KVA Stainless Steel Bicycle Tubing

KVA Stainless processed martensitic stainless steel tubing is ideally suited for use in high-performance bicycle frame applications.

• Heat-treated to ultra-high strength: tensile strength > 200 ksi (1400 MPa)
• Air-hardening alloy, yet easy to fabricate (38-42 Rockwell C hardness)
• Best suited for silver-brazed or TIG welded construction
• "Feel of steel" - plus corrosion resistance gives excellent ride quality and durability
• Precision Made in U.S.A.

After years of engineering and development, KVA Stainless is introducing its new, patented, custom-made stainless steel bicycle tubing called MS² for high-performance bicycle frame applications.

Already proven by KVA Stainless in other industries, patented KVA martensitic stainless structural tubing can now be integrated into high performance bicycle frames to reduce weight, increase strength and stiffness, at a significant cost decreases over competitive materials. KVA Stainless controlled atmosphere thermal processing ensures consistent, high-quality tubing.

MS² is an air-hardenable, martensitic stainless steel with amazing tensile strength > 200 ksi (1400 Mpa) which means it’s twice as strong as titanium with a frame weight comparable to high-end aluminum. The tubing has excellent corrosion-resistance, with elongation > 14% and a hardness ~ 38-42 HRC.

MS² tubing is made in the U.S.A. from first quality domestic stainless steel alloys using the most modern forming, welding and precision thermal processing technology available to produce custom-made tubing; including variable wall thickness known as "butted" tubes.

You should expect excellent ride characteristics with outstanding durability and toughness from our new MS² bicycle tubing. Excellent mechanical properties, including specific strength and stiffness, toughness and fatigue performance, can be achieved using MS² tubing in place of other materials.

Ideal applications include silver brazed lugged construction and TIG welded bicycle frames.

Ed McCrink, the founder of KVA Stainless set up Hi-Temp, Inc. in 1953 and grew the company into one of the largest thermal processors of martensitic stainless steels in the United States. Successful with this venture, Mr. McCrink sold Hi-Temp in the 1970s and, with an entrepreneurial spirit, moved on to a number of different ventures. But Mr. McCrink couldn't forget about martensitic stainless steel. Mr. McCrink wondered why people weren't using this material in structural applications. Years after he sold the company, he came back to his roots of metallurgy, and he wanted to introduce the high strength features and benefits of martensitic stainless steel to different industries.

Working with a couple of engineers and metallurgists, Mr. McCrink developed a way to take flat sheets of martensitic stainless steel and transform them into tubes. Rolling the sheet to create the tube was never the hard part, welding a seam in martensitic steel so the tube became one solid structure or homogenous was always the issue. After years of engineering and testing, Mr. McCrink found a method to prevent the inherent cracking and weakness when a stainless steel tube is seam welded.

The resulting stainless tube is light and strong, and not nearly as expensive to produce as a seamless tube when compared to other stainless steel alloys or other metals, including titanium.

Bicycle Frame Materials

Strength, Safety, and Weight

In the hierarchy of cycling needs, cyclists care about weight, the feel of the ride, strength, and price.

Weight has been hyped in the media to the point that manufacturers are creating frames that are just one bad bump away from disaster. If you have not seen the results of failed forks and handlebars, try Googling "broken fork." It's not a pretty picture. The number of failures in high-end forks and frames is astounding, all because manufacturers feel pressure to defy the laws of physics with lighter and lighter forks and frames.

Safety is defined not just by the durability of a part, but also by the warnings the rider receives before component failure. A part that bends before it breaks is safer than one that snaps suddenly. Material strength equals safety, but what kind of strength?

Strength is measured in several ways, and it pays to consider all of them:

Impact Strength denotes how much concussive energy a component can absorb in a single blow without failing. Impact strength can be tested in a laboratory, but as a practical matter in cycling it is irrelevant. That’s because a severe impact will dislodge a rider long before it threatens the integrity of a frame or fork. Once the rider is down, the state of the part is meaningless.

Fatigue Strength is a measure of how well a material withstands repeated stress cycles. Fatigue strength is critical for a bicycle, since the rider constantly flexes a frame by pushing the pedals and pulling on the handlebars. Aluminum has the least fatigue strength among popular framebuilding materials. Steel, and Stainless Steel, by contrast, has the best... even exceeding that of titanium alloys. It can flex an infinite number of times below its "endurance limit" - a stress threshold for which no amount of cyclic loading will cause failure. This stress level is never approached simply by cycling on a properly designed and built steel (and stainless steel) frame.

Material (Fracture) Toughness is the feature of a material that describes its ability to prevent a nick from turning into a crack, and a crack from turning into a break. Toughness is another area where steel and Stainless Steel far outperforms aluminum, carbon fiber, and titanium. Think about it: When was the last time you saw carbon fiber nails, or aluminum rebar? Never.

Ultimate Tensile Strength (UTS) is a widely cited measurement of material strength. UTS is measured by pulling apart a test coupon made with material of a specific thickness and length. The UTS of tubing is not insignificant, but it is vastly overrated as a measurement of the strength. Bicycle frames are not torn in half, nor do they fail because of uniaxial tension. Other factors, such as fatigue, cracking, and impact will cause a frame to fail long before UTS becomes a factor. Glass has extremely high UTS because it is difficult to pull apart, but a glass bicycle would not last long on a mountain trail or even a street. All the materials used in traditional bicycle tubing have sufficient UTS to be safe.

The feature most critical to rider safety is its mode of failure. That is, how long the material will support the rider after its integrity has been breached by a crack, a hole, a dent, or even a deep scratch. A rapid–even instantaneous–failure is known as a catastrophic failure. Catastrophic failure leads to injury.

Of the most common materials used in bike frames today, carbon fiber has the highest rate of catastrophic failure. Steel and Stainless Steel has the lowest rate of catastrophic failure. When steel fails, it fails slowly. In a sport where speed is the name of the game, failure is the one area where it's good to be slow. Real slow.

Metals responds to force by bending, denting, and even stretching (elongation), not by snapping and shattering. The slow rate of failure provides time for the rider to pick up warning signals, feeling something is wrong prior to the failure of a component, preventing injury.

Of secondary importance, but worth considering, is reparability. The old auto body shop adage is “metal has memory.” Steel can be repaired more completely and more easily than other materials can.

Comparing frame materials that are new is one thing, but what about frame materials that have aged? Different materials age in different ways. Environmental factors such as temperature, humidity, air salinity, ozone, and ultraviolet radiation all affect framing material. Life is a laboratory that is constantly fizzing.

In the harsh world of chemical change, metals outlast plastics and carbon fiber. A weak point of carbon fiber is in the resins that hold the carbon fiber layers together. These resins are prone to degradation when exposed to ultraviolet light from the sun.

However, metals are not exempt from environmental degradation. Typical bicycle tubeset aluminum alloys, for example, "age" naturally to higher strengths over an extended period of time. While a stronger tube may appear better, the microstructural change robs the material of its ductility and can cause premature brittle failure – especially around welded joints.

The phrase "environmental degradation" often evokes images of metallic corrosion–rusted wheel wells, corroded hinges, and leaky watering cans. Rust (a term reserved for the corrosion byproduct of steel reacting with oxygen) actually builds up a protective layer that protects the underlying steel against further environmental damage. That is why it is not uncommon in some parts of the world to see 20-, 30-, even 40-year-old rust-covered steel-framed bikes still in use. Of course, the thicker the steel, the less vulnerable it is to failure due to corrosion. Super-thin, 0.35mm steel tube frames are more vulnerable to damage from rust than thicker-walled tubes are. However, diligent care with anti-rust, protective film sprays such as FrameSaver, Boesheild T9, and LPS can prevent corrosion. If you prefer old-school solutions, try coating the steel frame with linseed oil or automotive waxes. Alternatively, Stainless Steel tubing offers corrosion resistance as well as high strength. A "passive layer" of adherent chromium oxide forms to protect stainless steel from further environmental degradation. Under most conditions, this protective layer is self healing – if scratched new chromium oxide layer will form nearly instantaneously.

Another important, but rarely discussed, aspect of frame material is defect tolerance. No one wants to admit that materials have defects, but they do. It is impossible to manufacture quantities of anything without occasional defects. Even in the white-coated, "dust-free" environments, defects creep into materials. That’s why everyone from rocket engineers to computer chip manufacturers build defect tolerance and safety factors into their designs. Bicycle manufacturers should, too. The important thing to know is how an unseen defect will affect the strength and integrity of the material. A material that is more defect-tolerant is less likely to fail. Steel and Stainless Steel are materials that are highly defect-tolerant, due to their high toughness and durability. Carbon fiber is the least defect-tolerant of all materials used in the making of bicycle frames.

Shock absorption is another material quality that makes for a safer and smoother ride. The physics of shock absorption are as old as Newton's laws of motion: Every action causes and equal and opposite reaction. A shock is absorbed by motion–compression, deflection, or both, and dissipated within the material. Something has to give.

The idea that a shock can be absorbed without motion is a myth. One marketing claim is that carbon fiber forks absorb shocks well, creating a smoother, more comfortable ride. It sounds promising, but it conflicts with basic physics. Carbon fiber is very stiff, so there is relatively little movement to absorb the shock. Metal absorbs some shock through compression and deflection, but only suspension forks truly absorb shocks, because they move. Otherwise, the best way to create a smoother ride is to deflate your tires and lighten up on your grip.

Vibration damping is a phrase heard a lot in the cycling world, but its importance is exaggerated. The term refers to a material's tendency to absorb and dissipate vibrations after some force causes it to start vibrating. Wind chimes produce sustained vibration, pleasing their owners but often annoying the neighbors. Vibration is the result of high-frequency flex or applied loads. The flex of a component is influenced by the material it is made with, its size, and its shape.

The entire discussion of vibration damping is somewhat academic when it comes to cycling, however, since bicycle parts are not suspended in the air like a tuning fork. A bicycle is composed of multiple components, including the frame, the fork, rubber tires. Most importantly, a bicycle is in contact with the ground and it supports a rider whose body absorbs vibrations of the frame. Having said this, the bulk material properties can be used to generalize the "feel" of a frame and its tendency to damp vibrations. Carbon fiber, being very stiff (with a high elastic modulus) is considered by many to be harsh, transmitting every bump and ripple directly to the rider – causing fatigue and discomfort after long rides. Aluminum, magnesium and even titanium have been described as "soft and mushy", with their lower elastic modulus and stiffness. Riders enjoy the feel of steel and stainless steel – the resiliency and liveliness of the material is without comparison.

Physical comfort on a bicycle is influenced by several factors, of which frame materials is the least important. The height of the handlebars, the distance from the seat to the pedals, and the air pressure in the tires all contribute more to a comfortable ride than the frame materials do. Raise the handlebars, move the seat back, and decrease tire pressure for greater comfort. Remember to relax your body and lighten your grip, too.

Comfort is as much psychological as it is physical. A bike may fit your body perfectly, but if your mind is unsettled about it, it won't feel right. For example, a woman who grew up with an open "girls" frame might not ever feel comfortable on a standard diamond style frame. Similarly, hardcore racers who curled their 6-foot bodies around a 56cm frame might never get used to a 62cm frame, even if it is a better fit for their size. The same goes for frame materials. Steel affords the maximum strength and safety, but some people resist it on psychological grounds, mainly because of perceived weight penalties.

Consider this: The weight of the bicycle frame makes up only ¼ of the overall weight of a bicycle, and the bicycle is only 1/10 of the overall weight with a rider in place. In other words, frame weight is only 1/40 or 2.5 percent of the overall weight. So shaving a pound off the frame weight will change your overall weight by less than one percent. You can double that weight change simply by losing two pounds of body weight.

Many people believe engineering is more important than materials, but that is not entirely true. The differences in material–especially failure modes–can increase safety and reduce injuries. Steel and stainless steel frames may sound out of date, but for strength, safety, reparability, durability, and aesthetic beauty, nothing beats steel or Stainless Steel. Enjoy the Feel of Steel^TM

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