Refractory Metal Technical Data

Refractory Metals: Typical Analysis

Element	Maximum % Molybdenum	Maximum % Tungsten	Maximum % Tantalum	Maximum % Niobium
Aluminum	0.001	0.002	---	0.005
Calcium	0.003	0.003	---	---
Chromium	0.005	0.002	---	---
Copper	0.001	0.002	---	---
Iron	0.005	0.003	0.010	0.01
Lead	0.002	0.002	---	---
Magnesium	0.001	0.002	---	---
Molybdenum	99.95 Min	---	0.010	0.01
Manganese	0.001	0.002	---	---
Nickel	0.001	0.003	0.005	0.005
Silicon	0.003	0.002	0.005	0.005
Tin	0.003	0.002	---	---
Titanium	0.002	0.002	0.005	---
Tantalum	---	---	99.90 Min	0.2
Tungsten	---	99.95 Min	0.030	0.05
Carbon	0.005	0.005	0.0075	0.01
Oxygen	---	---	0.020	0.025
Nitrogen	---	---	0.0075	0.01
Hydrogen	---	---	0.0001	0.0015
Niobium	---	---	0.050	99.9

Typical Properties of Molybdenum, Tantalum, Tungsten

Ranges only: Data will vary with type of sample and previous work history

		Molybdenum	Tungsten	Tantalum
Property	Atomic Number	42	74	73
	Atomic Weight	95.95	183.86	180.95
	Atomic Volume	9.41	9.53	10.90
	Lattice Type	Body centered cube	Body centered cube	Body centered cube
	Lattice Constant; 20°C, A	3.1468	3.1585	3.3026
	Isotope (Natural)	92, 94, 95, 96, 97, 98, 100	180, 182, 183, 184 186	181
Mass	Density at 20° C gm/cc	10.2	19.3	16.6
Mass	Density at 20° C lb/in 3	0.368	0.697	0.600
Thermal Properties	Melting Point, °C	2610	3410	2996
	Boiling Point, °C	5560	5900	6100
	Linear Coefficient of Expansion per °C	4.9 x 10-6	4.3 x 10-6	6.5 x 10-6
	Thermal Conductivity at 20°C, cal/cm2/cm°C/sec.	0.35	0.40	0.130
	Specific Heat, cal/g/°C; 20°C	0.061	0.032	0.036
Electrical Properties	Conductivity, % IACS	30%	31%	13%
	Resistivity, microhms-cm; 20°C	5.7	5.5	13.5
	Temperature Coefficient of Resistivity per °C (0-100°C)	0.0046	0.0046	0.0038
Mechanical Properties	Tensile Strength at room temperature, psi	100,000-200,000	100,000-500,000	35,000-70,000
	Tensile Strength-500°C psi	35,000-65,000	75,000-200,000	25,000-45,000
	Tensile Strength-1000°C psi	20,000-30,000	50,000-75,000	13,000-17,000
	Young's Modulus of Elasticity; lb/in2
	Room Temperature	46 x 106	59 x 106	27 x 106
	500°C	41 x 106	55 x 106	25 x 106
	1000°C	39 x 106	50 x 106	22 x 106
Spectral Emissivity	(Wave Length approx. 0.65)	0.37 (1000°C)	0.45 (900°C)	0.46 (900°C)
Working Temperature		1600°C	1700°C	Room
Recrystallizing Temp		900-1200°C	1200-1400°C	1000-1250°C
Stress Relieving Temp		800°C	1100°C	850°C
Metallography	Etchant	Hot H2O2; 6% sol	HF-NH; F sol	Alk.K3FE(CN) sol
Metallography	Polishing	Alumina - Rouge to finish

Note: Etch and polish repeatedly until grain boundaries appear.

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Data on Molybdenum

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Data on Molybdenum and Tungsten

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Chemical Reactivity of Molybdenum

R = Resistant. VR = Variable Resistance depending on temperature and concentration. NR = Non-resistant.

Reagent	R	VR	NR
Water	X
Hydroflouric Acid1	X
Hydrochloric Acid (cold)	X
Sulfuric Acid (hot)		X
Nitric Acid (cold)		X
Nitric Acid (hot)			X
Aqua Regia (cold)		X
Aqua Regia (hot)			X
Nitric/Hydroflouric mixture1			X
Aqueous Ammonia		X
Aqueous Caustic Soda/Potash	X
Molten Caustic		X
Molten Caustics2			X
Boron (hot)-Boride fomation			X
Carbon (1100°C)-Carbide Formation			X
Silicon (1000°C)-Silicide Formation			X
Phosphorous	X
Sulfide Formation (440°C)			X
Iodine	X
Bromine	X
Chlorine	X
Flourine (room temperature)			X
Oxygen or air (>400°C)		X
Oxygen or air (>600°C)			X

Reagent	R	VR	NR
Hydrogen	X
Nitrogen	X
Inert Gasses (all)	X
Carbon Monoxide (1400°C)-Carbide Formation			X
Carbon Dioxide (1200°C)-Oxidation			X
Hydrocarbons (1100°C)-Carbide Formation			X
Aluminum (molten)			X
Iron (molten)			X
Cobalt (molten)			X
Nickel (molten)			X
Tin (molten)			X
Zinc (molten)		X
Lead		X
Cesium		X
Gallium		X
Potassium		X
Lithium		X
Magnesium		X
Sodium		X
Mercury		X
Bismuth	X
KNO2, KNO3, KCLO3 (molten)			X
Molten Glass	X
Al2O3, BeO, MgO, ThO2, ZrO2(<1700°C)	X

Notes: May be either hot or cold or Molten Caustics are in the presence of KNO2, KNO3, KCLO3, PbO2.

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Chemical Reactivity of Tungsten

R = Resistant. VR = Variable Resistance depending on temperature and concentration. NR = Non-resistant.

Reagent	R	VR	NR
Water	X
Water Vapor (red heat)-Oxidation			X
Hydroflouric Acid	X
Hydrochloric Acid	X
Sulfuric Acid		X
Nitric Acid	X
Aqua Regia (cold)	X
Aqua Regia (warm/hot)			X
Nitric/Hydroflouric mixture			X
Aqueous Caustic Soda/Potash	X
Ammonia	X
Ammonia in presence of H2O2		X
Ammonia (<700°C)	X
Ammonia (>700°C)		X
Carbon (>1400°C)-Carbide Formation			X
Iodine (at red heat)			X
Bromine (at red heat)			X
Chlorine (>250°C)		X
Carbon Disulfide (red heat)			X
Mercury (and vapor)	X

Reagent	R	VR	NR
Flourine			X
Oxygen or air (<400°C)	X
Oxygen or air (>400°C)		X
In air		X
Hydrogen	X
Nitrogen	X
Carbon Monoxide (<800°C)	X
Carbon Monoxide (>800°C)		X
Carbon Dioxide (>1200°C)-Oxidation			X
Aluminum oxide-Oxidation			X
Magnesium Oxide-Oxidation			X
Thorium oxide (>2220°C)-Oxidation			X
Sodium Nitrite (molten)			X
Sulfur (molten, boiling)		X
Hydrogen/Chloride Gas (<600°C)	X
Nitric Oxide (hot)-Oxidation			X
Hydrogen Sulfide (red heat)		X
Sulfur Dioxide (red heat)			X
In presence of KNO2, KNO3, KCLO3, PbO2			X

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Chemical Reactivity of Tantalum

R = Resistant. VR = Variable Resistance depending on temperature and concentration. NR = Non-resistant.

Reagent	R	VR	NR
Acetic Acid	X
Acetic Anhydride	X
Aluminum Chloride	X
Aluminum Sulfate	X
Ammonia		X
Ammonium Chloride	X
Ammonium Hydroxide		X
Ammonium Nitrate	X
Ammonium Phosphate	X
Ammonium Sulfate	X
Amyl Acetate or Chloride	X
Aqua Regia	X
Arsenic Acid	X
Barium Hydroxide	X
Bromine, dry (<200°C)	X
Calcium Hydroxide	X
Calcium Hypochlorite	X
Chlorinated Brine	X
Chlor. Hydrocarbons	X
Chlorine, dry (<175°C)	X
Chlorine, wet	X
Chlorine Oxides	X
Chloracetic Acid	X
Chromic Acid	X
Chrome Plating Solutions	X
Cleaning Solution	X
Copper Salts	X
Ethylene Dibromide	X
Ethyl Chloride	X
Fatty Acids	X
Ferric Chloride	X
Ferric Sulfate	X
Ferrous Sulfate	X
Flourine			X
Formic Acid	X
Fuming Nitric Acid	X
Fuming Sulfuric Acid			X
Hydrobromic Acid	X
Hydrochloric Acid	X
Hydrocyanic Acid	X
Hydrofluoric Acid			X
Hydrogen Bromide	X
Hydrogen Chloride	X
Hydrogen Iodide	X
Hydrogen Peroxide	X
Hydrogen Sulfide	X
Hypochlorous Acid	X
Iodine (<1000°C)	X
Lactic Acid	X
Magnesium Chloride	X
Magnesium Sulfate	X
Mercuric Chloride	X

Reagent	R	VR	NR
Methyl Sulfuric Acid	X
Nickel Chloride	X
Nickel Sulfate	X
Nitric Acid	X
Nitric Acid, fuming	X
Nitric Oxides	X
Nitrous Acid	X
Nitrosyl Chloride	X
Organic Chloride	X
Oxalic Acid	X
Perchloric Acid	X
Phenol	X
Phosphoric Acid <4ppmF	X
Pickling Acids1	X
Phthalic Anyhydride	X
Potassium Carbonate		X
Potassium Chloride	X
Potassium Dichromate	X
Potassium Hydroxide2		X
Potassium Hydroxide3			X
Potassium Iodide-Iodine	X
Silver Nitrate	X
Sodium Bisulfate, molten			X
Sodium Bisulfate, solution	X
Sodium Bromide	X
Sodium Carbonate		X
Sodium Chlorate	X
Sodium Chloride	X
Sodium Hydroxide2		X
Sodium Hydroxide3			X
Sodium Hypochlorite	X
Sodium Nitrate	X
Sodium Sulfate	X
Sodium Sulfide		X
Sodium Sulfite	X
Stannic Chloride	X
Sulfur (<500°C)	X
Sulfur Dioxide	X
Sulfur Trioxide			X
Sulfuric Acid (>160°C)	X
Zinc Chloride	X
Zinc Sulfate	X
Liquid Metals
Bismuth (<900°C)	X
Gallium (<450°C)	X
Lead (<1000°C)	X
Lithium (<1000°C)	X
Magnesium (<1150°C)	X
Mercury (<600°C)	X
Sodium (<1000°C)	X
Sodium - Potassium Alloys (<1000°C)	X
Zinc (<500°C)	X

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Comparative Machinability Ratings of Some Refractory Metals and Other Difficult Materials

				Carbide Tool				Machinability Ratings
Workpiece Material	Hardness	Surface Speed (ft/min)	Cut Depth (in.)	Feed (in/rev)	Type	Life (in3)	Removal Rate (in3/min)	Relative Removal Rate	Relative Removal Cost
Steel
4130	200 BHN	445	0.12	0.019	C6	582	11.50	100.0	1
4130	54RC	90	0.12	0.004	C6	19	0.62	5.4	19
*Superalloys*
Rene 41	320 BHN	70	0.06	0.009	C2	23	0.47	4.1	25
Rene 41	365 BHN	70	0.06	0.009	C2	16	0.47	4.1	25
Refractory Metals
TZM	217 BHN	350	0.06	0.009	C2	99	2.30	20.0	5
Niobium	112 BHN	300	0.12	0.005	C2	151	2.20	19.0	6
Unalloyed, Wrought Molybdenum	223 BHN	275	0.10	0.010	C1	132	3.30	29.0	4

Note:
Ratings based on metal removal rate for 4130 steel at 100,000 psi tensile strength as 100; lower numbers indicates poorer machinability.

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Vacuum Furnaces

In the cold wall vacuum furnace design, heating is from within the vacuum vessel so the heat losses from the work area to the cold wall must be reduced. To be compatible with the vacuum system, the insulation must meet certain requirements. These include:

low absorption
absorption
cleanliness; the material must not be prone to dusting which could be injurious to the vacuum pumps.
low heat storage to facilitate cooling
light weight
high strength

Molybdenum is an ideal material for this application. Rembar stocks all the materials normally used in vacuum furnaces and can do much of the fabrication of both new and replacement parts. There are three basic insulation systems that will meet most of the above requirements. These systems can be classified as:

Shield Pack
a series of non-contacting metal sheets.
Insulation Pack
an inner metallic shield supporting a blanket insulation against a metallic outer shell.
Self-facing Insulation
such as rigidized alumina-silica fibers and graphite felt.

The shield pack insulation system is composed of a multi-layer design that is made up of metal sheets that are separated to form a series of reflective shields. The selection of shield material is dependent on the maximum use-temperature of the system. Most commonly used is molybdenum.

The advantage of Radiant Molybdenum Shielding over other materials is:

Cleanliness
Molybdenum will not flake off particles that could contaminate the work or pumping system.
Heat
Heat absorption of molybdenum is reflective to the radiant energy. This is the only way that heat can be transferred in a vacuum.
Outgassing
Molybdenum does not absorb gases as do the other materials. Therefore it does not outgas them during heat up to avoid prolonged pump down times.
Low Heat Storage
Molybdenum does not hold temperatures as long as the other materials and, therefore, allows for faster cooling.

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Radiant Shield Data for Molybdenum

Furnace Temperature, x F	1832	1832	2012	2012	2400	2400
Cold Shell Temperature, x F	100	100	100	100	100	100
Number of Shields (1 - 10)	1	2	1	2	1	2
Avg. Shield Emissivity Factor (0 - 1.0)	0.60	0.60	0.60	0.60	0.60	0.60
Cold Shell Emissivity Factor (.9 typ)	0.90	0.90	0.90	0.90	0.90	0.90

Computed Shield Temperature IN x F
#1 Shield	1484	1646	1637	1811	1965	2167
#2 Shield		1250		1384		1672
Computed Heat Loss (KW/ft2)	4.0	2.4	5.5	3.3	9.8	5.9
Furnace Temperature, x F	2400	2400	2400	2400	2192	2192
Cold Shell Temperature, x F	150	150	150	150	100	100
Number of Shields (1 - 10)	3	4	5	6	1	2
Avg. Shield Emissivity Factor (0 - 1.0)	0.60	0.60	0.60	0.60	0.60	0.60
Cold Shell Emissivity Factor (.9 typ)	0.70	0.70	0.70	0.70	0.90	0.90

Computed Shield Temperature IN x F
#1 Shield	2247	2282	2305	2320	1789	1976
#2 Shield	1976	2087	2151	2194		1517
#3 Shield	1563	1832	1966	2047
#4 Shield		1444	1723	1869
#5 Shield			1354	1636
#6 Shield				1282

Computed Heat Loss (KW/ft2)

4.0

3.1

2.6

2.2

7.3

4.3

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Machining and Welding Nickel-Iron Alloys

(ASTM F-15 and Similar Alloys)

In general, these alloys are not difficult to machine, provided it is noted that these materials work-harden readily. Also note that adequate care is taken on the choice of such factors as tool geometry and material, speeds, feeds, cutting fluids, etc. The following data is intended as a guide to proper selection of these parameters for machining Ni-Fe alloys.

General Machining

Maximum rigidity of tool and workpiece must be obtained to insure smooth cutting.
Machine speed should be kept low enough to provide sufficient torque or force at the cutting edge to prevent deceleration.
Tools must be kept sharp with a high degree of surface finish on the rake face.
Tool material should be either high speed steel or tungsten carbide.

Cutting Fluids

A large amount of heat is generated in cutting this material. Consequently, machining is made easier by using a good cutting fluid.

For general machine work, a copious flow (approximately 1 gpm/HP used) of soluble oil is recommended. A chlorinated oil is suggested for use on automatic and semi-automatic machines where a neat oil is required.

Turning and Boring

The general set up for these operations is similar to that used for steel. The following principle should be adhered to as closely as possible.

It is preferable to take a deep cut with a light feed rather than a light cut with a heavy feed.
Tool relief angles should be kept to a minimum in order to provide maximum support for the cutting edge.
To insure adequate chip disposal when roughing, it may be necessary to vary the values for back or side rake angles slightly. This is to have the chip curl over and break on the workpiece in advance of the tool.

The following tool geometry, speed and feed values are given as a general guide for use with tungsten carbide tools. The speed and feed figures should generally be reduced by approximately 30% for high-speed steel tools.

Detail	Roughing Value	Finishing Value
Back rake angle	8°	10°
Side rake angle	3°	8°
Front cutting edge clearance angle	3°	3°
Slide cutting edge clearance angle	3°	3°
Plan trail angle	8°	5°
Plan approach angle*	15°	20°
Nose radius	0.30 in (0.8 mm)	0.05 in (1.3 mm)

Speed and Feeds	Roughing	Finishing
Depth of cut	0.1 in (2.5 mm)	<=0.010 in (0.25 mm)
Feed (in-mm/rev)	0.015 in (0.4 mm)	>=0.004 in (0.10 mm)
Speed (SFPM)	90	120

*Where it is impossible or impractical to apply this value, a decrease in plan approach angle should be followed by an increase in side rake and a decrease in back rake. Note that the secondary front cutting edge clearance angle should be to suit application.

Planing Techniques

To enable only a light cut to be taken with the finishing tool, roughing cuts should be taken to within approximately 0.25 in. (0.635 mm) of the finished dimension.

A goose neck type of planer tool is recommended for smoother finishing cuts since its shape enables it to withstand the greater mechanical shock encountered when machining Ni-Fe alloys.

The following tool angles are given as a general guide for use with high-speed tools.

Detail	Roughing Value	Finishing Value
Back rake angle	8°	10°-15°
Side rake angle	15°	8°
Front cutting edge clearange angle	4°	4°
Slide cutting edge clearance angle	4°	4°
Nose radius	0.125 in (3 mm)	0.250 in (6 mm)

Drilling

The following principles should be observed when drilling Ni-Fe alloys:

HSS twist drills with a high degree of flute finish should be used.
Drills should be reground as soon as they show signs of dulling.
A large amount of cutting fluid should flow onto the cutting edge of the drill.
When hand feeding, sufficient pressure should be applied to keep the cutting edge beneath the work surface to prevent work-hardening the material.
When drilling into a previously worked surface, it may be necessary to thin the drill web and increase the point angle from a nominal 118° to 150°.
Peripheral speeds should be of the order of 50 surface feet per minute with feeds not less than 0.004 in/rev (0.1 mm/rev).

Precision Grinding

The methods for grinding Ni-Fe alloys are similar to those used with steel. However, certain conditions require that a slightly softer grade of wheel be used to prevent loading the wheel. A copious flow of lubricant should be used.

Where high permeability is required, final grinding (after annealing) should finish with approximately five cuts progressively decreasing from 0.002 in (0.05 mm) to 0.0002 in (0.005 mm).

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Melting Points of Metals

High
	°C	°F
Tungsten	3410	6170
Rhenium	3180	5756
Tantalum	2996	5425
Osmium	2700	4892
Molybdenum	2610	4730
Iridium	2454	4449
Ruthenium	2450	4442
Niobium	2468	4379
Boron	2300	4172
Hafnium	2230	4046

Medium
	°C	°F
Rhodium	1966	3571
Chromium	1930	3506
Zirconium	1857	3375
Thorium	1845	3353
Platinum	1773	3223
Titanium	1725	3137
Vanadium	1710	3110
Palladium	1549	2820
Iron	1535	2795
Cobalt	1495	2723
Yttrium	1490	2714
Nickel	1455	2651
Erbium	1450	2642
Beryllium	1278	2332
Manganese	1220	2228
Europium	1150	2102
Uranium	1133	2071
Copper	1083	1981
Samarium	1072	1962
Gold	1063	1945
Silicon	1410	2570

Low
	°C	°F
Neodymium	1024	1875
Silver	961	1762
Germanium	947	1737
Lanthanum	920	1688
Barium	850	1562
Calcium	848	1558
Cerium	815	1499
Arsenic	814	1497
Strontium	774	1425
Aluminum	660	1220
Magnesium	651	1204
Antimony	630	1166
Tellurium	452	846
Zinc	419	786
Lead	327	621
Cadmium	321	610
Thallium	302	576
Bismuth	271	520
Tin	232	450
Selenium	217	423
Lithium	179	354
Indium	156	313
Sodium	98	208
Potassium	62	144
Gallium	30	8
Mercury	-38.8	-38

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Densities of Metals

High
	G/CC
Osmium	22.48
Iridium	22.42
Platinum	21.45
Rhenium	21.02
Gold	19.30
Tungsten	19.30
Uranium	19.05
Tantalum	16.60
Mercury	13.55
Hafnium	13.09
Rhodium	12.44
Ruthenium	12.20
Palladium	12.02
Thallium	11.85
Thorium	11.70
Lead	11.34
Silver	10.49
Molybdenum	10.20

Medium
	G/CC
Bismuth	9.90
Erbium	9.16
Copper	8.96
Cobalt	8.92
Nickel	8.90
Cadmium	8.65
Niobium	8.57
Iron	7.87
Manganese	7.44
Indium	7.31
Tin	7.30
Chromium	7.14
Zinc	7.14
Neodynium	7.00
Samarium	6.93
Cerium	6.78
Antimony	6.68
Zirconium	6.50
Tellurium	6.24
Lanthanum	6.19
Vanadium	6.11

Low
	G/CC
Gallium	5.97
Arsenic	5.73
Germainium	5.32
Europium	5.24
Selenium	4.81
Titanium	4.50
Yttrium	4.34
Barium	3.50
Aluminum	2.70
Strontium	2.60
Boron	2.34
Silicon	2.32
Beryllium	1.84
Magnesium	1.74
Calcium	1.55
Sodium	0.97
Potassium	0.86
Lithium	0.53

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Brazing Filler Metals for Refractory Metals

Brazing Filler Metal	Liquidus Temperature
Ag	1760°F	960°C
Cu	1980°F	1052°C
Ni	2650°F	1454°C
Pd-Mo	2860°F	1571°C
Pt-Mo	3225°F	1774°C
Ag-Cu-Mo	1435°F	779°C
Ni-Cu	2460°F	1349°C
Mo-Ru	3450°F	1899°C
Pd-Cu	2200°F	1204°C
Au-Cu	1625°F	885°C
Au-Ni	1740°F	949°C

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American Wire Gauge No. (AWG) to Inch/MM

Gauge No.	Inches	MM
7/0	0.651300	16.54
6/0	0.580049	14.73
5/0	0.516549	13.12
4/0	0.460000	11.68
3/0	0.409642	10.40
2/0	0.364797	9.266
1/0	0.324861	8.251
1	0.289297	7.348
2	0.257626	6.544
3	0.229423	5.827
4	0.204307	5.189
5	0.181941	4.621
6	0.162023	4.115
7	0.144285	3.665
8	0.128490	3.264
9	0.114424	2.906
10	0.101897	2.588
11	0.090742	2.305
12	0.080808	2.053
13	0.071962	1.828
14	0.064084	1.628
15	0.057068	1.450
16	0.050821	1.291
17	0.045257	1.150
18	0.040303	1.024
19	0.035891	0.9116
20	0.031961	0.8118
21	0.028462	0.7229
22	0.025347	0.6438
23	0.022572	0.5733
24	0.020101	0.5106
25	0.017900	0.4547
26	0.015941	0.4049
27	0.014196	0.3606
28	0.012641	0.3211
29	0.011258	0.2860
30	0.010025	0.2546
31	0.008928	0.2268
32	0.007950	0.2019
33	0.007080	0.1798
34	0.006305	0.1601
35	0.005615	0.1426
36	0.005000	0.1270
37	0.004453	0.1131
38	0.003965	0.1007
39	0.003531	0.08969
40	0.003145	0.07988
41	0.002800	0.07112
42	0.002494	0.06335
43	0.002221	0.05641
44	0.001978	0.05024
45	0.001761	0.04473
46	0.001568	0.03983
47	0.001397	0.03548
48	0.001244	0.03160
49	0.001108	0.02814
50	0.000986	0.02504
51	0.000878	0.02230
52	0.000782	0.01986
53	0.000697	0.01770
54	0.000620	0.01575
55	0.000552	0.01402
56	0.000492	0.01250
57	0.000438	0.01113
58	0.000390	0.00991
59	0.000347	0.00881
60	0.000309	0.00785

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