Note: Also see this link for other FAQ's related to this important topic.
Q: I need graphical information about molybdenum's electrical properties and also thermal expansion properties. Where can I find this data?
A: See Figure 5 and Figure 6 below and contact bkengineering@lycos.com for more information.
Q: For my upcoming project I am considering the use of moly-tungsten alloy, specifically Mo-30W (30% wolfram). How strong is this material?
A: Here is a chart showing the strength of Mo-30W along with the strength of TZM, unalloyed moly and low carbon unalloyed moly. As the chart shows, Mo-30W is fairly strong, peaking at 120 ksi at low temperature, but the strength diminishes to approx. 33 ksi at 2500 deg F.
Q: I need to know about face milling of molybdenum. What can you tell me?
A: For face milling operations, the conventional carbide or carbide-tipped face mills designed for use on cast iron can be used. High-speed steel will also work work but steel will wear out quickly. Tool angles are the same as used on cast iron. Cuter conditions should be checked frequently and workpiece backup plates should be used, especially for heavy stock removal procedures such as hogging out.
Rough cutting of molybdenum in depths of .05 to .10 inch calls for speeds of 100-160 feet per minute at an average feed rate of .005 inches of feed per tooth. Finish cuts are made mainly at speeds of 350-400 fpm with a range on the depth of cut from 1 to 3 mils. The feed rate is in the range of 4-5 mils of feed per tooth.
Be careful to avoid corner and edge breakout, especially when using multiple heads. A cutting fluid of soluble oil is preferred.
Q: What about drilling molybdenum? What are some tips and pointers?
A: Here are some tips:
-Beware of drill binding
-Use drill bushings when possible
-Standard high-speed steel drills are used with a 118 deg angle to provide maximum drilling efficiency
-Solid carbide drills can be used for holes under 3/8 inch
-Crankshaft points should be considered because they reduce heat build-up
-When drilling through holes, the workpiece should be backed up to prevent edge breakout
Q: What is some general molybdenum griding information?
A: Grinding of molybdenum should be used for finishing not for roughing. Molybdenum can fall victim to surface heat checking and for that reasn soft wheels are used and they should be properly dressed. Carborundum wheels # GA-463-J6-V-10 can be used for rough grinding and # PA-60-H8-V40 can be used for contours and finishing. Soluble oil mixtures are recommended over highly chlorinated or highly sulfurized fluids.
Q: Can I flame cut molybdenum sheets?
A: No, this is not recommended. Also, allow 1/8" for kerf and 3/16" for camber on heavy sections if sawing molybdenum sheets.
Q: Are EDM and ECM used for molybdenum material applications?
A: Yes, this is very common. EDM removes material at rates of 0.5 in^3 per minute with +/- 0.5 mil tolerances. ECM can remove 1 in^3 per minute at 10 kA. Electrochemical grinding is especially effective in producing ultra-fine finishes on molybdenum.
Q: After we do some assembly operations we would like to bend molybdenum sheets. Is it possible?
A: Sheets under 0.5 mm can usually take a 180 deg bend at room temperature. Thicker material must be heated in order to bend. If forming heavy plate, red heat may be required. Dies and tools can be warmed with infrared lamps or strip heaters to assist the bending process. Contact Bill or Ken at Torrey Hills in San Diego for more information about heaters or text your question to 415.890.3022
Q: What temperature is used for placing molybdenum rivets?
A: The section size regulates the proper temperature but 400 to 1400 deg F is the range. Furnace shields sometimes employ laced molybdenum wires.
Q: What is a good coolant that does not contaminate molybdenum?
A: A 50/50 mixture of chlorinated cutting oil and trichlorethylene.
Q: What is a popular way to clean molybdenum?
A: One popular technique is to immerse the material in a glass cleaning etch composed of:
95% H2SO4
4.5% HNO4
0.5% HF and CRO
(equivalent to 18. gm/l)
Another option is as such:
First, immerse material in an alkaline bath composed of...
10% NaOH
5%KMnO4
85% H2O
The temperature of the bath should be kept between 150-180 deg F (66-82 deg C) with a soak duration of 5-10 mins.
Subsequently, a second bath must be used to remove possible smut: 15% H2SO4
15% HCl
70% H2O
6-10 wt % per unit volume of chromic acid
The second bath has the same soak requirement as the first bath.
Q: Are there are any ways to clean TZM?
A: Here are the steps:
Degrease the material for 10 minutes in a solvent
Immerse in a commercial alkaline cleaner, 2-3 mins.
Rinse in cold water
Buff and vapor blast
Re-immerse in alkaline cleaner as above
Rinse in cold water
Electropolish in 80% H2SO4 at 120 deg F (54 deg C) with 8-12 amps.
Repeat the process beginning with the first rinse
Q: How to determine molybdenum's chemical reactivity traits?
A: See this reference material below:
Molybdenum's Chemical Reactivity Traits
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R | VR | NR |
|
R | VR | NR |
| Water | X | Hydrogen | X | ||||
| HF Acid (See Note 1) | X | Nitrogen | X | ||||
| Hydrochloric Acid (cold) | X | Inert Gases (all) | X | ||||
| Sulfuric Acid (hot) | X | Carbon Monoxide (1400 deg C) Carbide Formation | X | ||||
| Nitric Acid (cold) | X | Carbon Dioxide (1200 deg C) Oxidation | X | ||||
| Nitric Acid (hot) | X | Hydrocarbons (1100 deg C) Carbide Formation | X | ||||
| Aqua Regia (cold) | X | Aluminium (molten) | X | ||||
| Aqua Regia (hot) | X | Iron (molten) | X | ||||
| Nitric/Hydroflouric mixture (See Note 1) | X | Cobalt (molten) | X | ||||
| Aqueous Ammonia | X | Nickel (molten) | X | ||||
| Aqueous Caustic Soda/Potash | X | Tin (molten) | X | ||||
| Molten Caustic | X | Zinc (molten) | X | ||||
| Molten Caustics (See Note 2) | X | Lead | X | ||||
| Boron (hot) Boride Formation | X | Cesium | X | ||||
| Carbon (1100 deg C) Carbide Formation | X | Gallium | X | ||||
| Silicon (1000 deg C) Silicide Formation | X | Potassium | X | ||||
| Phosphorus | X | Lithium | X | ||||
| Sulfide Formation (440 deg C) | X | Magnesium | X | ||||
| Iodine | X | Sodium | X | ||||
| Bromine | X | Mercury | X | ||||
| Chlorine | X | Bismuth | X | ||||
| Flourine (r.t.) | X | KNO2, KNO3, KCLO3 (molten) | X | ||||
| Oxygen or air (400-600 deg C) | X | Molten Glass | X | ||||
| Oxygen or air (>600 deg C) | X | AL2O3, BeO, MgO, ThO2, ZrO2 (<1700 deg C) | X |
| Notes: | Key: | ||||||||||
|
1. May be either hot or cold. 2. Molten caustics are in the presence of KNO2, KNO3, KCLO3, PbO2. |
|
Q: How does the specific heat of molybdenum vary with temperature?
A: See Figure 3
Q: Does molybdenum's thermal conductivity change if the temperature changes?
A: Yes, molybdenum's thermal conductivity is variable according to temperature per Figure 4:
Last Update: 13 FEB 2015