Method of strengthening ceramic material by glazing and quenching

Abstract

Abstract A METHOD OF INCREASING THE STRENGTH OF A CERAMIC BODY HAVING A BODY THERMAL EXPANSION COEFFICIENT AND A BODY SOFTENING TEMPERATURE. THE SURFACE OF THE BODY IS COATED AT LEAST ONCE WITH A GLAZE WHICH HAS A GLAZE THERMAL EXPANSION COEFFICIENT AND WHICH HAS A GLAZE SOFTENING TEMPERATURE WHICH IS LOWER THAN THE BODY SOFTENING TEMPERATURE, AND WHICH HAS A MINIMUN FIRING TEMPERATURE INTERMEDIATE SAID BODY SOFTENING TEMPERATURE AND SAID GLAZE SOFTENING TEMPERATURE. THE COATED BODY IS FIRED AT LEAST ONE TIME TO A TEMPERATURE HIGHER THAN THE GLAZE FIRING TEMPERATURE, AND THE BODY SOFTENING TEMPERATURE AND LOWER THAN THE MELTING POINT OF THE MATERIAL OF THE BODY. THE GLAZED FIRED BODY IS QUENCHED IN A QUENCHING MEDIUM AT AN AVERAGE SURFACE COOLING RATE TO AT LEAST 10* C./SEC., AND AT A RATE BELOW THAT WHICH WILL CAUSE THERMAL SHOCK FROM THE FIRING TEMPERATURE TO A TEMPERATURE BELOW THE GLAZE SOFTENING TEMPERATURE FOR FIRST CAUSING MORE RAPID COOLING OF THE EXTERIOR OF THE BODY THAN THE INTERIOR FOR CAUSING PLASTIC FLOW IN THE INTERIOR OF THE BODY AND PRODUCING POSITIVE COMPRESSIVE STRESSES IN THE EXTERIOR OF THE BODY, AND THEN PASSING THE BODY SOFTENING TEMPERATES, FOR CAUSING THE GLAZE TO BE PLACED UNDER A POSI- TIVE COMPRESSIVE STRESS RESULTING FROM THE DIFFERENCE BETWEEN THE PRODUCT OF THE BODY EXPANSION COEFFICIENT AND THE TMEPERATURE CHANGE OF THE BODY BELOW THE BODY SOFTENING TEMPERATURE AND THE GLAZE EXPANSION COEFFIEICNT AND THE TEMPERATURE CHANGE OF THE GLAZE BELOW THE GLAZE SOFTENING TEMPERATURE. BY THIS METHOD THE BENDING STRENGTH OF THE BODY IS INCREASED AS COMPARED WITH AN UNGLAZED AND UNFIRED BODY OF THE SAME CERAMIC.

Inventors

• 👤 H Kirchner

Bibliographic Details