EP0491040A1

EP0491040A1 - Electrode material for glass melting furnace

Info

Publication number: EP0491040A1
Application number: EP90910178A
Authority: EP
Inventors: Toshio 3-48-11 Tajiri-Cho Masaki; Noriaki 2774-20 Mawatari Sasaki; Shin-Ichiro C-301 Aza-Tsukanoue Takaba Torata; Hiroshi 1-4-11 Ushirono Igarashi; Tetsuya 15-7 Ubakoyama Kasadera-Cho Shimizu; Tomohito 1-20-34 Ichiban Atsuta-Ku Iikubo
Original assignee: Doryokuro Kakunenryo Kaihatsu Jigyodan
Current assignee: Doryokuro Kakunenryo Kaihatsu Jigyodan
Priority date: 1989-01-09
Filing date: 1990-07-09
Publication date: 1992-06-24
Anticipated expiration: 2010-07-09
Also published as: EP0491040B1; DE69017460D1; JPH02213439A; EP0491040A4; DE69017460T2; WO1992001077A1; JPH0819505B2

Abstract

An electrode material for glass melting furnaces, having a composition comprising 25 to 40 wt% of chromium, 10 to 45 wt% of cobalt, optionally 0.1 to 1.5 wt% of titanium, optionally 0.01 to 0.50 wt% of one or a plurality of REMs, and the balance of nickel and unavoidable impurities.

Description

Technicla Field

The present invention relates to an electrode material of a glass melting furnace having an excellent corrosion resistance in molten glass in an energized state and utilizable as an electrode material of glass melting furnace.

Background Art

Examples of electrode material of a glass melting furnace which have hitherto been used include a molybdenum-base alloy comprising 10 to 60% of copper and 0.5 to 5% of barium (see Japanese Patent Laid-Open No. 88739/1974), a platinum-base alloy comprising 1 to 20% of rhodium and 0.5 to 5% of tungsten (see Japanese Patent Laid-Open No. 51124/1978), and further those using tin oxide and those using a nickel-base alloy. Examples of the nickel-base alloy include Inconel 690 which is a nickel-base alloy comprising about 30% of chromium and about 9% of iron.
Since this type of electrode of a glass melting furnace is used in molten glass in an energized state, it must have not only an excellent corrosion resistance in molten glass in an energized state but also a high melting point for the purpose of improving the operability of the melting furnace. Conventional electrode materials, however, had problems such as poor corrosion resistance im molten glass and low melting point. For example, Inconel 690 which is a nickel-base alloy comprising the above-described ingredients is not always excellent in the corrosion resistance im molten glass and has also a drawback that the melting point is as low as about 1350^oC.
The present invention has been made in view of the problem accompanying conventional electrodes particularly comprising a nickel-base alloy. An object of the present inventiion is to provide a nickel-base electrode material of a glass melting furnace which has an excellent corrosion resistance in molten glass in an energized state and a melting point above 1350^oC, i.e., the melting point of the above-described conventional nickel-base Inconel, and is suitable as an electrode material of a glass melting furnace.

Disclosure of the Invention

The electrode material of a glass melting furnace excellent in the corrosion resistance in molten glass in an energized state according to the present invention is characterized by having a chemical composition comprising by weight 25 to 40% of chromium, 10 to 45% of cobalt, optionally 0.1 to 1.5% of titanium and optionally 0.01 to 0.50% of at least one element selected from amoung REMs (rare earth metals) with the balance consisting of nickel and unavoidable impurities.
The reason for the limitation of the chemical composition (% by weight) of the electrode material of a glass melting furnace excellent in the corrosion reisstance in molten glass in an energized state according to the present invention will now be described.

Chromium: 25 - 40%

Chromium is added for ensuring the corrosion resistance of an electrode used for electric melting of glass in a glass melting furnace and is limited to 25% or more for the purpose of ensuring the corrosion resistance of such an electrode. The upper limit of the chromium content is set to 40% or less because the addition of an excessive amount of chromium not only causes the effect to be saturated but also lowers the melting point and deteriorates the toughness of the electrode.

Cobalt: 10 - 45%

Cobalt is an element useful for improving the operability of the glass melting furnace through a rise of the melting point of the electrode and, at the same time, improving the corrosion resistance of the electrode in molten glass in an energized state. The cobalt content is limited to 10% or more for the purpose of attaining the effect of raising the melting point and improving the corrosion resistance of the electrode. The upper limit of the cobalt content is set to 45% or less because the addition of an excessive amount of cobalt not only causes the effect to be saturated but also deteriorates the toughness of the electrode.

Titanium: 0.1 - 1.5%

Titanium is an element useful for improving the resistance of the electrode to molten glass in an energized state and, at the same time, attaining an improvement in the releasability of scale and may be optionally added in amount of 0.1% or more for attaining the effect of improving the above-described corrosion resistance and releasability of scale. The addition of an excessive amount of titanium, however, not only causes the effect to be saturated but also unfavorably lowers the melting point of the electrode. Therefore, when the titanium is added, the content should be 1.5% or less.

At least one member selected from among REMs: 0.01 - 0.50%

REM is an element useful for improving the corrosion resistance of the electrode in molten glass in an energized state and may be optionally added in an amount of 0.01% or more for the purpose of attaining such an effect. The addition of an excessive amount of REM, however, not only causes the effect to be saturated but also unfavorably deteriorates the toughness of the electrode. Therefore, when REM is added, the content should be 0.50% or less.

Nickel: the balance

Nickel is effective in ensuring the corrosion resistance of the electrode in molten glass as well as in improving the operability of a glass melting furnace by virtue of its high melting point. Therefore, nickel is usd as the balance.
The electrode material of a glass melting furnace according to the present invention has the above-described chemical composition and comprises nickel having a high melting point and an excellent corrosion resistance as a matrix, and a suitable amount of chromium added for the purpose of ensuring the resistance of the electrode to corrosion by molten galss, a suitable amount of cobalt added for the purpose of improving the melting point of the electrode and the resistance to corrosion by molten glass, a suitable amount of titanium optionally added for the purpose of further improving the corrosion resistance and also the releasability of scale, and a suitable amount of at least one REM optionally added for allowing voides to stay inside the alloy to further improve the corrosion resistance. By virture of this constitution, the electrode material of the present invention has an excellent corrosion resistance in molten glass in an energized state, and the high melting point thereof serves to improve the operability of the melting furnace.

Best Mode for Carrying out the Invention

Nickel-base alloys comprising various chemical ingredients listed in Tabale 1 were molten by vacuum, induction melting to prepare ingots each having a weight of 30Kg. In Table 1, Mm represents mischmetal (La + Ce) among REMs and Inconel 690 was used in Comparative Example 1.
Subsequently, each ingot was hot-forged to make a round bar having a diameter of 20 mm and a current was allowed to flow at a density of 0.8 A/cm² through the round bar at 1250^oC in a molten borosilicate glass to determine the extent of corrosion (the extent of wearing out) under immersion for 100 hr in an energized state to thereby evaluate the resistance of the electrode to corrosion by molten glass. The results are given in Table 1.

The solidus temperature of each nickel-base alloy was determined with a differential thermal analyzer. The results are also in Table 1.

Table 1

Division	No.	Chemical ingredients (wt.%)					1250^oC/100 hr, 0.8 A/cm² Extent of corrosion (µm)	Solidus (°C)
		Cr	Co	Ti	REM	Ni
Example	1	33.5	10.2	-	-	the balance	183	1393
	2	33.6	18.0	-	-	the balance	196	1401
	3	32.2	31.3	-	-	the balance	175	1408
	4	27.5	15.6	-	-	the balance	194	1414
	5	25.8	30.9	-	-	the balance	188	1433
	6	37.1	31.5	-	-	the balance	189	1399
	7	26.5	44.7	-	-	the balance	190	1436
	8	37.1	44.2	-	-	the balance	199	1413
	9	32.2	41.8	1.1	-	the balance	177	1417
	10	32.2	31.3	0.3	-	the balance	164	1402
	11	31.5	30.8	1.3	Y:0.09	the balance	185	1381
	12	33.1	30.9	-	Y:0.34	the balance	132	1380
	13	30.9	34.2	0.2	Mm:0.15	the balance	146	1387
	14	29.1	28.2	1.3	Mm:0.03	the balance	167	1362
Comp. Example	1	28.6	Fe:9.0	0.32	Al:0.28	the balance	356	1341
	2	33.6	<0.01	-	-	the balance	216	1378
	3	32.2	52.2	-	-	the balance	254	1414
	4	42.0	<0.01	-	-	the balance	209	1356
	5	42.0	15.9	-	-	the balance	207	1363
	6	20.2	40.3	-	-	the balance	211	1430

As is apparent from the results given in Table 1, the electrode materials comprising nickle-base alloys of Examples 1 to 14 according to the present invention exhibited a less extent of corrosion in a molten borosilicate glass in an energized state, i.e., were found to have a superior resistance to corrosion by molten glass in an energized state. Further, they had a melting point above that of Inconel 690 (Comparative Example 1) which is a conventional nickel-base alloy, i.e., have been confirmed to be able to improve the operability of a glass melting furnace.
By contrast, the nickel-base alloys of Comparative Examples 1 to 6 exhibited a larger extent of corrosion in molten glass in an energized state. This brings about a problem of durability when then are used as an electrode material. Further, some of them has a low melting point.
The electrode material of a glass melting furnace according to the present invention has a composition comprising by weight 25 to 40% of chromium, 10to45% of cobalt, optionally 0.1 to 1.5% of titanium and optionally 0.01 to 0.50% of at least one element selected from among REMs with the balance consisting of nickel and unavoidable impurities and, by virture of this constitution, brings about such a remarkably excellent effect that it exhibits an excellent resistance to corrosion by molten glass in an energized state when used as an electrode material of a glass melting furnace and, at the same time, improves the operability of the glass melting furnace because of its higher melting point than that of Inconel 690, i.e., the conventional nickle-base alloy.

Claims

An electrode material of a glass melting furnace having an excellent corrosion resistance in molten glass in an energized state, characterized by comprising by weight 25 to 40% of chromium and 10 to 45% of cobalt with the balance consisting of nickel and unavoidable impurities.
An electrode material of a glass melting furnace having an excellent corrosion resistance in molten glass in an energized state, characterized by comprising by weight 25 to 40% of chromium, 10 to 45% of cobalt and 0.1 to 1.5% of titanium with the balance consisting of nickel and unavoidable impurities.
An electrode material of a glass melting furnace having an excellent corrosion resistance in molten glass in an energized state, characterized by comprising by weight 25 to 40% of chromium, 10 to 45% of coblat and 0.01 to 0.50% of at least one element selected from among rate earth metals with the balance consisting of nickel and unavoidable impurities.
An electrode material of a glass melting furnace having an excellent corrosion resistance in molten glass in an energized state, characterized by comprising by weight 25 to 40% of chromium, 10 to 45% of cobalt, 0.1 to 1.5% of titanium and 0.01 to 0.50% of at least one element selected from among rate earth metals with the balance consisting of nickel and unavoidable impurities.