Flat Ingots Research Articles

Method for evaluating the change in specific volume of refratory substances during crystallization

A method is proposed for quantitative evaluation of the change in specific volume of refractory substance during a liquid-solid phase transition according to the surface shape of a flat ingot crystallized under conditions of central symmetrical heating. The accuracy of the estimate is up to 5–8%. With certain limitations the method is applied to a quantitative estimate of the volumetric effect of crystallization and in a number of cases melt density of the refractory materials themselves, for which obtaining information about melt density by any other method is impossible. Using the proposed method an estimate is provided for the density of molten yttrium and erbium oxides close to the melting temperature (for Y2O3 T m = 2440°C, for Er2O3 T m = 2430°C respectively).

Growth texture due to directed crystallization of high-temperature nickel alloys

Processes of formation of growth texture [001] due to directed crystallization of high-temperature nickel alloys are considered and their qualitative and quantitative characteristics determined. Simulation of competitive growth is performed for flat bicrystal ingots.

Influence of Ni concentration and Ni3Sn4 nanoparticles on morphology of Sn-Ag-Ni solders by mechanical alloying

The mechanical alloying (MA) process was employed as an alternative method to produce the lead-free solder pastes of Sn-3.5Ag-xNi (x=0.1, 0.5, 1.0, 1.5, and 2.0) in this study. When the Ni concentration was low (x=0.1, 0.5), MA particles agglomerated to a flat ingot with particle sizes >100 µm. For higher Ni concentration (x=1.0, 1.5, and 2.0), MA particles turned into fragments with particle sizes <100 µm. The particle size of the solders appeared to be dependent on the Ni concentration. To reduce the particle size of SnAgNi alloys with low Ni concentration, Ni3Sn4 nanoparticles were doped into Sn and Ag powders to derive a Ni3Sn4-doped solder. For the Ni3Sn4-doped solder, the particle size was smaller than that doped by the pure Ni. The distinction of milling mechanism between Ni3Sn4-doped solder and the pure Ni-doped solder by MA process was probed and discussed. In addition, differential scanning calorimetry (DSC) results ensured its feasibility in applying the solder material in the reflow process. Wettability tests between solders and Cu substrate also revealed that the wetting angles for Ni3Sn4-doped solder with low Ni concentration (0.1 and 0.5 wt.%) were smaller than those for pure Ni-doped solder. The wetting angles on both Cu substrate and electroplated Ni metallization for SnAgNi solders were also comparable with commercial Sn-3.5Ag and Sn-3.0Ag-0.5Cu solders. Favorable wettability of the as-derived solder in this study was clearly demonstrated.

Effect of Admixtures of Iron and Silicon on the Structure and Cracking of Near-Edge Volumes in Rolling of Large Flat Ingots from Alloy 7075

The effect of the content of iron and silicon admixtures in aluminum alloy 7075 on the composition, morphology, and fineness of phase components in the microstructure of ingots with cross section of 390 – 1330 mm in homogenized condition is studied. The mechanical properties of ingots at room and enhanced temperatures are determined depending on the content of iron and silicon in the alloy. The effect of the iron and silicon content in alloy 7075 on fracture of near-edge volumes in the process of hot rolling of plates with a thickness of 76.3 – 152 mm is determined.

Analysis of temperature state of massive flat ingot in conditions of radiational contraflow

Analysis of temperature state of massive flat ingot in conditions of radiational contraflow

New method of hot rolling for fabricating anisotropic Pr-Fe-B-based magnets

A unique method of hot rolling is described which fabricates high performance plate-shaped magnets from a cast Pr17Fe76.5B5Cu1.5 alloy. A flat ingot of the alloy with fine-scale columnar grains of a Pr2Fe14B phase is prepared by chill casting. The ingot is hot rolled in such a way that the roll pressure is applied perpendicular to the preferential growth direction of the columnar grains. A maximum energy product of 25.3 MG Oe has been obtained by this method.

Improving the quality of continuous-cast slabs by using molds with heightwise-varying conicity

The mechanism responsible for this type of crack was discovered in studies of the thermal and stress--strain state of a flat ingot 150 x I000 mm in cross section in the mold of a continuous caster. The studies were based on the use of a certain mathematical model [0. V. Martynov, S. V. Khokhlov, and A. M. Kondratyuk, "Mathematical modeling of the thermal and stress-strain state of a continuous-cast ingot solidified in the mold zone," in: Mathematical Modeling of Metal and Alloy Solidification Processes [in Russian], Novosibirsk (1983), pp. 76-77], It was established that a gas gap is formed under the surface of the liquid metal near the ingot-mold boundary. The skin of the ingot bends here under the pressure of the molten metal, and there is sharp reduction of heat removal from the ingot. This in turn lowers the rate of increase in the thickness and strength properties of the skin and rapidly lowers the temperature in the inside layers of the skin relative to its external layers.

Effect of sulfur on the properties of copper

However, with an increase in sulfur content from 0 to 0.5% the mechanical properties of copper are almost unchanged, even such asensitive property as necking [6], and only with an increase in sulfur content in copper to 1% are they reduced. It was shown in [7] that with a content of 2-3% S (by weight) copper in fact becomes brittle. The widespread opinion in recent years that sulfur in small amounts causes copper embrittlement is based on the fact that sulfur was detected at the fracture surface of specimens on whose tensile curves there was a drop in ductility. On the basis of this it was concluded that embrittlement of copper is caused by sulfur impurity located at grain boundaries [8]. It was established in [2] that with a content of less than 0.0018% S in copper, in order to avoid cracking it is necessary to carry out prolonged annealing so that sulfur is transferred into solid solution. Sulfur in copper is in the form of copper sulfide Cu2S globules [9]. It is also well known that sulfur is added to copper in an amount up to 0.03% in order to improve cuttability. In view of this contradictory data it is of interest to study the effect of sulfur on the properties of copper. The effect of sulfur on the mechanical properties of copper M1 and MIR was determined. For this purpose sulfur was added to molten copper MOO in different forms; pure sulfur, copper sulfate containing water, and anhydrous copper sulfate (after roasting). Roasting of copper sulfate was carried out at 140°C for 20-30 h in order to obtain almost constant weight. Anhydrous copper sulfate, which is white in color, rapidly absorbs water, and therefore melting was carried out on the same day when the weight of copper sulfate became almost constant. Copper sulfate was charged in amounts corresponding to the sulfur content in copper (0.030.04%). Melting was carried out under a layer of carbon with deoxidation by phosphorus and ~ without it. A copper--phosphorus master alloy (9% P) was used for deoxidation, calculated on the basis of 0.04% P in copper. Metal pouring was carried out into a horizontal copper mold. In those cases when sulfur (in any form) was added to copper without phosphorus, during solidification swelling of the ingot was observed with an increase in its volume by about a factor of two. Ingots were machined on all sides for complete removal of the rough surface. In order to obtain circular blanks 80 mm in diameter for pressing they were cut from the flat ingots.

大型扁平鋼塊の内質におよぼす鋼塊形状の影響

Influence of shape, dimensions, and hot-topping conditions of 23 to 90 ton large flat ingots on the occurrence of heterogeneities such as channel-type and centerline segregations and centerline loose structure has been made clear to optimize the design of HSLA steel ingots for extra-heavy plates.Critical values of local solidification rate and local cooling rate for the formation of the channel-type segregation have been evaluated with the aid of heat-transfer calculation on these ingots. A speculative model for the later stage of solidification has also been presented which gives reasonable interpretation of the formation of the centerline heterogeneities characteristic in these large flat ingots.