7018 Vs. 7018AC, Need Layman's translation please:

[Gary Fowler]

With regard to carbon steel quenching (one of several annealing processes) this quote from Wiki
"Generally speaking, cooling swiftly will give a finer pearlite (until the martensite critical temperature is reached) and cooling slowly will give a coarser pearlite. Cooling a hypoeutectoid (less than 0.77 wt% C) steel results in a pearlitic structure with α-ferrite at the grain boundaries. " Since most of the steel anyone on this site would be welding falls within this carbon steel content, this is what you would be doing. Pearlite has a much more elastic structure than normalized steel. Generally speaking, mild carbon steel cant to much in the way of heat treating and nothing is required for it unless it is welded in very thick (more than .75") sections. Then you need a PWHT treatment to relax the weld a bit. This is not something that you can do at home generally speaking as it requires the temp to be held at 1200-1250 F for 1 hour per inch of thickness and also a heating and cooling rate to note exceed 400F per hour above 800F. I dont think anyone can do that with a torch at home. We shouldnt be trying to weld spring steel back together as you are wasting your time. It will just break again. For most hobby welding using mild steel (A 36 plate and similar ) dont worry too much about damaging the steel, you are not going to hurt it.
For all you welders out there that occassionally have to take a bend test. When you cut your straps from the test coupon with an OA torch, let them drop directly into a bucket of water. This will transform the grain structure from coarse to small making them super ductile and bend like putty. This is more valuable to do as the tensile strength of the test coupon rises as in grade X 60 pipe and above. A 106 (mild Steel pipe similar to A 36 plate) wont be affected very much either way. Either way, there is no substitution for making a good weld Oh, dont do this with chrome / moly steels. They dont react well to sudden temperature changes.

 

[Steveguy]

In regard to the "lugging" conversation, I think you need to better define "lugging".
I would classify lugging an engine as running it at or near full throttle setting and then loading it so hard as to pull the engine downto a greatly reduced speed, at which the bearing loads are very high and the oil pressure has a hard time maintaining proper protection and can damage bearings.

Running an engine at reduced throttle settings and reducedengine speed also reduces power output, thereby reducing bearing loads. Done within reason, this is a safe and acceptable operating method. You do want to run enough engine speed so you have full oil pressure and enough power to do the work, (not idling around). I sometimes drive large farm tractors for my BIL and with the 375 HP track tractor, throttling back a couple hundred rpms does save on gallons per acre, which is the measure that matters. We do go over less acres per hour, but the labor works out cheaper than the increased fuel usage at full power. Important to note though is the engine is not being pulled way down by the load at either throttle setting.

 

[Shield Arc]

For all you welders out there that occassionally have to take a bend test. When you cut your straps from the test coupon with an OA torch, let them drop directly into a bucket of water. This will transform the grain structure from coarse to small making them super ductile and bend like putty. This is more valuable to do as the tensile strength of the test coupon rises as in grade X 60 pipe and above. A 106 (mild Steel pipe similar to A 36 plate) wont be affected very much either way. Either way, there is no substitution for making a good weld Oh, dont do this with chrome / moly steels. They dont react well to sudden temperature changes.

Gary that is a very interesting post, thanks! :thumbsup:
I've seem where people have posted that in a test situation where 10's if not 100's of weldors were testing. Say in the height of the nuclear power plant construction. Where completed test plates were dropped right in a tank of water, so they could be cut and bent right away. I've never seen this myself, have you, or even heard of it?

 

[rjmack]

For all you welders out there that occassionally have to take a bend test. When you cut your straps from the test coupon with an OA torch, let them drop directly into a bucket of water

we aren't allowed to do that... air quench only.

btw, the conversation regarding heat treatment was in regard to putting a hard edge on a brush hog blade. seeing as that's not going to happen with mild steel, it's pretty obvious we were talking about medium to high carbon steel as those are the steels that can be tempered. these steels are not softened or annealed by quenching from high temperature ranges.

 

[Soundguy]

Running an engine at reduced throttle settings and reducedengine speed also reduces power output, thereby reducing bearing loads. .

and if the work load doesn't change and the engine luggs.. you are gaining fuel economy at the cost of engine lifespan.

soudnguy

 

[gwdixon]

Please someone!!! Break this topic out into some subtopics as has already been suggested. Maybe even on a different forum on TBN.

7018 and 7018 AC have long been forgotten. Not complaining, just noting that 145 posts later it is wandering a bit.

 

[Soundguy]

reguardless if the original topic is long since gone.. it's still a quite usefull thread.

if certain posts bother you.. just skip them.

soundguy

 

[gwdixon]

reguardless if the original topic is long since gone.. it's still a quite usefull thread.

if certain posts bother you.. just skip them.

soundguy

You misunderstand. No bother at all. What I'd like is to be able to see threads that concentrate on one subject rather than a mishmash. It is far less confusing, is helpful to other members that might be interested in something buried in a unrecognizable thread, and it like earmarks in the Congress.

 

[Soundguy]

if there is a topic here your trying to follow.. go start a new post under that topic.. come back here.. and post a link to that post and ask the discussers' to join you..

best of both worlds...

soundguy

 

[Big Wave D]

I can see it either way, but personally I like the mish-mash, keeps your brain working and everyone on their toes. Helps to keep senility at bay.

I was the original poster, but don't really know how to separate the numerous running topics(how many are we up to 4,5 - oops there's that senility sneaking up again) that this thread now contains. A higher authority will have to parcel them out.

I've loved all the comments and food for thought that has been put forth.

KEEP 'EM COMING!!!