Investigation on Uncoventional Coarsening of W Powder by Alkali Metal Elements during WO_3 Reduction

SUN Bao-qi;WU Guo-long;CHEN Yi-ming

Rare Metals and Cemented Carbides | Vol., Issue 4, 1998 | pp. 1-6

The characters and differences of unconventional coarsening of W powder caused by Li, Na, K are studied in the paper. It reveals that Li is the optimum element for coarsening of W Powder. Very coarse crystal W powder with an average particle size of 100μm is obtained when doping amount of Li is not less than 400ppm and reduction temperature is not lower than 1000℃.

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Influence of Nb Raw Material's Grain Size on Their Indirect Carbon Reduction Duration

HE Kun-chi

Rare Metals and Cemented Carbides | Vol., Issue 4, 1998 | pp. 6-10

Research was made on influence of raw material's grain size on Carbon reduction duration. The results show that the grain size is the key factor influencing the reduction duration.Proper size proportion of Nb2O5 and NbC can lower the reaction time, averagely from 16h. to 12 h.

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The Effects of Forming Agent on the Forgeability of Steel-bonded Cemented Carbides

WANG Che;XIANG Zhi-lei;ZHOU Mei-ling

Rare Metals and Cemented Carbides | Vol., Issue 4, 1998 | pp. 11-14

The differences of powder fluidity oxidability and compaction pressure between the powders with or without forming have been studied in this paper. The results show that forming agent will eliminate the compact's defects during compaction and sintering and improve the blank. Analysis is made of the effect of porosity of sintering compact on the fracture property of large-size tungsten carbide grain and the plastic fluidity of steel substrate during forging.

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Study of Non-homogeneous Hard Alloys and Its Application in Hard-rock Drilling Tools

ZHOU Shu-zhu

Rare Metals and Cemented Carbides | Vol., Issue 4, 1998 | pp. 15-20

Based on the average WC particle size and distribution in the powder and alloy, according to alloy's WC subcrystalline size, microstrain and Co-phase distribution, study is made of the influence of we particle size compositions and Co phase distribution on the physical mechanical properties of mining cemented carbides. The cemented carbides with a combination of non-homogeneous Co-phase and non-homogeneous hard phase has been satisfactorily used for hard-rock drilling tools.

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Effect of Ball-milling Conditions on the Properties of Steel-bonded WC Hard Alloy

ZHANG Yu-hua;LU Wei-min;YANG Xuan-zeng

Rare Metals and Cemented Carbides | Vol., Issue 4, 1998 | pp. 21-24

In this paper the influence of ball-milling conditions of steel-bonded WC hard alloy on the properties has been investigated. By altering ball-milling conditions, uniformity of powder mixture can be improved to obtain steel-bonded WC hard alloy with the uniform microstructure and good performance.

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Experimental Study on the Relationship Between the Wear and the Thermoelectric Property of YS25 Cemented Carbide Insert

CHEN Shun-qing;YUAN Zhen-bo;WANG Gang

Rare Metals and Cemented Carbides | Vol., Issue 4, 1998 | pp. 25-27

The relationship between the wear and the thermoelectric poverty of YS25 cemented carbide inserts has been experimentally studied in this paper. Then the corresponding experimental formula is established.

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Electrical Conductivity of NdF_3-NaF-LiF Melt

CHEN Jian-she;XU Xiu-zhi;HUANG Yong-chun

Rare Metals and Cemented Carbides | Vol., Issue 4, 1998 | pp. 28-30

Conductivity of NdF3-NaF-LiF melt is studied by means of threes factor linear orthogonal regression design, and mathematical model about that is presented. Effects of content of NdF3, molar ratio of NaF to LiF, temperature on conductivity are discussed.

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Study of High-efficiency Recovery of Ta from Their Scraps

XU Ling-bin

Rare Metals and Cemented Carbides | Vol., Issue 4, 1998 | pp. 31-35

Study is made of Ta scraps treatment by reducing sintering in combination with pickiling-hydriding-crushing. The results show that metallurgical Ta powder and Ta products can be obtained from Ta scraps with the said process, resulting in remarkable economic profits.

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Preparation Method for Ultrafine Carbide Powder

CHEN Wei-liang;ZHONG Hai-yun;DAI Yong-nian

Rare Metals and Cemented Carbides | Vol., Issue 4, 1998 | pp. 36-41

Several kinds of methods and principles for preparing ultra fine Carbide powder were discussed and compared. It was found that agitation-ball milling is an effective method for preparing ultrafine powder.

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Progress in Purification of Na_2 WO_4 Solution

CAO Shu-hong

Rare Metals and Cemented Carbides | Vol., Issue 4, 1998 | pp. 42-46

The research results of the removal of several common and typical impurities, such as arsenic phosphorus silicon molybdenum etc. from impure sodium tungestate solution are reviewed and several commonly used purification methods are reported with discussion of research trend.

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