Jominy hardenability tests have been performed in steel metallurgy for many years. The relationship between cooling rate, and thickness for A356 aluminum quenched in water and a polymer quenchant, Heat transfer rates decrease as the thickness of the polymer ¢lm increases, and, the polymer ¢lm thickness is dependent on both agitation and quenchant con-. A Type K, thermocouple was inserted to the geometric center of the bar. cold water, hot water and a 20% solution of a Type 1 quenchant. A simple analysis is often suf¢cient to assure that, reasonable £uid £ow around the part is obtained. Torgerson and Kropp conducted residual stress and other mechanical property, measurements on specimens quenched in hot water and a Type I polymer quenchant, at various concentrations using both AA7050-T736 forgings and plate [92]. ), The properties of aluminum alloys are dependent on the amount of alloy precipi-, tation that occurs during cooling. In such cases, an aqueous poly(alkylene glycol)-PAG copolymer solution may be used. Technology’’, Hrterei-Tech. These quenchants, Quench hardenable aluminum alloys are typically quenched in cold water. Immersion rates are usually in, the part in a way that promotes £uid £ow around the surface. ), actors at 99.5% of Attainable Yield Strength, C, quenched and overaged to obtain exfolia, C-Curves for (A) 2017 (B) 7075 (C) 6061 and (D) 6063. Water’’, Heat Treating, May 1989, pp. If so, the delta value, after being reasonably stable. Ways of Determining the Effects of Convection’’, Eingereicht bei Materials Science. Statistical models for quench factor and predicted, yield strength were developed using standard multiple linear regression analysis, techniques to determine the signi¢cant variables relative to the modeled response, cross-section size for (a) 6061; (b) 2024-T3 and T-4; and (c) 7, The contour plot shown in Fig. The objective of the solution process is to maximize, the concentration of hardening elements including copper, zinc, magnesium, and (or), silicon in the solid solution. 7075 aluminum plate as a function of water temperature. capable of producing acceptable properties in the section thicknesses of interest, and (b) quenched in 25% Type I quenchant on its side to facilitate more uniform £uid £ow to, as previously discussed. Usually, this is accompanied by cooling rate, not surprisingly, may cause corrosion. PAG copolymer used to formulate the quenchant. This means that, the quenching behavior determined in water with silver probes can be compared with, those obtained for aluminum probes. In either case, the presence of salt may produce, higher cooling rates (see Table 16) and increase the separation temperature of the, PAG copolymer in the Type I quenchants [68]. the ‘‘oil-can’’ effect. endstream endobj startxref Liquid Metals, Cryogens, Hydrocarbons and Water’’, J. Grain boundary corrosion may also occur when the grain boundary, precipitates are either more anodic than the adjacent solid solution (Mg, The degree of intergranular corrosion may be controlled by selection of the, temper and maximizing the cooling rate per, trol. Thick parts of high–strength aluminium alloys usually undergo a drastic quench which gives rise to thermal stresses and may cause distortion of products. Aluminum Alloys’’, Heat Treating, 1983, 15(3), pp. and polymer concentration, bath agitation is also an important variable [27,28]. Vyssh. Die Zuverlässigkeit des Verfahrens wurde anhand von Kontrollrechnungen (explizites Differenzenverfahren nach Binder-Schmidt) nachgewiesen. 1. Similar problems may occur if aluminum is joined, to copper, such as can occur when copper wire is used to fasten aluminum parts. index is affected by oil and metallic salts. involved in quenching is critically important, especially with water quenching. 348^354. control the effect of water vapor [75,76]. %%EOF is preferred because it is odorless, rela-. The authors studied the use of new aqueous solutions to achieve the optimal accelerated cooling in tempering of the high strength aluminum alloys. The higher hardness is a result of more solute elements being kept in solution at high, Although little variation in Vickers hardness is observed after furnace cooling, and then tempering to the T6 condition, the ¢nal hardness does increase with quench, cooling rate. Heat Mass Transfer, 1971. This. 31. The selection of the polymer concentration for speci¢c aluminum alloys is section, size dependent. 15 [7], and the conclusions drawn from this study are summarized as follows: either the T4 or T6 conditions for AA2024. during nucleate boiling, and the heat transfer coef¢cient, below the boiling point of the quenchant, the rate is again reduced during the con-, Since aluminum solution heat treatment temperatures are signi¢cantly higher, than the Leidenfrost temperature, ¢lm boiling is to be expected initially when, quenching into water [45,46]. ess’’, Hrterei-Tech. The concentrated solution, which does not pass through the membrane is either recycled through the membrane. But, if the cooling rate is too fast, there may be an increased tendency. Forty-¢ve tensile specimens were removed, from ¢ve lots of bar extrusions ranging in diameter from 12.7, in water ranging in temperature between 25, media, including a polymer quenchant, fast oil, and a £uidized bed were also, The standard deviation in yield strength about the regression line was 2.1 MPa, part can be predicted rather accurately if the, quenched is known and if a valid cooling curve is available. The results of this study are shown, in Table 7 [10]. Ductility Potential and Quality Index Development, Quenching aluminum parts in water: Problems and alternatives, TYPE I POLYMER QUENCHANT ALTERNATIVES TO WATER: A REVIEW, Quench Sensitivity of an Al7 Pct Si0.6 Pct Mg Alloy: Characterization and Modeling. When this occurs, racking con¢guration may be used to help, lower propensity for distortion, proper racking procedure cannot be, ignored. Cross-section of surface blistering (as polished, 50, Galvanic corrosion is caused by the contact of dissimi-, (warm water cooling time). medium approximates that of cold water (if cold water is used). Tensile Properties and Minimize Distortion in Aluminum^Alloy Parts’’, Heat Treat. (This is why ‘‘hot’’, There is a cooling rate ‘‘window’’ that must be identi¢ed to obtain both optimal, physical properties and minimum residual stress and distortion. Sectioning showed that the blisters and voids were present, Schuler reported that such blisters were due to high temperature oxidation of, the residual hydrocarbon material during solution heat treating which produced. These physical properties are speci-. Although the overall. 54 [51]. no signi¢cant effect on quench factor under these experimental conditions. A volatile £uoride atmosphere, such as that produced by. This can be determined by locating the upper-limit, ordinate of Fig. Mat. the metal, i.e. These data show that time step changes in the range of 0.1^0.4, caused no appreciable change in the calculated quench factor. 63. Thermal stress due to high thermal gradients may be reduced by, raising the water temperature as illustrated in Fig. article. The depth of, attack was consistently higher toward the center of quenched bars when the cooling, Type I polymer quenchants have been reported to offer signi¢cantly greater residual, stress reduction than hot water in a number of studies. decreased as the ¢lm coef¢cient decreased. A cooling technique able to provide precisely controlled high cooling speeds is described. The effect of water, temperature and polymer concentration on cooling time has been compared and, some results are illustrated in Fig. Alloy AA2024-T6 was slightly superior to AA2024. This is usually expressed as volume/min at 25. rate of the feed stream of the incoming quenchant, In membrane separation technology, the recovery rate is used to characterize. The furnace system utilized for the aluminum sheet distortion is illustrated in Fig. The coef¢cients, describing the C-curve for 7075-T73 are given in Table 6. h��Zmo�8������w However, cold water, hot water and aqueous polymer solutions, are the most frequently used throughout the world to process aerospace aluminum, If the diffusion process is suf¢ciently fast during quenching, alloying elements and, compounds may precipitate in the grain boundaries. ), 1984, ASM International, Materials Park, OH, pp. 80^82. (37.6 mm) diameter round bars of 7075-T73 aluminum. tortion in aluminum, excessive distortion still sometimes occurs. An aluminum alloy containing 4% copper in solid solution will exhibit, boundaries may reduce the electrochemical potential to -0.84, anodic. for aqueous polymer quenchants as for water. The electrochemical potential of various aluminum alloys, provided in Table 19, shows that the presence of copper in solid solution with aluminum makes it more, cathodic [88]. Other factors include transfer rate from the furnace, to the quench, air entrainment in the quench tank, and the ratio of section, mass/surface area [90]. Synthetic quenchants were developed to achieve greater control over quenching speeds, to improve heat transfer characteristics, and to reduce pollution and fire hazards.