Frequently Asked Questions

Product Information

What materials are your crucibles made of?
Where are your crucibles manufacturerd?

Product Recommendations

What type of crucibles does Molten Metal Systems recommend for ZnO production?
What type of crucibles can be used for melting in induction furnaces?
What crucibles are recommended for different applications (Al, Cu, Zn, Precious Metals, etc)?
Can I re-use the stand (pedestal, base block) after the crucible has been removed?
For which patterns can we get reinforced crucibles?
May I use Excel E in gas furnace?
May I use standard Excel stand with Excel E crucible or the opposite?
What is the primary difference between Excel brand and Omnimelt brand?
Can I use a crucible without a stand (pedestal, base block)?
What kind of packing is used to protect your crucible during transportation?
Can I use the same brand/type of crucible in gas burner furnaces as with an oil burner furnace?
Can I fill a cracked or damaged crucible with plastic (Al2O3 + P2O5) and continue my work?
What are the advantages and disadvantages of SiC vs. CG? Why would I choose one over the other?
I have heard that Molten Metal Systems is the only global crucible manufacturer that uses all three crucible forming techniques. Why is this and why does this set Molten Metal Systems apart from the competition?

Performance Issues

What is a typical crucible life time?
How can I improve my crucible life and performance?
How I can eliminate problems with flux attack and lengthen crucible life time?
How I can prevent bottom cracking?
How I can prevent crucible early oxidation resulting in crucible cracks on top edge?
Why are there different preheating procedures for different crucibles and does it really matter?
If I don’t clean the crucible regularly, what can happen? How often do I need to clean the crucible?
How long is the pre heat for first use ? Can I use it for gas or oil fired burners?
How long is the first heat for precious metals if I use a gas fired burner or an oil fired burner?
What is the crucible installation procedure for bale out and tilting furnaces?

Foundry Products

Do you have only one size of impeller on your degassing rotor?
What is the normal nitrogen flow for degassing rotors and degassing tubes?
 

What materials are your crucibles made of?

Molten Metal Systems crucibles are manufactured using carefully selected materials designed to precisely match the crucible’s characteristics and operational performance to each customer’s metal melting, holding or transfer application. A foundry crucible contains 30-50% by weight of flake graphite, depending on the properties required. Naturally occurring graphite is normally used. The carbon content of graphite imparts high thermal conductivity and non-wettability and, coupled with its plate-like layered matrix structure, provides high thermal shock resistance. This is critical to foundry applications as temperatures can change by several hundred degrees in seconds. In addition, crucibles will normally contain 10-50% silicon carbide – depending on the desired properties. Unlike graphite, silicon carbide is synthetic, manufactured from silica sand. This material provides excellent resistance to elevated temperature erosion and to chemical corrosion. It also imparts thermal conductivity. Choosing the best grain size and structure is important for optimizing the overall microstructure to match the product to specific applications. There are two types of bonding systems used in crucibles. Tar/resin produces carbon bonds and the other - clay, produces ceramic bonds following heat treatment. >>Top

Where are your crucibles manufactured?

Molten Metal Systems crucibles are manufactured in several plants strategically located around the world. Our facilities can be found in Germany, Brazil, India and China. >>Top

Product Recommendations

What type of crucibles does Molten Metal Systems recommend for ZnO production?

There are several types of crucibles that we can recommended for this application including our ISO-pressed crucibles made from our Syncarb Z2 material, a specially designed mix of clay graphite. Our Syncarb Z2 products have the optimized shape and the high density required for this application. It is approved and used by many Zinc Oxide producer all over the world. Contact your Molten Metal Systems representative to get the right crucible for your application. >>Top

What type of crucibles can be used for melting in induction furnaces?

Molten Metal Systems offers many options for melting in induction furnaces. In order to offer the correct product for your application you will need to provide: a) the furnace working frequency in Hz, b) the furnace operating power in kW, c) the metal to be melted and d) the metal melting temperature. With this information we can recommend right product for the application. >>Top

What crucibles are recommended for different applications (Al, Cu, Zn, Precious Metals, etc)?

Molten Metal Systems provides solutions for most melting requirements. The specific crucible for a particular application depends upon several factors including furnace type, metal to be melted, and other applications variables. In order to correctly identify the best crucible for your application please contact one of our sales people in your region. >>Top

Can I re-use the stand (pedestal, base block) after the crucible has been removed?

Molten Metal Systems strongly recommends that a new stand be used whenever replacing the crucible. >>Top

For which patterns can we get reinforced crucibles?

The most common type of crucible that can be reinforced is the roller formed type. The process for manufacturing reinforced wall crucibles is less costly for roller formed crucibles. >>Top

May I use Excel E in gas furnace?

Excel E can be used in gas furnaces when melting or holding Aluminum but only when a light (or no) flux is used. Excel E can also be used in a gas furnace for Zinc Oxide production. >>Top

May I use standard Excel stand with Excel E crucible or the opposite?

Using a standard Excel stand (pedestal, base block) with an Excel E crucible is not recommended. >>Top

What is the primary difference between Excel brand and Omnimelt brand?

The mixture of raw materials that are used to produce the products are different for the two products. >>Top

Can I use a crucible without a stand (pedestal, base block)?

A crucible can be used without a stand (pedestal, base block) in an induction furnace. A stand (pedestal, base block) must be used in all other types of furnaces. >>Top

What kind of packing is used to protect your crucible during transportation?

Molten Metal Systems uses a variety of packing materials to ensure its products are protected in the best possible way for their transportation to customers. Smaller crucibles are packed in cardboard box with packing material insulation to provided added protection. Larger crucibles are packed using wood pallets and strapping to ensure they do not move during shipping. >>Top

Can I use the same brand/type of crucible in gas burner furnaces as with an oil burner furnace?

Typically you can use the same type/brand of crucible in a gas burner furnace as you can in an oil burner furnace. >>Top

Can I fill a cracked or damaged crucible with plastic (Al2O3 + P2O5) and continue my work?

Molten Metal Systems does not recommend that any cracked or damaged crucible be repaired. MorganMMS highly recommends that damaged or cracked crucibles be taken out of service immediately for safety reasons. >>Top

What are the advantages and disadvantages of SiC vs. CG? Why would I choose one over the other?

The advantages of a given product over another depends primarily on the working temperatures and heating cycles of the application. SiC products versus rib formed clay graphite will typically have better thermal conductivity. SiC versus isotatic pressed clay graphite will have better thermal shock resistance. >>Top

I have heard that Molten Metal Systems is the only global crucible manufacturer that uses all three crucible forming techniques. Why is this and why does this set Molten Metal Systems apart from the competition?

Molten Metal Systems has a long history in the crucible industry. Over the years it has experimented and perfected manufacturing techniques that are critical to the production of high quality and top performing crucibles. The three forming techniques that Molten Metal Systems has perfected are roller forming, rib forming and ISO static pressing. Each of these methods are used to provide our customers with the quality products manufactured by us. >>Top

Performance Issues

What is a typical crucible life time?

Each application is different. Crucible life depends on a number of variables including furnace type, metal melted, flux usage, operator practices, etc. To get the optimal life out of your crucible, use a Molten Metal Systems crucible recommended by your local sales person. >>Top

How can I improve my crucible life and performance?

There are several key activities that will help to ensure you optimize your crucible life and performance. While the product quality built into a crucible by its manufacturer is one key to long service life, another key is held by metal casters themselves. That key is providing the best possible crucible care on the job. Choosing the right crucible, handling your crucible with care and proper installation will make an important contribution to crucible service life. In addition, proper preheating of the crucible before first use and caring for your crucible during normal operations will help to make the crucible last as it was designed*.
By working closely with your Molten Metal Systems representative to select the right crucible for your melting, holding or metal transfer operation you will be eliminating potential applications issues. Upon receipt of your crucible, be sure to inspect it carefully and handle it with care when moving it to storage or to your furnace. Install it properly according the Molten Metal Systems installation procedures. Preheat it according to the Molten Metal Systems guidelines. Operate it within its design parameters. Protect it from physical and thermal damage. And replace it immediately when it is damaged or worn. Follow these rules and your crucibles will provide excellent service life, operational efficiencies and significant economies.
*Refer to the Molten Metal Systems installation and heating procedures when first installing and initially using your crucible. Refer to the article on our website entitled “Key Steps To Maximizing Your Crucible’s Service Life” to find tips and guidelines for getting the most performance out of your crucible. >>Top

How I can eliminate problems with flux attack and lengthen crucible life time?

Use only limited amounts of flux at the specified temperatures and for limited time. First, make sure that the metal has been completely melted. Next add flux and mix it thoroughly with the metal. Make sure to clean all the ash and oxides from the crucible during the melt and after it has been emptied. Be sure to clean the crucible in the hot stage often. Molten Metal Systems recommends the use of Excel Tricoat PD to for optimal crucible life if the fluxes are borax or NaCl (used normally in copper / cpper alloys and precious metal). If using Sr and Na fluxes in aluminium alloys, Molten Metal Systems recommends our Syncarb or Alustar crucibles. >>Top

How I can prevent bottom cracking?

Use the correct stand (pedestal, base block) size as recommended by your Molten Metal Systems representative. The stand should be made from the same material as the crucible material. Preheat the crucible carefully according to Molten Metal Systems recommendations. Do not use any parting refractory material to separate the crucible from the stand. >>Top

How I can prevent crucible early oxidation resulting in crucible cracks on top edge?

You must ensure that the furnace burner is adjusted correctly. The furnace chamber must be closed to prevent air access in to melting chamber. The top edge of the crucible should be covered with a furnace ring that is of the correct size. >>Top

Why are there different preheating procedures for different crucibles and does it really matter?

Crucibles are made of different materials with different properties. So they may require different preheating procedures. Discuss with your local representative if you have questions. >>Top

If I don’t clean the crucible regularly, what can happen? How often do I need to clean the crucible?

Normally the crucible should be cleaned after each melt or at least once per shift in holding applications, or any time that dross starts to become stuck on the crucible’s inside surface. If dross is not cleaned from the crucible, then it is likely that during the next heating the dross (with a much higher thermal expansion than the crucible material ) will cause a crack in the crucible wall. >>Top

How long is the pre heat for first use ? Can I use it for gas or oil fired burners?

To get the correct instructions for preheating please consult your local representative or view our Installation and Heating procedures on this website. >>Top

How long is the first heat for precious metals if I use a gas fired burner or an oil fired burner?

To get the correct instructions for preheating please consult your local representative or view our Installation and Heating procedures on this website.  >>Top

What is the crucible installation procedure for bale out and tilting furnaces?

All furnaces have different designs and therefore should be dealt with individually. Please consult your local representative or view our Installation and Heating procedures on this website. >>Top

Foundry Products

Do you have only one size of impeller on your degassing rotor?

No, we can supply a range of diameters to suit customer’s applications. Our standard degassing rotor has a 6 vane impeller which is 150mm diameter with a 75mm dia shaft with a variety of couplings to suit customers degassing machines. We can also supply a larger 6 vane impeller in diameters ranging from 180 to 200mm with shaft diameters from 75mm to 90mm. >>Top

What is the normal nitrogen flow for degassing rotors and degassing tubes?

The normal nitrogen flow rate is approximately 20 litres per minute, degassing aluminium requires 20 litres of nitrogen per minute for every 100kg of aluminium to be treated, so 1000kg of aluminium needs to be treated for 10 minutes with the nitrogen set at 20litres per minute. In practice these times can be adjusted to suit local conditions. When using an open degassing tube the nitrogen flow rate should be set at 5 litres minute, using higher flow rates will waste gas as the bubbles will be larger and not as well dispersed as when using a degassing rotor. >>Top