Main technicaldata: 1, physics, chemical composition: （1）Chemical composition: The aluminum, hard, the calcium, the magnesium, the titanium five impurity element's total content, is not bigger than 0.05%. （2）Heat-stable characteristic: The test specimen in 1100℃ to 20℃ the temperature emergency, experiments three times, does not produce the crack and comes down. （3）High temperature discoloration: The test specimen fires for 1 hour under 1100℃ the temperature, do not change color.
2、Divides into four level of according to the outward appearance target