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Molybdenum and Molybdenum Alloys

Physical Properties of Molybdenum

Property Atomic Number 42

Atomic Weight 95.94Density 2!"# $!.22 g%&&Melting Point 2'9( ) 2($!"&* 4+5,"-moiling Point 49$2/* 55(!"&* ','2"-&oe0cient of 1hermal 3pansion 2!"# 4.9 3 $!(#%"&lectrical esisti6ity 2!"# 5.+ microhmscmlectrical &onducti6ity ,!7 8A&peci:c ;eat .!($ cal%g%"&1hermal &onducti6ity .,5 cal%cm2#%cm"&%secModulus of lasticity 2!"# 4( 3 $!(# psi

1?=M Molybdenum 997 M

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Pressed and sintered or recrystallized molybdenum machines very similarly tomedium hard cast iron. Wrought molybdenum machines very similarly to stainlesssteel. Molybdenum can be machined with conventional tools and equipment.However there are some ways that molybdenum difers rom medium hard cast ironor cold rolled steel:

t has a tendency to brea! out on the edges when cutting tools become dull

t is very abrasive. "his causes tools to wear much quic!er than steel

&orrosion esistance

Molybdenum corrosion resistance is very similar to tungsten. Molybdenum especiallyresists non#o$idizing mineral acids. t%s relatively inert to carbon dio$ide& ammoniaand nitrogen to ''(( ) and also in reducing atmospheres containing hydrogensul*de. Molybdenum has e$cellent resistance to corrosion rom iodine vapor&bromine& and chlorine& up to clearly de*ned limits. t also ofers e$cellent resistanceto some liquid metals including lithium& bismuth& sodium and potassium.

1urning and Milling

+or inside and outside turning& tools should be ground to angles and ra!es similar towhat is used or cast iron. ,peeds up to -(( eet per minute& with a depth o cut upto '/0& are *ne or rough turning. "he eed should be .('1 i.p.r. +or *nishing wor!&speeds tsp to 2(( eet per minute& with a depth cut o .((10 to .('10& and a eed o .((10 to .('(0 should be used. t is e$tremely important& when turning& that the deptho the cut always be greater than .((10. the depth is less& tool wear will bee$cessive. ,ulphur based cutting oil may be used as a lubricant or roughing cuts&and !erosene 3r sulphur base cutting oil can be used or *nishing wor!. lubricantsare not used tool wear will be e$cessive. ,ulphur base oils cannot be used orelectronic parts. )hlorinated oil and solvents are e$cellent as a machining lubricant.Molybdenum tends to chip when being machined so care must be ta!en to prevent

this. Wor! should be tightly chuc!ed& tools rigidly supported and machines should besu4ciently strong and ree rom chatter or bac!lash. Plenty o coolant is essential.+ace milling in general is not recommended. However& it can be done whennecessary. )arbide tipped cutters muse be used. "he speeds and depth o the cutshould be similar to those used in lathe turning& e$cept that the depth o cut shouldnot e$ceed .(1(0. Molybdenum plates can be edge machined. t is recommendedthat plates greater than .(1(0 should be edge machined 5ather than sheared to your*nished dimensions. "his can be done either on a shaper or a milling machine& andthe machining should be done along the edge& rather than across the edge. "hemolybdenum should he clasped between steel plates while being machined to avoidchipping.

6rilling& "apping and "hreading

Molybdenum can be drilled with high speed steel drills. However& carbide drills arerecommended or deep drilling. When using high speed steel drills& the speed shouldbe 7( to 1( eet per minute with a eed o .((7 i.p.r. )utting oils should be used orall tapping& drilling and threading operations. When threading the thread depthshould not be more than 1( to 8( percent because molybdenum tends to chip&Molybdenum can be rolled treaded. "he molybdenum material and the die should beheated to appro$imately 7-1 degrees +. Molybdenum can be heated to 7-1 degrees +in air without the danger o o$idation. However& molybdenum must not he heated totemperatures above 1(( degrees + e$cept in hydrogen or other protective

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atmospheres.

,awing

Molybdenum saws easily with power bend saws and hac!saws. 9ppro$imately '/0should be allowed or !er end 7'80 or the camber o heavier sections. Molybdenum

may also be abrasive saw cut. "he most efective blades are high speed steel withonly the tooth area hardened.

6M ; )M

min and ?# .(((10 tolerances have been achieved with 6M.6M wire cutting is used or intricate shapes. lectrochemical machining is normallycapable o appro$imately ' in=7> min stoc! removal at '(&((( amps. )M isespeciallyfective or producing ultra#*ne *nishes.