Hi everyone,
I've posted in this forum about Coscast blocks and the fact that they also have porosity issues according to V8 Developments.
The question I have is that logic tells me that even if you replace the liners with "top hats", eventually, the cooling system pressure is going to force the coolant between the liner and porous block downward to the oil pan. Maybe even up to the head area passed the flange.
It seems to me that top hats only prevent the Rover flaw of dropped cylinders. Not porous block.
It's a patch not a fix.
Does anyone have any experience with this?
Are the newer 4.6 blocks any better?
Or, should I just be looking into a Ford or Chev aluminum v8??
Any thoughts?
Trip
The LS motors do look very good, especially with DI and VVT.
Hi Jim,
Pardon me for not knowing. Whats DI and VVT?
I'm guessing that DI is direct injection, right?
Trip
Yes, and variable valve timing. Both together is a serious improvement in the IC engine.
The LS is a great engine. You can pull one out of a basic Camaro with 320 hp right from the getgo. Don't get me wrong, I love the Buick/Rover but it's a hobby of customization. You got to love it. You know what I mean?
Jim, since learning that the supposedly "improved" Coscast blocks are now coming back with the sme porosity issue, I've been doing some research on the Chev and Ford options. I think that I could go in a whole other direction!
Jim, I'm liking what you're saying. DI and VVT are really fascinating new options. I wonder if it can be done at a reasonable price?
Trip
Nicolas, yes I agree with you. The LS is definitely a sweet motor. Do you know if that the same variant that's used in the C6 Corvette?
I also agree that getting 320HP right from the start is a good thing. I do know what you mean!!
Trip
If you wanted to use the DI the best approach would be to get a complete donor car and expect it to be involved. For instance, the Megasquirt gurus suggest switching back to plain sequential (duh!) So to make it work you'd need every sensor and input on the car to keep the controller happy. Not insurmountable, but not the easiest thing either. Lots of wiring. The new Camaro (2010) uses DI and VVT and they are already showing up in wrecking yards. Not sure how long the Corvette has been using it or what other cars are, maybe the Caddy.
Jim
Jim, I'm amazed that 2010 Camaros are already at wreckers! I guess it's too much car for some people to handle.
I see what you're saying regarding getting a whole car for the controllers etc. that makes tones of sense. Maybe I'm getting carried away with my project dreams. Perhaps I should start considering a more basic start and then as the DI VVT bits become more readily available and also on the aftermarket, then I can evolve the motor to that level.
Can you imagine if something fails in the electronics or computer? Roll in the wheelbarrow full of money.
I'm thinking, if I start with a solid base motor as a platform, there will be lots of room to grow, later(?).
Now that I've decided to go SB Chev or Ford over a Rover V8 (I still looove the motor, tho), it seems that the possiblities with a Ford or Chev are endless and at far more sane prices than the Rover option. Horsepower seems to be easier/cheaper to make with Chev and Ford.
I know you have a 215 in your car. You've certainly done very well with it. I think it's about your advanced skill level and ability to get around the 215 issues... And, knowing where to get the bits needed a reasonable prices.
I do wonder what it would cost for a whole doner car, though? Hmmm.
Trip
Check craigslist. I've heard of donor prices below $1500, depending. (not 2010 Camaro) Typically I don't think DI and VVT is retrofittable to earlier versions of the engines in a lot of cases without a head change at the very least, so do your research well before you start. Headers and engine mounts for SBF/SBC will not be available for the TR7/8, and using ones made for something else will be a crapshoot. Just a couple of issues to consider. Dan B is looking at this also, and based on the Buick V6 in Edith's TR7 we've about decided that's the most sensible approach. Equal power to the Rover (or better depending on options) and an easy install with a complete and well developed swap kit available and no crossmember change. It sits well back in the engine compartment also. Doesn't sound like a V8, be we're going to add another pair of resonators and a crossover to the system and I think it'll sound good.
Jim
I hadn't even considered the Buick V6 until you just mentioned it. Looks like I have even more research to do.
I'm pretty certain that even with a lot of HP added and a funky exhaust, the V6 won't have that torquey pull of an 8. Especially off the line.
Good point you make about the headers and engine mount issue. Not sure how to address that one. I've always wanted to learn to weld and fabricate, tho. Maybe this is a good reason to do it now. I noticed a few articles here regarding how to weld that I skimmed. I'm going to read those too.
I agree, DI and VVT are a whole new ball game.
BTW... Is Dan B's V6 TR7 like one of those gifts that guys buy for their wives but is really for him? "Honey, I got you a brand new power drill and sander for christmas" Wink, Wink.
Trip
Oops, a little miscommunication there Trip, Edith is my wife, I just gave her the TR for her birthday. It's definitely hers, I'll stick with the MGB, just wish I was a little closer to having it back on the road. Dan bought his about a year ago as a "beater" (it's anything but) so he could keep his TR4 in the garage and we've been talking engine swap ever since. At some point the engine will go.
I think the torque of the Buick V6 will surprise you. Remember the Buick Grand National? That's the engine. But everyone has to decide for themself. The swap kit is made by John's Cars in Texas. There is even a version of the engine that came from the factory with an Eaton blower. Very nice powerplant. Plenty of online support and a wealth of performance parts. Edith's car has the mid 80's 2 barrel 231cu.in. version. It does quite well but it isn't a performance engine. The later 3800's were much better. The reason this swap makes sense is because there is a kit. But I understand it is only available as a complete kit (with some options) and he doesn't sell just the headers and engine mounts. Still, I think the price is probably reasonable. That and the Rover swap are probably the two most common and the most sensible. Next would be the Buick 300, which should be the same as the Rover swap but 80 lbs more weight from the iron block and an extra 85 cubic inches. I'd take that trade off. Then possibly the 340 with 300 heads (the '64 aluminum ones) or the new TA heads (much better) but the intake is an issue as there is not a mass produced 4bbl alloy one available. (and IR intakes are expensive) Then SBC or SBF as headers and mounts will have to be built.
As for the welding, you can learn to do that easily with a mig welder and it would work for the mounts, but mig isn't the best for welding thinwall tubing. Gas welding works very well but does take a good bit of practice to get the hang of it. Tig obviously works the best but there you have the practice plus the cost of the equipment so there's a significant entry barrier. For what that costs you can buy the mig, the torches, and an AC stick welder and still have money left over. Those three will handle all but the most demanding welding tasks. But, you could just as easily buy the parts for the Rover (or Buick 300) swap or the kit for the V6 swap and just bolt it together. Tough choice. The good news is that you have plenty of choices.
Jim
Pardon the confusion about Edith.... Happy birthday, Edith!!!
Must be nice having two cool cars in the garage!
I definitely do remember the Regal GN and the GNX too. Ahhh, had posters, all the feature R&T copies, photos from car shows.
The GNX was turbo charged. Any chance that you'll go that route with the TR7? Sure would add that pull!
Thanks for the welding types insight. I'm seeing that there's so much more to it than I ever imagined... Arrgh! I think it's going to take longer to get there than I thought. Do you think there's good quality used equipment out there, or is it all zapped by the time it gets sold?
Trip
It's a mixed bag. You're just as likely to get lucky as to get screwed and vice-versa. the best way to buy used welding equipment is: 1) you know the seller, and 2) you buy from a welding equipment supplier. For cheap equipment go with 1 or take a chance, for more high end go with 2. That way you know it will work, or they will fix it on their nickel. Or buy new. Some of the new equipment is surprisingly affordable but you have to strike a balance between cost and capability. Less expensive usually means lower amperage capacity. You can find deals. For instance, I bought a used square-wave tig from a local supplier and was all set up for under 2 grand. I could have bought a new inverter type unit for about the same money and it is much more portable, but it has neither the capabilities or the power. I doubt you'd be ready to sink that much into it though, before learning how to tig weld.
Edith's car will not get the turbo. I can't see that as being a good idea no matter which way I look at it. Anyway she doesn't care that much about the power, just wants to drive it and look good. That's fine by me, we're polishing the apple and probably will be for the next couple of years. In the meantime it can probably outrun better than half the cars out there so she'll be fine. (Did I mention she owned a new Trans Am when she was 19?) I even avoided the 4bbl swap by modifying the air cleaner base. (The John's Cars kit is based on the 4bbl engine. With the 2bbl the air cleaner is too close to the hood latch and interferes with the fresh air plenum- which you want to keep.)
One other thing. Having the two cars is nice, but it's a good idea to keep in mind that you do not own your possessions, they own you, and they require you to provide for their needs.
Jim
2 grand for a welder and, it's used? Oh my gosh! What am I getting myself into?
You're right though, Jim, I'm a long way from your skill level and requirements. If I can just learn the basics that I need to do a reasonable level of tasks ie: the mounts and some metal bodywork (rust repair), then I'll advance the skills and equipment as needed.
I'm taking your advice [ 2) you buy from a welding equipment supplier. ] and will look for a good one at reasonable price.
Brand new Trans Am at 19, you say. Wow, that's verry awesome!! She sounds like a cool lady!
RE: the 4BBL There's a great deal of satisfaction when you can find a solution without having to go the mod kit route, carb or otherwise.
"it's a good idea to keep in mind that you do not own your possessions, they own you, and they require you to provide for their needs."
Yes, good point. I'm starting to see how true that statement is.
Thanks kindly for all the advice, Jim.
Trip
I bought a nice 240v gas shielded MIG welder to start out as a beginner and it worked out really great. I taught myself to weld some pretty thin sheetmetal with it. Some of it in the 20 ga. thickness. SUPER frustrating. The entry cost is good and you definitely get the feel for welding. It's pretty forgiving if not a bit fast. Really versatile and easy to use. The best part is you've just got a trigger and a steady hand to worry about. You can weld a bead laying on your back pretty easily.
For my MIG setup I spent just under $900 and for that I got a nice Hobart 180 Welder (up to 1/4" Steel maxed out), Shield, Jacket, Gloves, 3 ft. tall tank (exchange), Big spool of wire, 30 tips, Tip conditioner, Pack of cleaner pads,... I might be missing something but you get the gist.
I was always a fan of old school gas because you get so much control but it takes forever to lay a bead. I'm just now graduating to a TIG. You are not kidding about the cost. WOW!! I managed to happen upon a nice entry level Miller for $1100. Great deal but a bit limiting in the thicknesses of metal and cycle. Being able to weld aluminum then just switch current and weld steel is pretty cool though.
My wife just asked me when I was going to turbocharge her car. LOL! My other car is an SRT 4 turbo. She loves driving it. She gets back in her car and has nothing at the top side. She hates that. She's hot.
Hello Nicolas,
My head is spinning!! ...eeeeee
I'm confused. MIG first, then TIG?
Do they both produce the same end result but that TIG can weld thinner and thicker metal?
I hear aluminum and chromoly take super advanced experience/talent.
Also concerns about aluminum toxicity Yikes!
Isn' there also a huge issue with UV radiation?
The self darkening shields are popular but, and here's the big but, my logic tells me that the flash before the shield darkens will definitely cause eye damage especially over time. Does that sound right to you?
Maybe someday would like to advance to be good enough to build a roll cage(?)
Man, you and Jim have really cool wives!!!!
Trip
TIG welders give professional fabricators more control so that they can finesse difficult welds.
Some very nice smaller MIG welders can be found used for $500 or less. I think it's worth shopping around for smaller "professional grade" machines, as opposed to those sold at the big box stores, but you don't need to get too carried away. You'll find a small MIG welder is extremely handy around the shop. Often, you can make serviceable welds in thicker material if you're patient enough to chamfer back the base material and then build up the weld over several passes.
On the occasions when I need aluminum welded, I do all the prep work and then take the work downtown to let a real pro do it.
IMHO, chrome moly is way over rated. If you use the wrong wire or fail to properly heat treat the finished welds, they'll be more brittle than welds in good old mild steel. Heat treating is a specialized skill, not something for home shops. How much weight are you going to save to justify using an expensive material that needs to be professionally heat treated?
When you buy an auto-darkening helmet, don't settle for one of the cheap Chinese helmets. The brand you want is Jackson. Last time I checked, there was a big difference in how quickly they sense a spark and darken. Without an auto-darkening helmet, I wouldn't get much welding done.
Info on welding chromemoly:
TIG WELD 4130!
The Lincoln Electric Company, Welding Services. June 2000
Yes, you can TIG weld 4130 tubing up to .120" wall thickness easily with the techniques and procedures described in this bulletin. Answered are the top ten most frequently asked questions about TIG welding 4130 Chrome-Moly. These attached procedures apply to typical sporting applications such as experimental airplanes, racing car frames, roll cages, go-carts, bicycles, and motorcycle frames. The suitability of these techniques and procedures must be evaluated for your specific application.
Q. Can I weld 4130 using the TIG process?
A. Yes, 4130 Chrome-Moly has been TIG welded in the aerospace and aircraft industries for years. As with all welding, proper procedures and techniques must be followed.
Q. Do I need to pre-heat?
A. Thin wall tubing (< 0.120" wall) applications do not typically require the normal 300ºF to 400ºF pre-heat to obtain acceptable results. However, tubing should be at room temperature (70ºF) or above before welding.
Q. What filler material do I use?
A. Although there are several good filler materials, ER80S-D2, is one you should consider. This filler material is capable of producing welds that approximate the strength of 4130. ER-70S-2 is an acceptable alternative to ER80S-D2, as is ER70S-6, although the weld strength will be slightly lower.
Q. When I use ER70S-2 filler material, do I give up strength for elongation?
A. Yes. The filler material, when diluted with the parent material, will typically undermatch the 4130. However, with the proper joint design (such as cluster or gusset, for example), the cross-sectional area and linear inches of weld can compensate for the reduced weld deposit strength.
Q. Why is 4130 filler metal not recommended?
A. 4130 filler typically is used for applications where the weld will be heat treated. Due to its higher hardness and reduced elongation, it is not recommended for sporting applications such as experimental airplanes, race car frames, roll cages, etc.
Q. Can I weld 4130 using any other filler metals?
A. Some fabricators prefer to use austenitic stainless steel fillers to weld 4130 tubing. This is acceptable provided 310 or 312 stainless steel fillers are used. Other stainless steel fillers can cause cracking. Stainless filler material is typically more expensive.
=================================================================================
Q. Do I need to heat treat (stress relieve) 4130 after welding?
A. Thin wall tubing normally does not require stress relief. For parts thicker than .120", stress-relieving is recommended and 1,100ºF is the optimum temperature for tubing applications. An Oxy/Acetylene torch with neutral flame can be used. It should be oscillated to avoid hot spots. ( 1100* is defined as: "Red heat, visible in the sunlight" [Machinery's Handbook] which is just at the point where you can start to see a glow. Dark red or cherry red is too hot. Jim)
=================================================================================
Q. Do I have to pre-clean 4130 material?
A. Remove surface scale and oils with mild abrasives and acetone. Wipe to remove all oils and lubricants. All burrs should be removed with a hand scraper or de-burring tool. Better welding results with clean materials.
Q. Do I need to back-purge 4130 material?
A. Backpurging is not normally necessary, although some fabricators do. It will not hurt the weld and may improve the root pass of some welds.
.
Q. Should I quench the metal after I finish welding?
A. ABSOLUTELY NOT! Rapid quenching of the metal will create problems such as cracking and lamellar tearing. Always allow the weld to slow cool.
More Information on TIG Welding Chrome-Moly 4130
Find out more about Lincoln Electric's professional line of TIG welders here
Or, check out Lincoln cut length TIG welding filler metals here
WELDING SPECIFICATION: Aircraft and Motorsports
GENERAL INFORMATION
* Remove all oxides and burrs within 3" of weld area.
* Acetone wipe to remove all cutting oils.
* Assemble and tack weld in joint in a minimum of four (4) places with TIG.
* Tubing should be at minimum temperature of 70ºF (room temperature.
* TIG weld per parameters specified using Lincoln's Precision TIG™: The Power To Perform. 185, 275 or 375.
I continue to be amazed at the knowledge, experience and generously shared insights and lessons here.
I'm learning more just from this forum than all past sources before - combined! Thank you all very much for taking the time to help me understand.
Curtis, I had believed that chromoly is not only lighter, yes - but also believed that it resisted flex and bending (impact) better than DOM.
Yes, I will definitely avoid the cheap off-shore stuff and as always, search for quality domestic made products.... Sadly, it'll have to be used equipment, tho.
Jim, thank you for the Lincoln Electric answers.
Now I'm all fired up about welding. It's not a mystery anymore!! woo hoo!
I can also understand why people who are top-tier pro welders make a mint.
Trip
There are a couple books I'd very strongly recommend to anyone with an interest in these subjects... actually, I'd recommend the whole set of Carroll Smith's books: "Prepare to Win", "Tune to Win", etc. They're all very readable and extremely informative, and at times I think Smith is quite funny in a sarcastic, tongue-in-cheek way.
In "Engineer to Win", Smith provides a whole course in metallurgy.
On page 79 he has a sub-heading called "Do It Yourself Heat Treating" and the whole message of that section can be paraphrased simply: "don't try this at home". I don't know... I haven't broken enough parts to have developed a lot of empirical knowledge, but my guru has told me not to use 4130 unless I heat treat it (page 63), and then he told me not to kid myself that I could heat treat it without potentially leaving stresses in the part. He goes into some detailed and specific warnings too, like this one: "Make sure there are no sharp edges or corners - inside or outside - ANYWHERE on the parts to be heat treated (they are guaranteed to come back glass hard and are virtually guaranteed to come back complete with 'quench cracks,' which WILL grow.)" and this one "With long straight pieces, make sure that they are HUNG in the oven, not just laid on the racks."
But... doesn't that advice simply fly in the face of, "don't try this at home..."?
I definitely won't be "trying this at home". I think though, that kind of the knowledge will come in handy when talking to a pro shop at their level and making sure they actually go about doing that sort of work right ie: hanging long straight pieces etc.
This whole heat treatment business is a black art to most people, but the basics are pretty simple and it only starts to get complicated when you get very particular about straightness, surface finish, fine details and things like two stage hardening processes. For most general purposes it just isn't that complex. For instance, 4130 is not a particularly complex alloy and does not have a particularly high level of alloying elements added. A little chrome, a much smaller amount of molybdenum, a dash of carbon and near trace amounts of a few others. In most cases it is used in the annealed condition (soft). That's what you are doing after welding it, annealing or softening the metal in and adjacent to the welds. To anneal carbon steel and most alloys you simply raise the temperature of the metal enough to make the metal soft and cool it slowly enough that the grains do not freeze which is what creates the hardened state in the first place. As you heat it, more and more of the grains convert, (or "unfreeze") which is why tempering is effective in reducing brittleness. So, at anything over about 500 degrees or sometimes less you begin to reduce brittleness, beginning at any thin sections, corners and such and proceeding into thicker sections. This is why a heat soak in the oven is needed for complete through hardening or annealing of solid pieces. The heating creates a phase change in the grains or structure of the steel and rapid quenching freezes the grains in the changed state. Not all grains are converted (because quenching is not instantaneous) and subsequent heating allows more and more grains to revert. The reason sharp edges create stress risers is because the temperature goes up there the earliest and the most and likewise quenching is the most violent there. But likewise tempering has the greatest effect there, as does annealing. (the difference between tempering and annealing is one of degree only-- in both time and temperature)
So it's not exactly rocket science. Things like inert gas heat treat ovens just allow finer control of the process and prevent surface oxidation (as does wrapping in stainless foil) and if you think for a moment about that long bar on the floor of the oven you can see why it warps. It simply will not heat evenly. Nothing magical about it at all. Most parts either are too small to show warpage, are not critical, or will be ground afterwards. As for welding a cage, as long as the weld areas are annealed it will be fine. And the reason for trying not to get it too hot is not because it will weaken the steel, since it can't get any weaker than in it's fully annealed state anyway, but to keep from burning it which is basically surface oxidation. It is possible however to introduce impurities into the metal such as carbon and seriously screw up the surface texture both of which can weaken it, if it is heated to a near molten condition or held at an elevated temperature for an extended period. So a just barely visible glow is good enough.
Now let's say you had access to a very large heat treat oven. In that case you could take your 4130 or 4140 chromemoly steel, weld up a cage, heat it, quench it, temper it (sometimes called "drawing it blue") and end up with a fully heat treated structure which would be much stronger than a standard cage. It would outperform the annealed cage in ever respect except one. It would be somewhat more susceptible to tearing of the steel due to the additional hardness. But it's yield strength would be so much higher that it pretty much eclipses that concern. The downside of course is cost. Also bear in mind that practically any carbon bearing steel can be made brittle, soft, or anything in between. It all depends on how you harden and temper it. So this is all just a tool to be used by those who have learned how, and the gas torch is the most basic tool in the arsenal.
Jim
Suspension links are the most tempting place to use chrome moly.
But roll cages? I know of one MGB GT V8 race car with a chrome moly cage, but frankly I don't get it. If safety (or chassis rigidity) is your first concern and you want to make a cage stronger and stiffer, IMHO the best way to do so is to accept the weight penalty and use 1.75" diameter tubing instead of 1.5" diameter tubing. The individual tubes would be stiffer, but more importantly you'd benefit greatly from having more weld area at every single joint. Cages are normally built in situ. Even with a TR7 convertible, for example, it's going to be very tricky to build a cage outside of the car and then install it. Normally, one tube or hoop is installed before the next tube or hoop is even trimmed to length. Yes, you could possibly use your acetylene torch with a rosebud tip to carefully heat treat every joint of the entire cage, but it would be a real pain in the butt to do so. Getting to the back side of all those joints to evenly heat them all the way through, when they're blocked by the unibody sheetmetal? Mild steel is so much easier to deal with!
It's a good point Curtis, and really, the extra expense and effort only makes sense in an all out racing effort where every ounce of weight reduction counts, or where space is a factor. Then, if you can get at it to tig weld it, you can also follow behind with the rosebud to anneal it. Not much difference at all in terms of space needed and heat generated. Or if space is that tight, the cutting tip will do fine also, just don't hit the lever. It only has to be warmed well. At 400-500 degrees bare steel begins to color. Between that and 1100 it will go through the blue spectrum ending up a very light blue at around 650 degrees. By this point only the deep stresses remain, as the surface stresses have mostly been relieved. From that point until it begins to give off light as a very dim dull red glow, the rest of the stresses are relieved and the metal is fully annealed. It's important to recognize that this is a progressive process. It doesn't just fall of the proverbial cliff at 1100 degrees to the fully annealed state. Plus as already noted any projections or edges will get hot first and therefore get soft first. Inside corners will need the most attention. There is virtually no need to heat soak the metal as the tubing is thin enough that the inside will be at roughly the same temperature as the outside.
But let's take the case of the forward struts on the Jag IRS for the MGB-Roadmaster for an example. Those are made from heavy wall mild steel tube and are probably the weak point in the suspension. To make them a larger diameter would mean making a sharper bend for clearance to the inside of the bend which would make them weaker so it's a compromise set in a dilemma. Perfect application for chrome-moly wouldn't you say? Use the same dimension tube and roughly double the strength without changing the geometry. The entire link could then be heat treated without too much trouble at all.
Jim
In regards to things built in-situ like a roll cage, if you can't heat treat the entire cage - unless you put the whole car chassis in an oven (don't think that's feasible?) - Don't you have to hand "heat soak" the entire tubing length not just the weld points. Are the tubes "pre-heated" and doesn't the high welding heat radiate out along the tube causing other issues?
Trip
You're missing the point Trip. As supplied, the tube is annealed, which means that it is as soft as it ever gets. In order to be hardened it has to be heated, in the case of 4130 probably in excess of 1500 degrees F which would be a bright red and then it is quenched. The only area that ever gets that hot is in the weld zone so that is the only area that is in any danger of being hardened. Therefore that is the only area that has any need of being annealed back to the soft condition.
Annealed 4130 is considerably stronger than mild steel tubing, but is still reasonably ductile. It therefore allows a lighter construction. Only an extreme racing application could ever justify the use of a fully hardened 4130 cage, and that would be a full custom tube chassis. A stock body would never be used due to it's weight.
Jim
Okay, now I understand. Heated to 1500=Hard=brittle. Thanks for the clarification, Jim. I definitely don't have any delusions of turning my home-built project into a full race car but it's fantastic to have the understanding and knowledge, though. I can see how a custom body ie. in pro-drag car could be used with a fully hardened cage.
Thanks again
Trip
Close Trip. Heated and then Quenched to harden. If just allowed to cool it will not get hard. Welds get hard because they are quenched by the cold steel immediately surrounding them. If preheated before welding they will not quench and will not need to be annealed. If quenched intentionally the steel will then need to be "tempered" or "drawn" in order to reduce brittleness in most cases.
Mild steel or the most common low carbon alloy used for tubing, 1018 steel, has about 60-65,000 psi of tensile strength. It cannot be hardened significantly without the introduction of extra carbon, such as is done in case hardening, by heating the metal and introducing a carbon bearing material to it while it is in a state that will allow it to absorb the carbon. But this is a very valuable and useful property that is used quite commonly to create a hard shell or cutting edge. This steel has a .18% carbon content and no other significant alloying materials, hence the 1018 designation.
By contrast 4130 chromemoly has .30% carbon and as annealed has 115,000 psi of tensile strength, nearly double that of 1018 steel. If hardened and drawn to 400 degrees it has 236,000 psi of tensile strength, nearly four times that of 1018. In that condition as pointed out above it will tear upon deformation at a less extreme angle than the annealed metal or 1018 also, but it is also quite clear that it will take four times the force to bend it in the first place. Also since it is a medium carbon alloy it is not particularly brittle. Cracks and work hardening are only a concern if stress risers are allowed in the construction, provided it is evenly hardened and tempered.
As such it's easy to see why it is such a widely used alloy in the auto industry, being very common in things like spindles, shafts, suspension links and much more. Any time you see a suspension part and wonder at the small cross section considering the loads it carries, it's a pretty good bet it is heat treated chromemoly, usually either 4130 or 4140. And it may interest you to know, that as a medium carbon alloy steel, in the fully hardened state it can still be machined.
Jim
Where are these numbers coming from? They simply don't match "Engineer to Win", which is still sitting on the edge of my desk. (I've been working on an article about a Formula 5000 racecar this week, and Smith's books are especially full of insight into those designs.)
(from the chart on page 66 of Engineer to Win)
cold-rolled 1018 sheet and tube: ultimate tensile strength = 82,000psi
cold worked and annealed 4130 sheet and tube: ultimate tensile strength = 95,000psi
(from pg 63)
QuoteThe other side of the 4130 coin, often unknown to (or at least unappreciated by) the racer is that it possesses poor deep-heat-treating characteristics and has an inborn dislike of varying cross-sections. These characteristics make 4130 a poor choice for machined or forged parts. It doesn't machine very well at least in the normalized condition - too gummy. Those people who make hubs, steering knuckles and the like from 4130 are kidding themselves - and their customers. It doesn't make very good shafts either, as in drive shaft, or axle, or torsion bar.
4140 is better for deep hardening and machining, but harder to weld... To get to 236,000psi, we're talking about "4340 modified" (i.e. alloys with vanadium) and big budgets.
Curtis, those numbers are from Machinery's Handbook, 20th edition, 1978. (Current edition is 28th and 100 years in print) I think you'd have to agree that they've had ample time to error check their information, and based on practical experience I would have to agree that the roughly double and quadruple numbers are at least in the ball park. I don't know if Carroll Smith has done any actual tensile strength testing to base his numbers on, or if he is using manufacturer's numbers or what, but 82K sounds awfully high for 1018 and only a roughly 15% increase in strength between 1018 and 4130 just doesn't sound realistic.
But, plate, bar, structural and tube often have different characteristics and different sources can vary widely on their testing results so there's no point in arguing the specifics. The point is that an alloy steel (pick your favorite, there are so very many of them) is going to be noticeably stronger than a low carbon steel and a heat treated alloy is going to be noticeably stronger than it's annealed brother. If you want ultimate strength, a hardened electric arc remelt cobalt alloy is hard to beat, but you can always find a way to spend yet more money. If that 235K number seemed high, recall that it was at a 400 degree draw. Hotter draws yield lower tensile numbers and this has a great deal to do with the variations we are talking about. Commercial 4130 HT or 4140 HT are going to be drawn to a higher temperature than that, but if you'll recall, we were discussing a custom heat treat for an entire cage so we can specify the draw we want to use.
For truly accurate results there is no substitute for a reliable supplier and in-house testing. Since most of us don't have that luxury we have to make do with what is commercially available and the results often vary widely. Thankfully once we are accustomed to a given product we can usually spot a different material very quickly, but within the range of noticeable differences there are going to be some pretty significant variations in all commercial supplies, and that's what good quality control is all about. If you don't like the characteristics of what you are getting it's pretty easy to change the specification. If you don't like the way 4130 or 4140 machines, there are free machining varieties available. If you aren't happy with it as a shaft material, pick one you like better. It's not like there was only one choice or something. But just because one guy doesn't like a particular alloy that doesn't make it a bad alloy either. Could just be the way he's using it, or the particular variety of it he's been using, or the draw temperature of the stock he's gotten, or a hundred other things. Just because a change in the material worked for him doesn't mean everyone else who is using it is wrong either, maybe they are all using a leaded alloy for increased machinability. Or maybe they are using stock supplied in heat treated form, which machines very well with carbide tooling and leaves a nice finish.
What really matters is the end result, and the time and money it took to get there. Alloy steels wouldn't be around unless they served that need very well indeed. But they aren't the solution for everything and sometimes black iron pipe is just the ticket. I just wouldn't build a roll cage out of it unless that was a last resort, Mad Max sort of situation. And then I'd build it beefy.
Jim
Wow, this is an AMAZING wealth of knowledge! I'm going to be reading your posts over many times so I can absorb all the finite details.
Trip
PS. I'm also reading your other posts RE: welding.
Thanks for sharing your insights with me, everyone!