Metal bonding glass-ceramic compositions having improved hardness

• US 3,977,857 A
• Filed: 08/07/1975
• Issued: 08/31/1976
• Est. Priority Date: 10/29/1973
• Status: Expired due to Term

• Current Assignee: ABB Power T&D Co Inc (ABB Limited)
• Original Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Inventors: Mattox, Douglas M.
• Primary Examiner(s): Whitby, Edward G.
• Application Number:
  US05/602,706
• Time in Patent Office: 390 Days
• Field of Search: 65/33, 65/43, 65/49, 65/59 R, 156/89, 156/242, 106/39.7, 106/48, 174/137 R
• US Class Current: 65/33.5
• CPC Class Codes: C03B 19/02 by casting molten glass, e.g. injection moulding
• CPC Class Codes: C03B 32/02 Thermal crystallisation, e.g. for crystallising glass bodies into glass-ceramic articles C03B27/012 takes precedence
• CPC Class Codes: C03C 10/0009 containing silica as main constituent
• CPC Class Codes: C03C 10/0045 containing SiO2, Al2O3 and MgO as main constituents
• CPC Class Codes: C03C 27/02 by fusing glass directly to metal
• CPC Class Codes: H01B 19/00 Apparatus or processes specially adapted for manufacturing insulators or insulating bodies manufacture of porcelain for electric insulation C04B33/26
• CPC Class Codes: H01B 3/087 Chemical composition of glass
• CPC Class Codes: H01B 3/088 Shaping of glass or deposition of glass

Abstract

A metal member is coated with or embedded in a high-magnesia glass-ceramic material having the approximate composition of about 60 to 80 weight percent SiO₂, 12 to 20 weight percent Li₂ O, 2 to 14 weight percent MgO, 1.5 to 6 weight percent P₂ O₅, 1 to 7 weight percent of an alkali oxide selected from the group consisting of K₂ O and Na₂ O and their mixtures, 0 to 2 weight percent of a transition metal oxide selected from the group consisting of Co₃ O₄, MnO₂, Fe₂ O₃, V₂ O₅ and WO₃ and their mixtures, 0 to 5 weight percent PbO, 0 to 2 weight percent Al₂ O₃ and 0 to 1 weight percent As₂ O₃.

Claims

1. A method of bonding a glass-ceramic material to a metal member comprising the steps of:

A. forming a fluid glass composition consisting essentially of about 60 to 80 weight percent SiO₂ 12 to 20 weight percent Li₂ O, 2 to 14 weight percent MgO, 1.5 to 6 weight percent P₂ O₅, 1 to 7 weight percent of an alkali oxide selected from the group consisting of K₂ O and Na₂ O and their mixtures, 0 to 2 weight percent of a transition metal oxide selected from the group consisting of Co₃ O₄, MnO₂, Fe₂ O₃, V₂ O₅ and WO₃ and their mixtures, 0 to 5 weight percent PbO, 0 to 2 weight percent Al₂ O₃ and 0 to 1 weight percent As₂ O₃ ;

B. applying the glass composition directly to a metal member;

C. cooling the glass to a temperature of below about 600°

C;

D. heating the glass and metal member up to a temperature of about 900°

C at a rate of about 10°

-80°

C per hour, to form a glass-ceramic from the glass composition which intimately bonds directly to the metal member, said glass-ceramic being a substantially homogeneous microcrystalline mass of ceramic having a Knoop handness value of over about 660 in a glass matrix;

E. maintaining the temperature of the glass-ceramic bonded metal member for about 1/2-10 hours;

F. cooling the glass-ceramic bonded metal member to room temperature.

2. The method of claim 1, wherein the glass is formed in step (A) by heating at a temperature between about 1000°

to 1500°

C and the glass composition is applied to the metal member in step (B) by pouring the glass composition into a mold containing the metal member, to embed the metal member in the glass composition.

3. The method of claim 2, wherein the metal member has a coefficient of thermal expansion of between about 8 ×

10.sup.^-6 in/in/°

C and 18 ×

10.sup.^-6 in/in/°

C and the glass-ceramic bonded metal member is cooled in step (F) over about a 6 to 48 hour period.

4. The method of claim 3, wherein the mold is preheated and the metal member has a coefficient of thermal expansion of between about 8 ×

10.sup.^-6 in/in/°

C and 13 ×

10.sup.^-6 in/in/°

C, a relatively smooth surface and is oxidized before step (C) to form a dense oxide layer thereon having a thickness of between about 0.8 to about 10 microns.

5. The method of claim 3, wherein, in step (D) the P₂ O₅ nucleates crystals of lithium phosphate which form sites for growth of lithium metasilicate crystals, which lithium metasilicate crystals in turn form sites for growth of lithium disilicate crystals and wherein the ceramic phase constitutes 60-95 volume percent of the glass-ceramic.

6. The method of claim 3, wherein the composition contains about 4-12 weight percent MgO, 2 to 4 weight percent P₂ O₅ and 0 weight percent Al₂ O₃.

7. The method of claim 4, wherein the oxidized metal member has a thin pre-glassed coating on the oxide layer.