ISSN 0412-1961
CN 21-1139/TG
Started in 1956

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    AN INVESTIGATION OF INTERNAL DEFECTS IN HIGH-CHROMIUM STAINLESS STEEL
    LEE HSUN;HO CHAIN-CHU;CHANG CHIN-FANG;FUNG MUN-CHU;YAN SHO;CHAO HWEI-TIEN Institute of Metal Research; Academia Sinica
    Acta Metall Sin, 1957, 2 (1): 1-18. 
    Abstract   PDF (10707KB) ( 605 )
    In the manufacture of stainless steel of the high chromium type, axialcracking or porosity in ingots and ghost lines in forged billets were frequentlyencountered. It is shown that these two kinds of defects are of the same origin, billets made from ingots free from axial cracking were also immune from ghostlines. The formation of axial cracking in ingots occurs during solidification, there-fore cooling conditions which affect the interval of solidification must play animportant role in assessing the extent of cracking. The use of refractory ingot-mould led to complete immunization of axial cracking, whereas the adoption ofother alternative means such as increasing the tapering of the ingot or decreasingthe wall thickness of the ingot-mould was not so effective. To certain extents axial cracking in ingots or ghost lines in billets wereassociated with the presence of nonmetallic inclusions in steel. Through an im-provement of deoxidation procedure during smelting, the nature and the distri-bution of inclusions were favourably changed. This, supplemented by the adoptionof thin-walled ingot-mould, has been tried in works practice, the severity of axialcracking in ingots or ghost lines in billets being greatly lessened. It is consideredthat the fluidity and surface tension of liquid steel may vary with the amount,the nature and the shape of inclusions present, any change in the latter whichwill lead to an improvement of the filling properties of the liquid steel must havea favourable influence towards the immunization of solidification defects. Smelting and casting in vacuum below certain pressure range resulted in per-fectly sound ingots, such ingots showed an external zone of columnar crystalsmuch smaller than those smelted and cast under similar conditions but in air.There may be many reasons for the above observation, for example, vacuum pro-motes degasification, the transfer of heat between ingot and mould is altered byvacuum, the properties of the liquid steel in vacuum and in air are different, etc.Some of these problems undoubtedly deserve further investigation. In the mean-time, it can be said that vacuum smelting and casting appear to be the bestmethod to ensure the production of high quality stainless steel.
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    AN INVESTIGATION OF CHEMICAL EQUILIBRIA IN THE BLAST-FURNACE HEARTH Ⅱ. THE SILICON-SULFUR, SILICON-CARBON AND SILICONMANGANESE EQUILIBRIA
    CHOU YUAN-HSI Institute of Metallurgy and Ceramics; Academia Sinica
    Acta Metall Sin, 1957, 2 (1): 19-30. 
    Abstract   PDF (850KB) ( 492 )
    In a previous paper, it has been found that the manganese-sulfur equilibriumis approached in the blast-furnace hearth in agreement with the conelusions of somerecent publications. This paper presents an analysis of the same data used in theprevious paper with a view to investigating the equilibria batween silicon and theother components dissolved in liquid iron sach as salfur, carbon and manganese. It is shown that neither the silicon-sulfur nor the silicon-manganese equilibriumis approached in the blast-furnace hearth, although a parellel relationship existsbetween [%S]~(1/2)/(α_(SiO_2))~(1/2) and (%S)/[%S] and also between [%Si]~(1/2)/(α_(SiO_2))~(1/2)and [%Mn]/(%MnO). By using [%Si]~(1/2)/(α_(SiO_2))~(1/2) as an index ot the degree of silicon reduction,it has been found that an increase in slag basicity promotes silicon reduction in theblast-furnace hearth. Consequently, it is possible for the silicon-carbon reaction toapproach equilibrium in the blast-furnace hearth provided that basicity is highenough. The favorable effect of increasing basicity on the degree of silicon reduc-tion is briefly discussed from the view point of the mechanism of reduction.
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    ON THE CONCENTRATION OF CADMIUM AND RECOVERY OF LEAD FROM THE LEAD BLAST FURNACE DUST
    CHAO PEI-YING;LEE KENG-SHENG;FANG BING;TAN KWO YONG;WANG CHUEN-CHI Institute of Metal Research; Academia Sinica Smelting Works No. l; Ministry of Metal Industries
    Acta Metall Sin, 1957, 2 (1): 31-40. 
    Abstract   PDF (870KB) ( 438 )
    On the basis of the distribution of lead, cadmium, arsenic and zinc amongthe various phases during the smelting process, the disadvantages of the currentlyadopted method using silica as slag-forming material for the treatment of leadblast furnace dust have been discussed. Experiments have been carried out in treating the dust with a new method,which is based upon the iron precipitation reaction with Na_2CO_3 as flux. Resultsobtained show: 1) 99.55% cadmium of the original dust may be concentrated intothe secondary dust; 2) 95.6% of lead may be recovered simultaneously, its purityis about 97%; 3) as cadmium in the secondary dust is easily leachable, a rate ofrecovery of cadmium as high as 98.5% could be obtained. It is suggested that,the present method, in view of its high recovery of valuable metals and its com-paratively simple operating procedure, is well suitable for the dust treatment inthe lead smelting industries.
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    THE PROPERTIES OF NICHROME 80 Ni-20Cr UNDER MECHANICAL WORKING
    CHANG TSO-MEI;MAN SHOO-SHAN;GAU TZE-MING Institute of Metal Research; Academia Sinica
    Acta Metall Sin, 1957, 2 (1): 41-63. 
    Abstract   PDF (5678KB) ( 545 )
    In order to find out the properties of Nichrome 80 Ni-20 Cr under mechanicalworking, a systematic research has been conducted on the workability, forging, roll-ing, wire-drawing and heat-treatment of this material. Wires of 1 mm diameterhave also been successfully drawn from rolled rod that has been made from ingotsunder laboratory conditions. These have been tested for life in accelerated lifetest apparatus of our own make and have been found to possess satisfactory pro-perties as a heating element. The following are the chief results obtained: 1. From the results of the various workability tests and also results from forg- ing and rolling tests, this alloy has best hot-working properties within the tem-peratures of 1100℃ and 1300℃, Between 800℃ and 1000℃, there exists a brittletemperature range. It is best to avoid this brittle temperature range duringmechanical working. 2. The resistance to deformation of this material lowers gradually with therise in temperature. Even at the high temperatures of 1000—1300℃, there ismarked increase in resistance to deformation with the increase in reduction byrolling. When flat specimens are rolled, linear relationship exists between reduc-tion and the resistance to deformation between temperatures of 800℃ and 1300℃.The lateral spread also increases rapidly with the increase in reduction by rolling.When the reduction is below 30%, a rise in temperature increases the value oflateral spread. 3. With a view to obtaining products of good quality, the anvils of hammersused should have well-rounded edges in order to avoid the occurrence of folds.Similarly, in roll pass designs, the lateral spread should be carefully consideredin order to eliminate the occurrence of ears and consequently the folds producedfrom it. The drawing dies should have smooth working surfaces and the lubricantused should be clean. 4. According to the degree of cold work, the best results could be obtainedin heat-treating this material within the temperatures of 900℃ and 1050℃ whenthe soaking time is kept between 20 to 30 minutes. 5. The well-treated alloys have good cold-drawing properties. During experi-ments, the greatest reduction per pass permissible for a single drawing operationreached 35.4%; while in successive drawing, as much as 90%, reduction in cross-sectional area was recorded.
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    THE EFFECT OF BORON ON THE NUCLEATION AND GROWTH OF PEARLITE
    LEE LING;CHI MIN-WEI;CHUNG CHING-CHI;MEO YONG-TZE Institute of Metallurgy and Ceramics; Academia Sinica Nanking Unioersity; Department of Pkysics
    Acta Metall Sin, 1957, 2 (1): 65-74. 
    Abstract   PDF (756KB) ( 606 )
    It was found in this investigation that boron exerted considerable influenceon the nucleation and growth of pearlite. In a hypoeutectoid steel, boron delayedthe starting time of pearlite formation at the maximum pearlite formation temp-erature. Boron did not effect the relation of nucleation rate with time butonly increased the incubation period for pearlite nucleation. In the eutectoidsteel, boron similarily delayed the starting time for the maximum pearlite formationtemperature, but did not effect the nucleation rate with time. It was postulatedthat the austenite grain boundary energy was probably lowered by boron atomsand that there were not enough energy for the formation of pearlite nucleusand thus increased the austenite stability. It was found by experiments thatboron increased the growth rate of pearlite, both in hypoeutectoid and eutectoidsteels. The authors proposed that within the temperatures range of pearlite formation,the reason why boron delayed the beginning of austenite transformation and notthe end of transformation was due to the increased rate of pearlite growth.
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    THE EFFECT OF BORON AS A FUNCTION OF AUSTENITISING TEMPERATURE
    LEE LING;YU SHOU-LU;CHEN CHUNG-LIAN Institute of Metallurgy and Ceramics; Academia Sinica Chao Tung University; Department of Mechanical Engineering
    Acta Metall Sin, 1957, 2 (1): 75-88. 
    Abstract   PDF (3973KB) ( 609 )
    The influence of austenitising temperature upon hardenability was determinedfor two boron-treated steels; and it was shown that under different conditions ofheat treatment, the hardenability of boron steel decreases with increasing tempera-ture. The presence of oxygen and nitrogen has an appreciable effect in decreasingthe hardenability of boron steels, but the distribution of free boron atoms in aus-tenite has a more profound effect on hardenability. Investigations on the formation of boron constituent in boronised specimensshowed that by direct quenching from high austenitising temperatures, the boronprecipitate was distributed uniformly both at the austenite grain boundaries andwithin the grains. While in the isothermally treated, normalised, or slowly cooledspecimens, the boron constituent mainly ptecipitated at the austenite grain boundaries.Thus it was proposed that the loss of hardenablility of boron steels at high auste-nitising temperatures was probably due to the desorption of boron atoms from thevicinity of the austenite grain boundaries; consequently there will not be enoughboron atoms to lower the grain boundary energy and the boron hardenabilityeffect was temperarily lost.
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    THE FORMATION OF CHI PHASE IN A Mo-BEARING STAINLESS STEEL
    CHUANG YU-CHIH;LIU CHIA-LO;CHANG CHING-CHUNG Institute of Metal Research Academia Sinica
    Acta Metall Sin, 1957, 2 (1): 89-105. 
    Abstract   PDF (10161KB) ( 665 )
    The decompsition of δ-ferrite in the temperature range 550°—1000℃ inquenched 17/5/6 Cr-Ni-Mo Stainless steel specimens has been studied by meansof microscopic and X-ray diffraction method. It is shown that the nature of thedecomposition product of δ-ferrite varies with the reheating temperature, Chi andaustenite appeared in the temperature range 700—1000℃, Whereas below 700℃Fe_3Mo_3C and (Cr, Fe, Mo)_23C_6 were formed from δ-ferrite instead of Chi. The morphology and mechanism of Chi formation are also dependent on thereheating temperature. Above 900℃, δ-ferrite was found to decompose into Chiand austenite as eutectoid, the leading phase being probably Chi. Between 700℃and 900℃, it is likely that the nucleation of austenite couldnot keep pace withthat of Chi, thus Chi was found to precipitate first and the remaining δ-ferritethen transformed to austenite. Below 700℃ the precipitation of carbides in δ-ferrite was accompanied bymartensite formation in the austenitic matrix. This may be caused by the diffu-sion of carbon from the austenitic matrix to δ-ferrite to supply the carbon re-quired for the carbide precipitation.
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    A STUDY OF "FREEZING" OF THE PYROMETRIC CONES
    CHEN HSEN-KU Institute of Metal Research; Academia Sinica
    Acta Metall Sin, 1957, 2 (1): 107-116. 
    Abstract   PDF (3522KB) ( 553 )
    The phenomenon that a pyrometric cone does not bend over at its own soften-ing temperature is called "freezing". Such phenomenon has been studied for thecones of middle temperature range (SK7-16, or ПК123-146). It is shown that the freezing of a pyrometric cone is due to the formationof certain refractory crystals from molten phases in the cone when the furnacetemperature is either unsteady or kept for a rather long period just balow its sof-tening point. In the cones SK7-10, the refractory crystals formed are of chry-santhemum shape and found petrographically to be isometric cristobalite In thecones SK11-16, apart from crystals found in SK7-10, many needle-like crystalsare formed, X-ray examination shows that they are possibly mullite. If the sodium oxide content is high relative to total alkali in cone materialSK7-10, or potassium oxide is high in SK11-16, may cause the cones to freeze.Thus in order to prepare a series of non-freezing cones the potash felspar shouldbe used as raw material for SK7-10, and soda felspar for SK11-16. It wasattempted to reduce their freezing tendency by substitution CaO by MgO intro-duced as magnesite, but the result was very unsatisfactory.
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    ОТЧЕТ ПО ОПЫТУ ИСЛЕДОВАНИЯ ЗАКАЛКИ КОНЦОВ РЕЛЬСОВ ВЫСОКОЧАСТОТНЫМ ТОКОМ
    Яо Вы-шуин;Хон Зунь-лин;Сюнь ИЁ;Нын И-зунь
    Acta Metall Sin, 1957, 2 (1): 117-138. 
    Abstract   PDF (7547KB) ( 480 )
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