1st Rolling Research Articles

Effect of Rolling Temperature on the Microstructure and Mechanical Properties of Mg-2Zn-0.4Y Alloy Subjected to Large Strain Rolling

Large strain rolling (LSR) has been conducted on the Mg-2Zn-0.4Y alloy. After the 1st rolling process at 250, 300, 350, and 400 °C, the alloy demonstrates a fully recrystallized microstructure. The grain size increases from 6, 8, 12, to 17 μm with an increasing rolling temperature. After the 2nd rolling process at 300 °C, twinning and shear bands were introduced. During the 3rd rolling process at 350 °C, dynamic recrystallization (DRX) was observed and resulted in a more uniform microstructure. DRX occurred because of temperature increase and large dislocation density induced by LSR. For the room temperature tensile tests, the plates rolled at 300 and 350 °C in the 1st rolling process demonstrate higher strength and lower elongation due to twinning. The one rolled at 400 °C in the 1st rolling process, shows the most uniform rolling microstructure and the best combination of strength and elongation at room temperature.

제조 방법을 달리한 쌀가루가 설기떡의 품질에 미치는 영향

This study investigated the quality characteristics of commercial rice flour (CRF) and rice flours prepared by different milling methods for sulgidduk. For particle distribution, dried rice flour after the 1st roll mill using a pin mill showed a particle size of greater than 710 μm, whereas a particle size less than 250 μm accounted for 48% of whole rice flour. This proportion was higher than CRF after the 2nd step roll mill. Crude protein, lipid, and ash contents were significantly highest in 1st roll mill samples. For color, roll & pin made up of many small particles showed a high L value. CRF and roll & pin showed significantly higher starch damage and water-holding capacity, whereas pasting temperature, peak viscosity, and setback of RVA pasting characteristics were lower than 1st roll mill. When rice cakes were made from three kinds of rice flour, roll & pin was not significantly different compared to the CRF. However, rice cakes made with 1st roll milled rice flour showed rough crumb and crust. Rice cake made with roll & pin or CRF showed similar characteristics for texture. In the quantitative descriptive analysis, rice cake made with roll & pin showed better appearance, flavor, taste, texture, and overall acceptability than CRF and 1st roll mill. Therefore, rice flour prepared by roll & pin could be applied to sulgidduk with high quality.

Effect of Rolling Process on the Microstructure of AlMgSi Alloy

In this paper, a AlMgSi alloy for sheet materials was designed on the base of 6111 aluminum alloy, the alloy sheet was fabricated by the rolling process combination of hot and cold rolling, the effect of rolling process on the microstructure of alloy was studied. The results show that different 1st rolling pass reductions of 13%, 33% and 47%, alloy microstructure changes obviously. With the increasing of 1st rolling pass reductions, the re-crystallization structure grow in quantity, re-crystallization grain more and more dense, flat, uniform, and the second phase particles are also more small, distributes more uniform. When the first cold rolled reduction is 47%, degree of grain refinement, the second phase particles fragmentation and tissue uniformity in rolling 3st state are obviously superior to the 1st state and 2st states. The deformation inhomogeneity can be overcome by improving the first reduction rate, the re-crystallization process of synchronization between surface layer and the center layer is better.

Changes in the Composition of Raw Tea Leaves from the Korean Yabukida Plant during High‐Temperature Processing to Pan‐Fried Kamairi‐Cha Green Tea

To develop a better understanding of compositional changes occurring during the production of commercial teas, we determined by high-performance liquid chromatography (HPLC) changes in ingredient levels during each of several manufacturing steps used to produce Kamairi-cha, a premium green tea. Kamairi-cha uses pan-frying instead of the usual blanching technique to inactivate the enzymes responsible for producing traditional black tea. The resulting tea lacks the characteristic bitterness of green tea, producing a green tea that is described as sweet tasting. The processing steps used to produce this pan-fried tea were as follows: 1st roasting, 1st rolling, 2nd roasting, 2nd rolling, 1st firing, and 2nd firing. The results show that during production at temperatures up to 300 degrees C, raw leaves lost (in percent) 97.3 water, 94 two chlorophylls, 14.3 seven catechins, and 2.75 caffeine. A separate analysis showed that the final product contained 21.67 mg/g dry wt of the biologically active amino acid theanine. The results of this 1st report on changes in individual catechins and other tea ingredients in tea leaves during pan-frying make it possible to select production conditions that maximize levels of beneficial tea ingredients. The possible significance of the results for the human diet is discussed.

Experiments on the C.C.C. Single Action Tea Roller

1. The manufacturing method of black tea by the C.C.C. single action tea roller imported from Ceylon was examined with shears-plucked leaves during 1955-1957.2. The optimum feed rate of tea leaves for this roller was decided to be about 113 kg. (in the case of withering degree of 30-35%, which corresponded to 20% ess amount applied in India and Ceylon where handplucked leaves were used.3. On the above charging amount of fresh leaves, it was suitable that the revolution was 43 r. p. m. and the operation time was 40 min. for the 1st rolling, 30 min. for the 2nd.4. The most reasonable application of this roller seemed to be the combined use with the ordinary roller, it was favorable that in the 1st rolling the tea leaves were rolled by the ordinary roller and in the 2nd by the C.C.C. roller with high pressure.5. To eliminate the deterioration of the quality of tea by rising of leaf temperature during the rolling, it was necessary to putting on and taking off the weight of roller lid frequently and not to continue to press the leaves hard for long time.6. When the C.C.C. roller was used in the 1st rolling, it was recommended that the pressure of lid had to hold as light as possible and prolong the operation time 10 min. longer for each rolling process.