sample was analyzed by XPS prior to treatment to ensure that no detectable casually-introduced chlorine was present. Two separate series of laboratory experiments were done one series (a) followed the effects of short-term contact between chlorocarbon and the alloy surface, a second series (b) investigated the effects of prolonged vapor and liquid contact with the alloy in a glass refluxer. In series (a) the clean alloy surface was swabbed using trichloroethane-soaked tissue and immediately inserted into the vacuum chamber of an XPS spectrometer for analysis. After analysis, the same coupon was exposed to the atmosphere for periods of 72 and 336 hours... 

For plasma induced by a high-frequency microwave system, extremes of vacuum are not needed, but particular care in the design of the system is essential in ensuring even treatment. Since microwave energy is employed, the use of steel for chamber and jigs is precluded. 

This scrap metal includes metal munitions casings after the chemical agent has been drained and the casings have been treated in the MPF. Drained bulk containers and metal munition casings and components are treated in the MPF to destroy agent residues. After treatment in the MPF, the metal parts are allowed to cool, vacuumed to remove loose paint flakes and ash residue, and stored temporarily in roll-off bins prior to shipment off-site. Munition bodies and empty TCs are carbon steel and may be recycled by smelting at either a commercial recycling facility or the Rock Island Arsenal,6 or disposed of at a hazardous waste landfill. 

The violet form can also be obtained from some preparations of red phosphorus by the following treatment. The finest particles are washed away in a stream of water until only dark steel-blue particles are left these are boiled with 30 per cent, sodium hydroxide solution, washed again, boiled with 5 per cent, nitric acid, washed with hot and cold water, then with absolute alcohol and ether, and allowed to stand until dry in a vacuum desiccator with concentrated sulphuric acid.2 The density of this preparation is about 2-2 (2T8 to 2-23). 

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