EFFECT OF THE C O M P O S I T I O N OF THE BATH ON THE TEMPERATURE~

OF E L E C T R O C H E M I C A L B O R I D I N G OF STEEL

(UDC; 621.785.53 : 621.317.729)

V. P. G a l u s h k o , V. L . M a s a l ' s k i i o ~. S. V a r e n k o , and Yu. M. I v a n c h e n k o - L i p s k i l

Dnepropetrovsk State University Translated fzom Metallovedenie i Termicheskaya Obrabotka Metallov, No. 11. pp. 40-41, November, 1965

The purpose of our investigation was to study the viscosity of molten electrolytes as a function of the concen- tration of sodium carbonate added to it at 800, 850, and 960"C. According to the pubiished data [1], sodium car- bonare is decomposed at high temperature with the formation of Na~K) and COe, and therefore the addition of sodi- um carbonate does not in fact change the composition of the electrolyte. Only tl'~ ratio between sodium and boron oxides changes, and this decreases the melting point considerably.

Before the meast~ements were made, the components were smelted at 1000"C. To measure the viscosity we made a beaker of KhN.TST steel with a calibrated removable capillary. The t /me it took for a certain volume o f the melt to pass through the capillary was the arbitrary measure of the visco~ityo The apparatus for the measure ' merit of viscosity is shown in Fig. 1. The crucible furnace 9 was heated to the desired temperature which was con- trolled with a p la t inum-plat inum-rhodium thermocouple 3 and a pyrometea 1. The mixture to be tested was poured into the vessel 8 with the conical valve 7 of the capillary closed and was kept at a given temperature for 30 rain. Then the t ime the melt passed through the capillary was measured with a stop watch with a second hand. The melt pouring out of the vessel passed into the receivinR Vessel 2 and can be used again forrepeared experiments.

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Fig. 1. Diagram of the apparatus for determining the time it takes for the melt to flow through the caplllarys 1) pyrometer; 2) vessel into which the melt pours; 3) thermocouple; 4) lining; 5) spiral heater; 6) calibrated capillary; 7) closing valve; 8) metal beaker; 9) jacket of the furnace; 10) fur- nace cover; II) beaker holder; 12) support.

The results of measurements representing the variation of the time of pouring of the melt with temperature ate shown in Fig. 2. The time it takes foe the melt to pass through the capillary (and, consequemly, the viscosity of the melt) decreases with increasing temperature according to the same relatiomhip for all compositions of the melt.. An increase of the amount of sodium carbona~ in the melt decreases the viscosity of the melt. For example, when the concentration of sodium carbonate in the melt is increased by ~ the time it takes for the melt to pass through the ca- pillary decreases by a factor of L5 at 800~

The dependence of the viscosity of the melt on the concentration of sodiumcarbonate at 800. 850. 900. and 960"(; is shown in Fig. 3. Figures 2 and 3 indicate that the decrease in viscosity resulting from the addition o f 30% so- dium carbonate is not a limit decrease, but further increase in the concentration of sodium carbonate seems unreasonable. The decrease in the temperature of the molten electrolyte as the result of the addition of sodium carbonate decreases the diffusion rate of boron,. We tested the electrolyte con- taining 30% borax. 40~ bode anhydride, and 30~ sodium carbonate. The results of borlding were satisfactory and the working temperature was reduced to 800-820"C.

"/53

rain

I $ ,

..r #

600 B$# 800 950 "s

Fig. ~ Dependence of the t ime the melt takes to.pass through the capil- lazy on the temperature. The num- bers on the curves indicate the num- ber of the reek.

rain

"\ v ~

, \ It % ~ %

la zO aa Na~.% @,

Fig. 3. Dependence of the t ime it takes for the melt to pass through the capillary {min) on the concen- tration of sodium earixmate: 1) 800"C.; 2) 850"C; 3) 900"C; 4) 96o*c.-

SUMMARY

L The vimodty of the electrolyte decrease.s comiderably with the addition of up tO 30~ t~lium carbonate~ This makes it possible to decrea~ the boriding temperature-to 800-89-0"C.

2. We p r o ~ the use of the following e!ectroIyte for electrolytic boriding: 30~ borax, 40~ boric anhydride, and 30~ sodium carbonate.,

LITERATURE CITED

L V.D. Taran and L. P. Skugorova. MiTOM (1MO)o No. 1. 2. V .D. Taran and L. P. $kugorova, Vesmik mashinomoeniya (1957), No. 5. 3. M.E. Blamer and N. P. Besedin. MiTOM (1955), No. 6. 4. N, N. Nogtev, Byulleten' izobretenii {1961), NO. 1L 5. A. PetLcol'd, l~mal" (1958). No. 1.

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