MatWeb seaches - better materials for fencing parts

[PeterGustafsson]

Hi!


The "horrible fencing accident" got me searching, and I decided to post some materials with theoretical properties of interest as stock for fencing parts.

First, let us look at what we use now. I will chose a common carbon steel to model a non-FIE blade.

Bethlehem Steel ASTM A36, >3/4 to 1-1/2 in. thick, as-rolled steel plate
Subcategory: ASTM Steel; Carbon Steel; Ferrous Metal; Low Carbon Steel; Metal

Component Wt. %
C Max 0.25
Cu Min 0.02
Fe Min 98.04
Mn 0.8 - 1.2
P Max 0.04
S Max 0.05
Si Max 0.4

Material Notes:
A popular "workhorse" grade, it is used widely for various applications.

Information provided by Bethlehem Steel Corporation

Physical Properties Comments
Density 7.85 g/cc Typical of ASTM Steel

Mechanical Properties
Hardness, Brinell 119 - 159 based on conversion from tensile strength
Hardness, Rockwell B 67 - 83 based on conversion from tensile strength
Tensile Strength @ Break 400 - 552 MPa
Tensile Strength @ Yield Min 248 MPa
Elongation at Break Min 18 % in 8"

Carbon steels are cheap (compared with most other alloys) and are not really bad in any property that is necessary for all high-volume applications. That combination has made them popular in cases where there are no special needs, and money is the deciding factor.

Let us look at the properties of a FIE blade. I choose a #1 of the list of the 71 different Maraging steels, not knowing what the exact composition is. Its properties do not seem incompatible with a FIE blade.

AISI Grade 18Ni (200) Maraging Steel, Annealed
Subcategory: Ferrous Metal; Low Alloy Steel; Low Carbon Steel; Maraging Steel; Metal

Key Words: maraging steels, UNS K92810, ASTM A538 (A), ASTM A579 grade 71
Component Wt. %
Al 0.1
B 0.003
C Max 0.03
Co 8.5
Fe 69
Mn Max 0.1
Mo 3.25
Ni 18.5
P Max 0.01
S Max 0.01
Si Max 0.1
Ti 0.2
Zr 0.01

Material Notes:

Applications: Bearings, Belleville springs, bolts, cannon recoil springs, rocket motor and missiles cases, couplings, load cells, flexures for guidance mechanisms of missiles, helicopter drive shafts, transmission shafts, fan shafts in commercial jet engines, aircraft wing components and forgings, aluminum die casting dies, cold forming dies, plastic molding dies, cores, pins, punches, and trim knees.

Physical Properties Comments
Density 8 g/cc

Mechanical Properties
Hardness, Brinell 290
Hardness, Knoop 311
Hardness, Rockwell B 99
Hardness, Rockwell C 30
Hardness, Vickers 301
Tensile Strength, Ultimate 965 MPa
Tensile Strength, Yield 660 MPa
Elongation at Break 17 %
Reduction of Area 75 %
Modulus of Elasticity 183 GPa
Bulk Modulus 140 GPa
Poisson's Ratio 0.3
Shear Modulus 70 GPa Estimated from elastic modulus

Electrical Properties
Electrical Resistivity 1.74e-005 ohm-cm Typical steel

Thermal Properties
CTE, linear 500°C 10.1 µm/m-°C 21-480°C
Thermal Conductivity 25.3 W/m-K 20°C

A material which has a track record in applications where there are large deformations, and the component is expected to stay in the elastic range.

Now, let us go all-out to find a really high-end alloy. We want it to have reasonably similar density and elastic modulus to steels, in orde to keep the "feel" of the blade similar. OTOH, we want to have high elongation at break, in order to minimize the risk of the blade snapping. We also want it to have a high ultimate strength, so that any blade snapping requires large forces. We also want it to be chemically inert, so that we do not have to wory about blades rusting. A bit of searching gives us this candidate:

Haynes® 242™ alloy, hot rolled plate, annealed and aged, tested at RT
Subcategory: Metal; Nickel Base; Superalloy
Component Wt. %
Al Max 0.5
B Max 0.006
C Max 0.03
Co Max 2.5
Cr 7 - 9
Cu Max 0.5
Fe Max 2
Mn Max 0.8
Mo 24 - 26
Ni 58
Si Max 0.8

Material Notes:
Nickel content to balance. Age-hardenable, high ductility in the aged condition, lower thermal expansion than most alloys, very good oxidation resistance up to 815°C, excellent low cycle fatigue properties, very good thermal stability, and resistance to high-temperature fluorine and fluoride environments. Applications include seal rings, containment rings, duct segments, casings, fasteners, rocket nozzles, pumps, hydrofluoric acid vapor containing processes, fluoroelastomer process equipment such as extrusion screws.

Physical Properties Comments
Density 9.05 g/cc at RT

Mechanical Properties
Hardness, Brinell 257
Hardness, Knoop 286
Hardness, Rockwell C 19
Hardness, Vickers 271
Tensile Strength, Ultimate 1270 MPa
Tensile Strength, Yield 780 MPa at 0.2%
Elongation at Break 38.1 % in 4D
Reduction of Area 46.6 %
Modulus of Elasticity 229 GPa RT

Electrical Properties
Electrical Resistivity 0.000122 ohm-cm RT

Thermal Properties
CTE, linear 20°C 10.8 µm/m-°C 25-100°C
Specific Heat Capacity 0.386 J/g-°C RT
Thermal Conductivity 11.3 W/m-K RT
Melting Point 1290 - 1375 °C
Solidus 1290 °C
Liquidus 1375 °C
Maximum Service Temperature, Air 815 °C

Short translation for the non-engineers: A blade made of this stuff will outlive you, and probably your descendants. Anything short of a bolt cutter will not do anything to this puppy. If you try to use a cheap bolt cutter, be prepared to buy a replacement for it. Anything that can be used around hydroflouric acid vapor will not rust due to sweat.

OK then, the sabre fencers would like a lighter blade. Let's see what has a low density, high elongation at break, reasonably high elastic modulus, and no deal-breaking bad properties. A search of density<5g/cc, epsilonb>20%, and E>100GPa gives a list of 33 different Titanium alloys. Pure titanium has the by far highest elongation at break (54%), but it has lower fatigue properties than many of its alloys. The alloys with the 2nd highest elongation at break seems to be a good choice to start with:

TIMETAL® 35A CP Titanium (ASTM Grade 1)
Subcategory: Metal; Nonferrous Metal; Titanium Alloy; Unalloyed/Modified Titanium

Key Words: UNS R50250
Component Wt. %
C Max 0.08
Fe Max 0.2
H Max 0.015
N Max 0.03
O Max 0.18
Ti Min 99.1

Material Notes:
Titanium content above is calculated as the remainder and may not reflect the actual range.

Commercially Pure Titanium.

Industry Specifications: Germany Engineering: 3.7025. Germany Aerospace: 3.7024. France: T-35. UK Aerospace Specification: BS TA. 1.

Features: The mechanical properties of CP titanium are influenced by small additions of oxygen and iron. By careful control of these additions, the various grades of commercially pure titanium are produced to give properties suited to different applications. TIMETAL 35A contains the lowest oxygen and iron levels, producing the most formable grade of material. It has the highest purity, lowest strength, and best room-temperature ductility and formability of the four ASTM commercially pure grades. 35A should be used where maximum formability is required such as in explosive bonding and plate type heat exchangers. It exhibits excellent corrosion resistance in highly oxidizing to mildly reducing environments, including chlorides. It has good impact properties at low temperatures. In addition, TIMETAL 35A can be easily welded, machined, cold worked, hot worked, and cast. It is nonmagnetic.

Typical heat treatment for this alloy: Anneal at 700°C for 1 hour and air cool. Stress Relieve at 500°C for 30 mins and air cool.

Physical Properties Comments
Density 4.51 g/cc Typical

Mechanical Properties
Tensile Strength, Ultimate 345 MPa Typical
Tensile Strength, Yield 220 MPa Typical 0.2% Proof Stress
Tensile Strength, Yield 220 MPa Typical 0.2% Proof Stress
Elongation at Break 35 % Typical
Reduction of Area 70 % Typical
Modulus of Elasticity 105 - 120 GPa Typical
Fatigue Strength 123 MPa Notched, Kt=3; limit at 10^7 cycles; rotating bend
Fatigue Strength 193 MPa Smooth, Kt=1; limit at 10^7 cycles; rotating bend
Bend Radius, Minimum 2 t Typical; on 2 mm sheet

Electrical Properties
Electrical Resistivity 4.5e-005 ohm-cm

Thermal Properties
CTE, linear 20°C 8.6 µm/m-°C 20-100°C
Thermal Conductivity 21.97 W/m-K
Maximum Service Temperature, Air 425 °C Continuous

The low modulus of elasticity would mean that one would have to use larger cross-section dimension to maintain the stiffness requirement of a sabre blade. Combined with the relatively low hardness of the Ti alloys, one unintended consequence would be that if the tip hits the mask grid or the mask window, the maximum stresses to the latter two would be greatly reduced. The combination of a relatively low tensile strength (not much lower than that of ordinary blades, though) and a really high elongation at break would lead to a specific pattern in blade retirement: When sufficiently hard direct hits land, the blade will deform past its elastic limit. It will then deform plastically, but very rarely break. Sabre fencers would end up with bent blades with huge kinks in them - but no broken blades puncturing opponents. The blades would never rust.

Part two to follow, too long post!


Have a nice time!

Peter Gustafsson

[PeterGustafsson]

Hi!

Here comes the part that exceeded the 10000 characters limit.

Let us assume that the sabre fencer likes this light blade, but wants a high tensile strength at yield so that blades do not kink so often. He also wants a high fatigue strength, so that the blade will take forceful hits repeatedly. In order to get this, he is willing to sacrifice some of the elongation at break, but not to values considerably worse than those of usual steels. So, a seach with density<5g/cc, elongation at break>15%, Tensile strength at yield>500 MPa gives a list of list of 58 alloys, 57 of them Ti-based. A good choice is:

Titanium Ti-6Al-2Sn-2Zr-2Mo-2Cr-.25Si
Subcategory: Alpha/Beta Titanium Alloy; Metal; Nonferrous Metal; Titanium Alloy

Key Words: Ti-6-22-22-S
Component Wt. %
Al 6
Cr 2
Mo 2
Si 0.25
Sn 2
Ti 86
Zr 2

Material Notes:
Unspecified Heat Treatment. Alpha-Beta Alloy. Welding is not recommended.

Physical Properties Comments
Density 4.65 g/cc lb/in³

Mechanical Properties
Tensile Strength, Ultimate 1160 MPa
Tensile Strength, Yield 1070 MPa
Elongation at Break 18 %
Modulus of Elasticity 123 GPa In Tension
Compressive Yield Strength 1170 MPa
Compressive Modulus 125 GPa
Poisson's Ratio 0.33
Charpy Impact 20.3 J V-notch
Fatigue Strength 280 MPa 1E+7 cycles, Notched
Fatigue Strength 500 MPa Unnotched 10,000,000 Cycles
Shear Modulus 46 GPa

Electrical Properties
Electrical Resistivity 0.00016 ohm-cm Estimated from similar materials

Thermal Properties
CTE, linear 20°C 9.4 µm/m-°C After alpha/beta treatment + age; 20-100ºC
Specific Heat Capacity 0.5 J/g-°C Estimated from similar materials
Thermal Conductivity 7.8 W/m-K Estimated from similar materials
Melting Point Max 1650 °C Liquidus; Estimated from similar materials

In short: this alloy is 40%lighter than steel. Its ultimate tensile strength is 20% better than maraging steel, and the tensile strength at yield is 62% better. The elongation at break is about the same. The fatigue strength, even when tested in a notched specimen for 10 million cycles, is really high. When testing in unnotched state, which is the one relevant to the blade bending case, its fatigue strength after 10 million load cycles is not much lower than the stress needed to deform a maraging steel to yield - in one load cycle. For comparison: FIE specifies that epee blades should survive a fatigue test to 17 thousand load cycles to be certified.

So, there are better materials out there, if one is prepared to do the job. Prices? That is hard to say, but the last I found was that titanium and vanadium are in the 5-10$/pound price range, if you buy raw material at bulk amounts. I once found a price for a Ti/V alloy bar, long and thick enough to fit an epee blade in it. That bar cost some 70-80 $, if you were a company with an account with that metals retailer. Add in the machining, sales, profit together with various one-time costs to get a reasonable price estimate.


Have a nice time!

Peter Gustafsson

[Mergs]

Very impressive, Peter, but as you said in the last paragraph, the cost of processing added to the cost of the blade would be prohibative. One thing the MatWeb information didn't contain was any information on how well the material can be forged, machined, or welded, all processes currently used to manufacture blades. Ti/V is capable of all three, but in the case of welding, requires a very specialized process that I don't think any of the current blade manufacturers will be willing to invest in.

Also, Ti/V availability right now is very tight, and projections for the next 5 - 10 years look like it will get tighter.

[erooMynohtnA]

While I'm pessimistic about the future of superblades, I really enjoyed your post. Thanks a lot.

[mrbiggs]

I didn't understand most of the technical terms, but did you mention flexibility? If a blade can't be made to pass current flexability tests, it won't work.

[PeterGustafsson]

Hi!

I didn't understand most of the technical terms, but did you mention flexibility? If a blade can't be made to pass current flexability tests, it won't work.

The flexibility, as measured as the deflection in a gabarit, depends on two blade parameters:
1. The elastic (Young's) Moduli of the blade material. This figure is listed for all materials above, a typical value for most iron-based alloys would be around 200 GigaPascals.
2. The cross-sectional dimensions, or more exactly the area moment of inertia, of the blade and the distribution along the blade thereof.

If one chooses a material with a lower elastic modulus one has to have a higher area moment of inertia. However, since the area moment of inertia is proportional to the fourth power of the linear cross-section dimensions, the blade must not be all that much thicker. For example: Titanium (the 2nd alloy) has an elastic modulus of 123 GPa, while Maraging steel has an elastic modulus of 183 GPa. So, titanium has an E-value 67% of that of Maraging. To counteract this, the titanium blade must be 10.4% thicker and wider to have the same flexibility value.

This is not exactly difficult engineering, just look up any engineering mechanics coursebook intended for 1-2nd year of university-level mechanical engineering students. Any of the mechanics books by Stephen Timoshenko should suffice.


Have a nice time!

Peter Gustafsson

[counterattack]

Very impressive, Peter, but as you said in the last paragraph, the cost of processing added to the cost of the blade would be prohibative. One thing the MatWeb information didn't contain was any information on how well the material can be forged, machined, or welded, all processes currently used to manufacture blades. Ti/V is capable of all three, but in the case of welding, requires a very specialized process that I don't think any of the current blade manufacturers will be willing to invest in.

Also, Ti/V availability right now is very tight, and projections for the next 5 - 10 years look like it will get tighter.

Since this thread was recently linked and I missed it the first time around, I figured I'd resurrect it. Given the current costs of weapons, some of us would be willing to pay $500 for a super weapon. I wonder if they could be made for that. I break more than 10 FIE weapons a season, Lord only knows how many non-FIE I'd break. But I'll know at the end of the season since I am testing the received wisdom that "FIE are worth it since you break fewer".

It think it would take a new manufacturer to bring this to market, since old manufacturers have way too much at stake in the break-it-and-then-replace-it cycle. Also, the barrel would need to be correspondingly upgraded to make it most useful.

Currently welding is used to attach the tang. Is that necessary? I am actually pretty much in the dark about how the blades are currently forged and shaped. Anyone know much about it and care to share?

-ph

[Nolano]

Peter, the material you select at first is plain ol' non alloy hot rolled mild steel. not suitable for blades of knives, fencing weapons, or otherwise. Not to mention it's a very inconsistant material. I would expect a fencing blade to be made with steel consisting of at least .6% carbon, not to mention being a specific alloy rather than A36 which is basically all the low carbon scrap they've accumulated being melted down to be used. So really, nothing specific.

The maraging steel sample you specified is annealled, meaning it's as soft as it's going to get. Any blade you get is going to be either normalized or heat treated.
Also, I think the blades are made of a stronger alloy, anyways.

Not to mention that a big part of why maraging steel is used is because it slows crack propogation.

I'll look more later. Sleep is necessary for the time I get up.

[Telemakhos]

in one of these, you highlighted low-cycle fatigue. It seems to me that high-cycle fatigue might be a more appropriate category to investigate. Also, electrical resistivity would be something to take into account with all of these.

[Nolano]

Low cycle fatigue I believe refers to the amount of fatigue resulting from cycles, and not having a low amount of cycles before it fatigues.

[griffindm]

Anything looking promising with amorphous metal alloys (AKA "liquidmetals") for fencing blades?

[DHCJr]

I agree with Nolano about your selection.

Just because a steel is maraging does not mean it is legal for fencing blades.

For example the Nickel content is too high and the Cromium is too low to be legal.

[Cookeit]

Is it possible to make your blade into a huge magnet to make binds easier?

[Nolano]

I agree with Nolano about your selection.

Just because a steel is maraging does not mean it is legal for fencing blades.

For example the Nickel content is too high and the Cromium is too low to be legal.

Is there a specifications sheet with this information somewhere? I was just going off the properties of the metal, if there's something that says what is or isn't legal that would be cool.

[Mergs]

Is there a specifications sheet with this information somewhere? I was just going off the properties of the metal, if there's something that says what is or isn't legal that would be cool.

Check out the rule book. The chemical compositions are listed there.

[SJCFU#2]

Check out the rule book. The chemical compositions are listed there.

Specifically, Appendix A to the Material Section, Section 1, paragraph 3.2.

[DHCJr]

Thank you Mergs & SJCFU#2 for answering that.

I was tired when I posted.

[Nolano]

Ah. I checked, I guess I looked in the wrong place.
Thanks.