Wilsons Sandbox

Most Stainless Steels will "work harden" - WORK being Force times Distance. Stainless doesn't stress harden, but it does strain harden. Strain being a distance. So long as the applied stress (call it force for now) doesn't cause a strain then no it won't harden. Lets talk dislocation theory for a spell and you'll all be asleep, I'll skip that for this post. ;} There are basically three types of stainless steels, Austenitic, Martensitic and Ferritic. We'll deal with the first two as they are the most common and the ones that are used for most applications. The Austenitic stainless steels are not heat treatable, that is they don't get hard with a heat treatment. They do get hard with WORK. Martensitic stainless steels typically only get hard with a heat treatment, and only work harden a little bit. A full hard Austenitic can be as strong as a modestly treated Martensitic BUT it is not as tough. Tough -relating to the amount of work needed for failure, more specifically it is the material's resistance to crack growth. (we don't need a fracture mechanics lesson here) We need strength and toughness on our 650cc Vibrators. Austenitic won't give you both. AND Austenitic is the common grade for your bolts at the marine store and the hardware store (18/8 or 300 series). Most of the 400 series are Martensitic, that is you can heat treat them and in some cases enjoy good toughness. BUT you couldn't afford a set of bolts made of 400 series stainless. The alloys are expensive, the processing is expensive and you'd be better off using a coated alloy steel bolt in its place and deal with the corrosion. Now you're gonna run to your Metals Handbook and give me a whole bunch of "Yeah but" or "What about" and you'll find plenty to be outside the norm of general concepts. Welcome to metallurgy. The alloys nowadays are amazing, and there are simply too many to list here as examples. Let me add that all the bolt alloys have to have at least 10% elongation. Then the grades are specified with minimum tensile strengths.... Grade 8 - 150 ksi Grade 7 - 133 ksi Grade 6 - 133 ksi - 140 ksi (yes that's right... this is stress and not load - so diameters are important to consider and are specified with size limits.) Grade 5 - 105 ksi - 120 ksi Grade 3 - 55-100 ksi Grade 2 - 64-69 ksi Grade 1 - 55 ksi Well Grade 8 is only possible with one of the Austenitic stainless (at least what I have listed here in front of me today) and that is 301-1/2 hard. But in the Martensitic SS's you can do it with a 416, 414, 430, 431 and I'm sure there's a bunch more that I don't have listed. So why not make Grade 8 stainless bolts out of 301 1/2 hard. Well.... for a couple of reasons... and this isn't to say that it can't or isn't done.... It's just not common. First, the processing to achieve a 1/2 hard 301 includes an extensive drawing process, but then the threads are rolled and the head is forged. You have a mixed hard bolt by the time you get done. If the dislocation structure across the harness profile isn't matched well (that's really relative) then you end up with a bolt that has good tensile strength but really poor thread shear strength. Not good. So then you stress relieve them and then you are heading right back towards the annealed state and those properties just aren't good enough. There's too many scenarios and a million different ways to solve metallurgical problems (hence the enormous numbers of engineered alloys), so I'm not saying that it can't be done, or isn't done... It's just not worth it. Well I'm about out of stuff to add at this point. If you have any questions, feel free. Keep your "Yeah buts" and "What abouts" to yourself, as my only reply will be "that's metallurgy" It's as much an art as it is a science. To answer specifically... It can.... both (most cases).... 10.9 doesn't mean anything except to the manufacture, it doesn't fit a standard method.....It is better than stainless, but you can get stainless that is as good and in a few instances better than "Regular Steel" (what ever regular means). Longevity of your frame bolts requires a few things. First that they are free from imperfections and corrosion, second they are properly torqued, and third.... they'll only break when you absolutely can't afford (having many meanings) to have one break. Oh and DU is barely strong enough for Grade 1 bolts... But yeah it is highly pyrophoric. LaterZ Dash At 10:33 AM 2/5/2001 -0800, Rich Kickbush wrote:

>Calling all metallurgists - Stainless hardens with abuse? Does that >mean it becomes stronger, or more brittle, or both? >I have hardened steel bolts in my sub-frame that have 10.9 written on >their head - what grade is this? I assumed that these would be better >than stainless, since you can't get stainless as hard as reg. steel. Is >this true? >PS I second the call to check and maybe upgrade the frame bolts. I >sheared mine, and it sucks...'specially in the middle of Guatemala... > >Rich > >Swede wrote: > > > --- In DSN_klr650@y..., garagedoor79@h... wrote: > > > > > > On the same topic, how are the grades of bolts measured? Is the > > > lower the number stronger, or the higher the number stronger? > > > > > > Karl > > > > Grade 5 is pretty much standard, grade 8 is hardened, then you can > > get into stainless which will harden with abuse (work hardening). > > Then there's depleated uranium...wait that's artillery, sorry! One > > hit with a hammer and B-BOOOOMM!

Disregard my previous brain poo. 10.9 is the metric equivalent of our US grade 8. Sorry about that. LaterZ Dash

>At 10:33 AM 2/5/2001 -0800, Rich Kickbush wrote: > >Calling all metallurgists - Stainless hardens with abuse? Does that > >mean it becomes stronger, or more brittle, or both? > >I have hardened steel bolts in my sub-frame that have 10.9 written on > >their head - what grade is this? I assumed that these would be better > >than stainless, since you can't get stainless as hard as reg. steel. Is > >this true? > >PS I second the call to check and maybe upgrade the frame bolts. I > >sheared mine, and it sucks...'specially in the middle of Guatemala... > > > >Rich

I am no metallurgist, but it is my understanding that stainless steel bolts do not have near the shear strength that carbon steel grade 8 bolts have. I use stainless fasteners in some of my projects because of salt water, but usually go up a size or two to compensate. Here are specs from a fastener catalog: Grade 2: Min. tensile strength 60,000 psi Grade 5: Min. tensile strength 120,000 psi Grade 8: Min. tensile strength 150,000 psi Grade 9: Min. tensile strength 170,000 psi Also has design modifications to make it stronger. (Thicker head) Anything less than grade 8 is only recommended in applications where strength is not an issue. Since the most common stainless steel, 18-8 Stainless has a minimum tensile strength of 75,000 psi, it doesn't qualify for anything stressful. I never heard the one about stainless hardening with use before. That is a good one. 8^) Use extreme caution when substituting bolts and nuts on your bike! (Or anywhere else!) -- bierdo ********************* Rich Kickbush wrote:

> Calling all metallurgists - Stainless hardens with abuse? Does that > mean it becomes stronger, or more brittle, or both? > I have hardened steel bolts in my sub-frame that have 10.9 written on > their head - what grade is this? I assumed that these would be better > than stainless, since you can't get stainless as hard as reg. steel. Is > this true? > PS I second the call to check and maybe upgrade the frame bolts. I > sheared mine, and it sucks...'specially in the middle of Guatemala... > > Rich > > Swede wrote: > > > --- In DSN_klr650@y..., garagedoor79@h... wrote: > > > > > > On the same topic, how are the grades of bolts measured? Is the > > > lower the number stronger, or the higher the number stronger? > > > > > > Karl > > > > Grade 5 is pretty much standard, grade 8 is hardened, then you can > > get into stainless which will harden with abuse (work hardening). > > Then there's depleated uranium...wait that's artillery, sorry! One > > hit with a hammer and B-BOOOOMM! >

Go here for everything you ever wanted to know about nuts and bolts etc. http://www.americanfastener.com/techcharts.htm Russel'r -----Original Message----- From: Dan Oaks [SMTP:bierdo@...] Sent: Monday, February 05, 2001 3:43 PM To: Rich Kickbush Cc: Swede; DSN_klr650@yahoogroups.com Subject: Re: [DSN_klr650] Re: Upper rear frame bolts I am no metallurgist, but it is my understanding that stainless steel bolts do not have near the shear strength that carbon steel grade 8 bolts have. I use stainless fasteners in some of my projects because of salt water, but usually go up a size or two to compensate. Here are specs from a fastener catalog: Grade 2: Min. tensile strength 60,000 psi Grade 5: Min. tensile strength 120,000 psi Grade 8: Min. tensile strength 150,000 psi Grade 9: Min. tensile strength 170,000 psi Also has design modifications to make it stronger. (Thicker head) Anything less than grade 8 is only recommended in applications where strength is not an issue. Since the most common stainless steel, 18-8 Stainless has a minimum tensile strength of 75,000 psi, it doesn't qualify for anything stressful. I never heard the one about stainless hardening with use before. That is a good one. 8^) Use extreme caution when substituting bolts and nuts on your bike! (Or anywhere else!)