Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds

Definitions

• the invention relates to an investment for model casting technology in dental technology, consisting of sand and binder, the binder being monoammonium phosphate (MAP) and Contains magnesium oxide (MGO). It also relates to the use of the investment and a method for producing such an investment.
• MAP monoammonium phosphate
• MGO magnesium oxide
• model casting work is modeled on an investment model, with Investment material overbed and at high temperatures between 900 ° C and 1050 ° C preheated and then poured.
• the preheating process is as follows: The with Investment overlayed work ("model casting muffle") is placed in the cold oven and linear (with a normal heating temperature of 2 to 9 ° C / min) to the final temperature heated up.
• the mixture is then heated linearly to the final temperature at 2 to 9 ° C./min. Also the Final temperature is then held again for 30 to 40 min until the model casting muffle is homogeneously hot. Then the work can be poured. This whole The heating process takes about 4 to 5 hours and is usually carried out at night.
• the final temperature in the model casting technique must be above 900 ° C Usually temperatures of up to 1050 ° C and possibly even higher temperatures can be achieved. This depends on the respective cobalt-chrome-molybdenum model casting alloys, which are used in model casting technology.
• the final temperature the preheating phase should be 400 to 450 ° C below the for metallurgical reasons Melting point of the respective model casting alloy.
• the muffle cools in the Casting device during the so-called casting delay time something out, so that Casting time the muffle temperature is lower than the final temperature of the preheating phase. Therefore, the muffle must not be preheated below 900 ° C, otherwise the There is a possibility of cold casting, which is absolutely avoided in dental technology must become.
• the muffle is preheated to 600 ° C Given oven, preheated at this temperature for about 30 min and then linear to a Final temperature of 900 ° C and higher heated. After a corresponding final holding time of The muffle can then be cast for approx. 40 to 60 min. With this method you get due to the higher initial temperature and a shorter linear heating certain time savings.
• sand quartz and cristobalite
• Binder mainly exists in so-called phosphate-bonded investment materials from monoammonium phosphate (MAP) and from magnesium oxide (MGO).
• MAP monoammonium phosphate
• MGO magnesium oxide
• the sand content is approximately 80 to 85% by weight and the binder content is approximately 15 to 20% by weight.
• the MAP content within the binder is often about 2 to 3% higher the MGO portion sometimes the two portions are roughly the same.
• the object of the invention is therefore to provide an investment for the model casting technique in the Dental technology and a method of creating an investment that create it enable the model casting muffle without using the investment material preheating directly in the oven preheated to final temperature (900 to 1050 ° C) to give, without causing damage to the model casting muffle.
• a further development of the invention is that the weight proportion of the binder on the Total mass of the investment is more than 20%.
• the weight proportion of the binder in the total mass is between 20% and 35%.
• the furnace temperature when the Model casting muffle is between 900 ° C and 1050 ° C.
• MAP monoammonium phosphate
• MGO Magnesium oxide
• MAP Monoammonium phosphate
• the sand consists of quartz and cristobalite.
• the invention essentially has the advantage that those with the invention Investment model cast model in the direct to final temperatures of 900 ° C and more preheated oven can be given and thus the preheating process clearly is abbreviated.
• the hot furnace can continuously with new model casting muffle be fitted without having to be cooled beforehand and then replaced with new ones Load model casting molds and heat to final temperature.
• the invention is based on the finding that the functioning of a Rapid casting process, in which the model casting muffle directly in the final temperature of 900 ° C and more preheated oven can be introduced, depends on how that Ratio of monoammonium phosphate (MAP) to magnesium oxide (MGO) in the binder of Investment is.
• MAP monoammonium phosphate
• MGO magnesium oxide
• the weight fraction of MAP of the total mass of the investment by at least 3.5% (absolute) above the MGO weight percentage.
• This information relates to sand mixtures in which approx. 8 to 12% by weight is finer Sand (fine quartz powder or fine cristobalite with a grain size d50% of less than 20 ⁇ m is present and the rest consists of coarse sand.
• finer Sand fine quartz powder or fine cristobalite with a grain size d50% of less than 20 ⁇ m is present and the rest consists of coarse sand.
• the weight fraction of MAP in the total mass must be more than 3.5% higher than that of MGO.
• This recipe contains a relatively high proportion (approx. 70%) of coarse sand (quartz sand F34 and quartz powder W3) and only 9.5% fine sand (Cristobalit M0010). So here is enough MAP share that is 3.5% above the MGO share, so that this recipe Can withstand a temperature shock of approx. 1050 ° C. With a lower reactivity of the MAP or a stronger reactivity of the MGO would have the MAP portion with the same sand shares slightly increased (e.g. to 12.3%) or the MGO share slightly decreased (e.g. to 8.2%) in order to ensure that when the model casting muffle is placed in the furnace the Temperature shock is endured. In the present case, the proportion by weight of the binder is at 20.5% of the total mass.
• This recipe has a higher proportion of fine sands than in Example 1, namely 33.7% W6 (quartz flour) and 15% SF3000 (very fine cristobalite).
• W6 quartz flour
• SF3000 very fine cristobalite

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Dental Prosthetics (AREA)
• Mold Materials And Core Materials (AREA)
• Dental Preparations (AREA)

Applications Claiming Priority (4)

Publications (1)

Family

ID=26028610

Family Applications (1)

Country Status (1)

Cited By (1)

Citations (2)

• 1997
  • 1997-08-29 EP EP97114996A patent/EP0827734A1/fr not_active Withdrawn

Patent Citations (2)

Similar Documents

Legal Events