Bonzo Banana

I'm a little confused about different steels and wonder if someone could clarify it because it seems like there are often confusing ways steel is described for frames which seems inaccurate in bikes descriptions.

One thing that often seems confusing is you often read chromoly is better than high tensile steel but chromoly is a high tensile steel according to this wiki page and many other sites that list types of steels.

https://en.wikipedia.org/wiki/Carbon_steel

Also some chinese sites claim their high tensile steel frames have chromium and molybdenum but they still describe them as high tensile steel without mentioning chromoly. Brompton which describes their frames as high tensile steel but on their site also describe them as chromoly too.

Add to that some Chinese manufacturers sell 'high carbon steel frames' and claim these are superior to high tensile steel frames.

When a high tensile steel frame isn't using chromium and molybdenum what elements is it using instead, presumably these are the inferior high tensile steel frames?

Also dare I ask what is better high carbon steel for a frame or a high tensile steel?

It appears high carbon steel can be used for springs and wires and is very strong and can flex for many thousands of operations but is difficult to weld but modern robotic welding and other technology has improved welding of this material.

Where does modern high carbon steel frame manufacture rank compared to classic steels used in frames, better or worse? Is there any solid information out there that compares them for strength and durability?

Why have some of the higher quality steel frame manufacturers like fuji-ta moved from high tensile to high carbon steel for frames?

unterhausen

Without material properties, it's really hard to do anything but speculate.

koolerb

I'm guessing the ratios of chromium and molybdenum are what class some steels as chromoly. Hi-Ten is a pretty general term, the materials and ratios could vary quite a bit I imagine. I go to chromoly or a name brand product for sure. Not much help. I'm sure someone on the site will have some good detail on this.

Andrew R Stewart 

Without real alloy numbers, SAE designations, you are relying on the marketing departments to make the call. This will not be the last time word craft is used for a company's benefit. These words have a broad meaning to people and some will read into things what they hope for.


Steels use a number of elements to create the characteristics and cost they seek. Generally it's when an alloying element is added in a specific range of content (usually as in %) that the "new" alloy/steel gets a new designation. But some of an element might be present below the level to be called that next/new name. Enterprising ad men (and women) will use this to whatever advantage they can and still not get negative feedback.


An example of this was common during the late 1970s and early 1980s. Cro Moly (be it 4130 or 4140 or other) tubing decals were placed on the only tube that actually was "cro moly", the other tubes often being of lower cost steels. The consumer would see the decal and the spec list description of "cro moly frame" and assume that this meant all the tubes were what the decal said. Were the bike companies lying? Not really, but I sure had a number of customers who felt they were. after they were told of this practice.


Steels have been around for so many decades and have had so many people explore the possibilities of alloying that this stuff is pretty well figured out. Very few bike companies really describe their steel tubing with actual characteristics like elongation, Young's modulus, hardness. Instead they tend to use non specific terms as strength without further details. Remember many alloys of steel can vary their tensile strength with heat treating, for the better or worse and whether intended or as a result of the joining process. Andy

McBTC

Reynolds latest, bestest super-steel-- 953

Andrew R Stewart 

If you quote from a source other then already posted it would be nice to know where from it came. Not that the info is wrong...


Stainless steels are rather picky as to how they are dealt with in a fabricating sense. To maintain their potentials the construction needs to be controlled far more then with more common/lower cost/non SS steels. Even the emery cloth and files need to be segregated from those used on non SS steels.


This is exactly what I was referring to, "Steels use a number of elements to create the characteristics and cost they seek". These added construction needs makes a SS frame more costly, everything else being equal. Andy

Kontact

This is one of those situations where the bike industry terms don't accurately reflect the steel industry or metallurgical terminology. The same thing happens with knives because consumers don't really know what they are reading.

"Steel" is a term that means and alloy primarily of iron - usually with at least carbon (but not always). Chrome and molybdenum are common alloying elements in tools steels which make machining, forming, welding or heat treating easier. One of the most famous bike steels was 531, which was a manganese molybdenum steel instead of chrome. You could make a bike out of basic carbon steel, but forming tubes and joining them would be far more challenging. That's why low alloy hi-ten steel is "heavy" - since it doesn't have the nicer qualities of the better alloys it is produced with thicker tube walls to have similar strength to the tool steels.

There are essentially six types of steel used in bike frames today. Hi-ten, tool steels, heat treated tool steels, air hardening steels, stainless steel and precipitation hardening stainless steels.

As steels get more expensive they get stronger and more able to be flexed without fracturing or bending - despite welding or brazing temps. So they can be made with thinner tube walls and therefore lighter.


I would avoid trying to extract too much about metallurgy from the ad copy of a bicycle company. They aren't trying to deceive, but they are avoiding presenting confusing technical details.

Bonzo Banana

So what is high carbon steel and how does it fit into this line up of steels?

Materials and processes. - a Bike Culture article on Cyclorama

It doesn't appear to be mild steel according to this.

https://www.metalsupermarkets.co.uk/what-is-mild-steel/

Where does it fit in the picture of bicycle frames?

It seems to be producing quite light frames which are competitive with aluminium in weight sometimes. Is that because they have sacrificed strength?

Fuji-ta the worlds biggest bicycle manufacturer with maybe over 15 million complete bikes made a year and a huge business in selling frames to assemblers around Asia, Europe and the America's offers many high carbon steel frames even for higher end models be it racing, mountain bike etc but these seem to be models we don't really see in Europe so much where retailers favour aluminium especially mountain bikes. They claim they use an improved high carbon steel but on the site they still call it high tensile steel which is low carbon steel.

These high carbon steel frames seem to be typically lighter than the older high tensile steel frames of the past.

Looking around at tensile strength it looks like a typical old high tensile steel frame (1015 steel) had a high tensile strength of around 60,000 psi and a classic chromoly 4130 is 97,000 psi but the high carbon steels like 1065 is 92,000 psi which I suspect is after heat treatment as the high carbon steel frames are often heat treated. So would it be fair to put high carbon steel just below chromoly in pecking order or are there other factors?

The chinese seems to be promoting these high carbon steel frames as superior to older steel frames for their domestic market.

The aluminium frame materials 7005-T6 is at 51,000 psi tensile strength and 6061-T6 is at 45,000 obviously they are lighter but have no endurance limit so suffer more from fatigue so often more overbuilt. Could high carbon steel frames actually be the sweet spot in value, performance, strength and ride quality?

unterhausen

Just for reference, typical high end steels like Columbus Niobium have ultimate tensile strengths of 160,000 to 180,000 psi, so high carbon steel is what I would consider low-end steel. Most production 4130 bikes are heavier and stiffer than a lot of riders really like. A bike frame made out of high carbon steel is 5-10% heavier, and thus stiffer, but it isn't really different in any way that is of consequence to a rider. To me, ranking steels in that category seems a little pointless. To anyone that's not making thousands of frames a year, the difference in price is inconsequential.

Bonzo Banana

So really high carbon steel is only approaching the lower quality chromoly type steels but a big improvement on lower end high tensile steel used in frames that came before it? 50% improvement maybe. I realise we aren't talking high end frames here but still if there has been an improvement in budget steel frames, it's nice to know meaning the budget steel frames aren't as bad as they used to be, a bit lighter a bit more competitive.

Would that be fair to say or are there other factors of importance?

If you were buying a bike one with a conventional high tensile steel frame (low carbon) and another with a high carbon steel frame everything else being equal it makes sense to buy the high carbon steel frame bike? Everything else being equal you would expect the high carbon steel frame bike to be lighter.

If so it makes steel more competitive again with aluminium because the pricing of high carbon steel is still very competitive and below that of aluminium it seems for budget bikes so allows some small improvements elsewhere in a bicycle, drivetrain etc. It would also explain why many low cost Chinese bicycle manufacturers are pushing high carbon steel as something better.

Kontact

I guess I didn't make it clear - all the steels you're likely to run into for bikes are "high carbon steels". It is something of a nonsense term in this application and comes from the marketing department.

The important difference between bike tubing steels is not the amount of carbon content but all the other alloying elements.

McBTC

SS like Reynolds 953, for example, is said to be competitive with titanium not alloy -- i.e., something exotic and providing unique, distinguishing and more desirable riding characteristics and not alloy which despite it's challenges to work with, better suits mass manufacturing techniques (e.g., hydroformed 6061) and accordingly, comparatively inexpensive, which is interpreted to mean...cheap (e.g., not custom) but nevertheless, providing great value for the dollar.

Bonzo Banana

I didn't think that was true because the older weaker cheap high tensile steel frames with low carbon were exceptionally easy to weld and could be welded by anyone with basic equipment but these newer high carbon steel frames are harder to weld and need better equipment. The way I read it is many of the smaller bicycle factories which weld themselves are still welding low carbon (easy welding) high tensile tubes for their frames but new improved processes allow for welding high carbon steel frames with heat treatment to enable a cheap not too brittle frame of decent tensile strength. I didn't think 1010 to 1018 were considered high carbon steels which are the steels used for more basic high tensile bike frames of the past I thought they were low carbon steels. 1045 is classed a medium carbon steel and beyond that perhaps somewhere around 1065 we have high carbon steels. So I wouldn't of thought they were the same. I think there has been some movement in manufacturing towards using high carbon steel in bicycle frames thanks to new welding equipment and processes. Weight of steel frames has been dropping for these cheap steel frames and they are much more competitive in weight now.

taras0000

Bonzo Banana, I think you're missing the one crucial fact that has been pointed out to you already; that high carbon steel is a VERY broad category, and encompasses many different variations in alloys, tensile strengths, and fatigue limits.

It's hard to figure out exactly what/where you are trying to go with this post. It almost comes across as if you think that the older Hi-Ten steels are better and you are looking for definitive information to unseat that opinion, and you're sort of wandering around the information given. If that's the case, there is lots of information available on the web about different steel recipes and what they are used for. You may want to brush up on this information so that you can better tailor the questions you ask for the information you need. I'm not saying this to be crass or rude, but you'll be able to gather more information in a shorter period of time than you will with a question and answer technique on a forum. Some more general knowledge/information will help you in getting the answers you are looking for.

Kontact

Carbon content in steel runs from .1% to 3%. There is no set "medium carbon steel".

Hi-ten is easy to work with because it is thick and isn't heat treated. The steels that are difficult to work with have very thin walls and special heat treatments to make that okay. They need to be welded/brazed with more care because they are thin and can only take so much heating.

Difficulty goes along with thinness. If you had really thin low carbon tubing you'd still need to be careful - its just that you can't make cheap alloys too thin.



I'd get the carbon content thing out of your head. The air hardening steels have a lot of carbon, and are less susceptible to overheating than some lower carbon steels.

McBTC

It is said that modern SS doesn't have enough iron to be magnetic. Alloying elements in the making of age-hardening stainless steels have a lot of chromium. Reynolds 921 SS, for example -- which is not as hard as 953 (921 is more like the hardness of heat-treated chromoly steel) -- is said to have the chemical composition of “21-6-9,” i.e., 20.32% Chromium, 6.68% Nickel, 9.3% Manganese, 2.6% Carbon, 2.1% Phosphorus, 0.3% Sulfur, 6.7% Silicon, 2.9% Nitrogen

Kontact

Most stainless steel is magnetic. The only stuff that isn't is the soft stuff sinks are made of. My stainless refrigerator is covered in magnets.

Andrew R Stewart 

At least one brand/version of SS steel bike tubes is slightly magnetic. If I had tested the tube I found this to be the case with I might still have a full length SS tube. Instead I trusted the source and found out after trying to bronze braze it to a shell. Andy

McBTC

Reynolds "super-steel"

Bonzo Banana

My point certainly isn't that older hi-ten steels are better my point is some of the largest Chinese frame manufacturer's seem to have moved to a high carbon steel and have improved their budget steel frames and are now selling them as 'high carbon steel' and certified steel frames seem to have had a drop in weight. My point is these budget steel frames seem to have improved and are now approaching the quality of the lower end chromoly frames and are more competitive weight wise than they used to be. As this is a section about framebuilding I thought the best place to ask about this although really its more about bike industry trends and improvements.

It's difficult to find an example but here is a rare company selling steel frame mountain bikes in the UK at the budget end of pricing which is selling many similar models with one example being aluminium but the others mainly steel and the weight difference actually seems to favour the steel bikes, i.e. on average they appear lower in weight than the aluminium model. I don't think this would have been true a few years ago, there was normally a weight penalty to steel frames.

MOUNTAIN - Greenwaycycles

The world's largest bicycle manufacturer is now doing some fairly sophisticated low cost hydro-formed steel frames that are weight competitive with aluminium which are clearly designed to match aluminium frames for similar models and applications.

HI-TEN STEEL FRAME archive - Tianjin Fuji-ta Bicycle Co.,Ltd.

Often fashion and industry trends create a perceived quality and desired product in consumers minds that means most would not accept a steel framed mountain bike but there does seem to be some improvement in steel frames and many companies now sell these as high carbon steel frames.

Kontact

What makes you think these steel frames are "light"? I don't see a frame weight anywhere, and the complete bike shipping weight seems quite massive.

unterhausen

I just saw a new aluminum bike that interested me, it has a carbon fork. 26 pounds, although it has low-end components that probably make that a lot heavier than it needs to be. I'm pretty sure I could get a similar steel frame significantly less than that, particularly with a carbon fork.

Production steel bikes are usually fairly heavy. Some companies will occasionally build one with high-end tubing, like 853. But if you are building a frame in a hurry with relatively unskilled workers, it's best to build them heavy.

Rudebob

The use of “high tensile” is totally subjective and has no direct correlation to any specific mechanical properties that can be asserted to any material. It is a marketing term. Steel, even 1005 low carbon, is high tensile by comparison to most other non-metallic materials, and theoretically is valid. I mean a coat hanger is significant higher in tensile than pizza crust, right.

The term “low alloy steel”, however, usually refers to materials that have specific alloying elements (such as chrome, nickel, molybdenum, vanadium, etc.) within a range to provide desired mechanical properties, whether solution annealed, normalized or heat treated. However, even the term “low alloy steels” refers only to a class of material. Without specific alloy identification, one still knows very little regarding the actual mechanical strength (and condition) unless they actually test it.

The term “low carbon” steel usually means that mechanical properties are controlled primarily by carbon and manganese presence (although limits for sulfur, phosphorous and silicon are usually controlled as well).

I suspect the use of high tensile as is comes from some Asian countries is really more of a general term since the actual material types they use may change from different production runs, suppliers and such. They are not asserting any specific alloy, just that it is strong-well at least coat hanger strong.

Years back my company performed a failure instigation for an individual whose face looked like it went through a cheese grader. He had purchased a “mountain bike” from one of the major US “membership” warehouse stores. The frame and forks were labeled “chrome-moly”. However, the forks collapsed on a rough downhill run resulting in massive injuries. A quick chemical analysis of the forks showed the material to be low carbon steel (1018 if I remember correctly). I never heard how much received in the lawsuit, however, about 6 months later the same big box membership store was selling the same bike-this time labeled “high tensile steel”.

One other thing to keep in mind is that steel becomes much more difficult to weld once the carbon content gets to 0.40 percent or higher. At this point pre and/or post heat treatments usually need to be utilized to prevent cracking. This is the difference between 4130 and 4140 chrome-moly steel for example. I say this in that most production frames built with cost considerations in mind will utilize lower carbon steels as means of controlling costs from these additional processes. That means most of your “high tensile” low carbon steels are going to be limited on strength. For this reasoning, it is unlikely that high carbon “Spring temper”steels would be used.

'bob

fietsbob

Machinery's Hand book has 4+ pages of charts of AISI-SAE standard steel alloys .. dense small print..
(about 400 pages in from the front cover.. of a 2500 page book )


https://new.industrialpress.com/machineryhandbook







.....

Kontact

Actual "high carbon" steel isn't used because bicycle tubing doesn't need to be as hard as high carbon steel can make it. If you made steel tubing with higher carbon content it would be relatively brittle at medium hardnesses.


"Low alloy" has less alloying content, but is considered a different animal than simple carbon steels, like the 10xx series which also use carbon and manganese. 4130 is a low alloy. Tool steels have even more alloy content.