Temperature on Hardness

M. Tajima, T. Maki, and K. Katayama, Study of Heat Transfer Phenomena in Quenching of Steel (Effects of Boiling Heat Transfer on Cooling Curves and Water Temperature on Hardness of Steel), JSME Int. J., Series II, 33, pp. 340-348,1990,... 

In most applications WC-Co is subjected to temperatures which can be as high as 900-1000°C (as in metal cutting). Therefore knowledge of the effect of temperature on hardness is essential for a correct selection of the grades suitable for a specific application. 

Fig. 3.1-56 Effect of rolling temperature on hardness specimens quenched after hot-roUing A199.0Cu - 1100 AlMnlMg2 - 3004 AlMg2.5 - 5052 AlMg4.5 - 5082...

SP-700 Effect of aging temperature on hardness and tensile properties... 

Specimens used in tests were sections of cables with PVC outer coating. PVC was plasticized with DOF softener. The materials considered were exposed to the radiation and thermal aging. The samples have been irradiated at room temperature by hard gamma rays with 10 rad/sec dose power. A number of samples had been heated for long different times at 90°C. Besides a special specimens were cut out from outer coating for test on tensile machine like "Instron". The total doses of irradiation, times of heating and elongations at break obtained with "Instron" are listed in Table 1. 

A nonaHoyed carbon steel having 0.76% carbon, the eutectoid composition, consists of austenite above its lowest stable temperature, 727°C (the eutectoid temperature). On reasonably slow cooling from above 727°C, transformation of the austenite occurs above about 550°C to a series of parallel plates of a plus cementite known as peadite. The spacing of these plates depends on the temperature of transformation, from 1000 to 2000 nm at about 700°C and below 100 nm at 550°C. The corresponding BrineU hardnesses (BHN), which correspond approximately to tensile strengths, are about BHN... 

Nitrile rubbers, including fiber-reinforced varieties, are used both as radial shaft-seal materials and as molded packing for reciprocating shafts. They have excellent resistance to a considerable range of chemicals, with the exception of strong acids and alkalis, and are at the same time compatible with petroleum-based lubricants. Their working temperature range is from —1°C to 107°C (30°F to 225°F) continuously and up to 150°C (302°F) intermittently. When used on hard shafts with a surface finish of, at most, 0.00038 mm root mean square (RMS), they have an excellent resistance to abrasion. 

One may expect that with increasing temperature the thermal expansion in the crystalline regions will lead to an enlargement of the chain cross-section in the crystalline phase which in turn will induce a decrease in the cohesion energy of the crystals thus causing a gradually lower resistance to plastic deformation. In order to minimize the effect of the surface layer, the influence of temperature on microhardness has been investigated in PE crystallized at 260 °C under a pressure of 5 Kbar 28). The decrease of MH with temperature for the above chain extended PE material is depicted in Fig. 11. The hardness decrease follows an exponential law... 

Crystals with Frenkel or Schottky defects are reasonably ion-conducting only at rather high temperatures. On the other hand, there exist several crystals (sometimes called soft framework crystals ), which show surprisingly high ionic conductivities even at the room or slightly elevated temperatures. This effect was revealed by G. Bruni in 1913 two well known examples are Agl and Cul. For instance, the ar-modification of Agl (stable above 146°C, sometimes denoted also as y-modification ) exhibits at this temperature an Ag+ conductivity (t+ = 1) comparable to that of a 0.1m aqueous solution. (The solid-state Ag+ conductivity of a-Agl at the melting point is actually higher than that of the melt.) This unusual behaviour can hardly be explained by the above-discussed defect mechanism. It has been anticipated that the conductivity of ar-Agl and similar crystals is described... 

For covalent crystals temperature has little effect on hardness (except for the relatively small effect of decreasing the elastic shear stiffness) until the Debye temperature is reached (Gilman, 1995). Then the hardness begins to decrease exponentially (Figure 5.14). Since the Debye temperature is related to the shear stiffness (Ledbetter, 1982) this softening temperature is proportional to C44 (Feltham and Banerjee, 1992). 

Thermoplastic elastomers (TPE), 9 565-566, 24 695-720 applications for, 24 709-717 based on block copolymers, 24 697t based on graft copolymers, ionomers, and structures with core-shell morphologies, 24 699 based on hard polymer/elastomer combinations, 24 699t based on silicone rubber blends, 24 700 commercial production of, 24 705-708 economic aspects of, 24 708-709 elastomer phase in, 24 703 glass-transition and crystal melting temperatures of, 24 702t hard phase in, 24 703-704 health and safety factors related to, 24 717-718... 

Suds suppressors (LD, DW, ADW, HC) Limit suds amount when suds will interfere with cleaning Sensitivity to wash temperature, water hardness, and builder system Efficiency on the surfactant system Alkyl phosphates Silicones Soap 0-5% 0-5%... 

Other workers have studied the effects of varying current density and plating temperature on the hardness and current efficiency and have obtained similar observations (Tab. 6.6), namely that maximum current efficiency occurred at lower temperatures, higher current densities and in the absence of ultrasound (Tab. 6.6a), yet improved hardness occurred at the highest current density and in the presence of ultrasound but at lower plating temperatures (Tab. 6.6b). 

Crystal stmcture prediction by computer has made great steps forward in the last 10 years, with progress toward consistent success in blindfold tests. Fundamental uncertainties still remain, due to the unknown role of nucleation kinetics and to the neglect of temperature effects in the calculations. Success or failure still depends to some extent on hardly predictable factors and on the extent to which the experimental polymorph screening has been carried out. Presently, some of the best computational tools are not yet available to the general community of solid state scientists, being implemented in commercial, strictly copyrighted software. 

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