:הרכב המתכת ניקל = 76% כרום = 13.5% !!!ללא בריליום הוראות עבודה Waxing - the patterns may be waxed and cast from 0.2 mm to 0.3 mm. this minimizes metal finishing and allows more room for porcelain, thus enhancing porcelain shades. Spruing - the indirect spruing technique is recommended using a runner bar the size of a pencil. (inlay wax sticks work well) for spruing, use 10 gauge for copings and 6-8 gauge or larger for pontics. The length of the sprues, from the runner bar to the pattern, should be 1/4 to 3/8 inches long. Investing - a high investment – carbon free investment is recommended. follow the manufacturers investing procedures using a non alcohol debubblizer: but rinse off the debubblizing solution thoroughly. fill the ring only one eighth inch above the patterns. Burnout – two methods may be employed for burning this ceramic alloy: 1. place the ring or the rings directly into a 982 C deegres (1800 F) over. heat soak for 15 sec per gram ( example: for 90G ring = 23 min) plus 10 min for each additional ring. Than make your casting. 2. place the ring or the rings in a cold oven raise the temperature to 927 deegres ( 1700F ) and heat soak for 45 min or longer. Prior to casting increase the temperature up to 982C (1800F ) and cast. Important – do not heat soak at 982C (1800F ). The added heat from 927C to 982C is to correct for heat loss from the time the ring is out of the oven. Melting And Casting – this ceramic alloys may be melted by induction melting or with gas oxygen torch. 1. for induction melting, the casting temp is 1329C (2425F). 2. when using a gas oxygen torch, it is important that the torch have a multi – orifice tip and the capacity to melt 2-3 ingots in 12-14 sec. unlike precious alloys. Base ceramic alloys are melted with volume of heat instead of concentrated, intense heat. As a result, the oxygen setting should be 35-40 p.s.i ( if propane is used – the setting should be less then 2 p.s.i ). 3. pre- heat quartz cruciblre with the torch. Place the ingots in crucible and heat them to an orange – red hue. Next take the ring out of the oven and place it in the casting cradle. At this point bring the torch down one inch from the top of the ingots. When the ingots lose definition and puddle, release the casting arm. It is very important not to leave the ring out of the oven longer then 4 sec prior to casting, due to the fact that there is an extreme drop in the temp of the ring in matter of sec. Metal Finishing – IMPORTANT – from this point on, not touch the porcelain bearing surface with your fingers. 1. air abraide the porcelain – bearing with brazillian reddish – brown aluminum oxide – reddish brown aluminum oxide creats a greater catalytic effect on the surface then white aluminum oxide. The end result is en increase in the porcelain – metal bond. 2. rinse with distilled water in an ultrasonic for 1-2 min. Oxid Firing (Degassing) - 1. to create a desirable oxide, place the metal work in a porcelain oven at 538C ( 1000F ). 2. unde full vacuum, raise the temp 55C per min to 977C (1790F) but no higher then 982C (1800F). 3.the surface of the metal should have a straw or golden colored oxide. However if the metal surface exhibits a bluish tint with some straw colored patches, it is okay to proceed to the opaque application. If the straw colored oxide is not achieved each time, do not be concerned. If the metal exhibits a dark red browm oxide, this is an indication that the oxide firing was too high. In this instance, disc off the oxide, expose new metal, air abrade and repeat the oxide firing. Physical and mechanical properties of the ceramic alloy Co – efficient of thermal expansion - 13.9 at 0-500 degrees C Hardness - 225 Specific gravity - 7.7 gr/cc Yield strength - 72,000 psi Tensile strength - 164,000 psi Elongalion - 11% Melting range - 1204-1302 degrees C Casting temp - 1329 degrees C Composition of ceramic alloy Ni = 76% Cr = 13.5% Mo = 6% This ceramic alloy is manufactured according to DIN EN ISO 9002/08.94 **DIN EN 46002/09.96 **ADA specification NO.38 for metal ceramic systems **MDD 93/42/EEC class 2 device standards.