4140 need not be heat treated unless you desire the properties of the
hardened material, one of which is greater strength. Hardness is yet
another of the features that are improved. Hardness relates to tensile
strength, so the harder the material is drawn, the stronger it becomes, but
at the expense of ductility.
4140 is available in a heat treated condition, and is still quite
machinable, or it is available in the annealed condition, so it can be heat
treated at the appropriate time, to exacting specifications.
1035 doesn't become 4140-------or anything else------not when it's heat
treated. All it does is get harder, there are no chemical changes in the
material. It is also borderline too low to heat treat because of its low
4140 is what it is because of the presence of specific elements, namely
carbon, manganese, phosphorus, silicon, sulfur, chromium and molybdenum, in
very specific quantities to develop the desired qualities. The numbers
applied to steel alloys are not random-----each one has a specific meaning,
and tells you what family of alloy you are dealing with. The last two
digits are the percentage of carbon in the alloy, in hundredths of a
percentage point. Therefore, 4140 contains .40% carbon. The designation
41 implies that the alloy is in the chrome-molybdenum family----along with
4130, 4142, 4145, 4150 and perhaps even more.
There are some excellent stock books that can provide the chemical makeup of
various alloys. I suggest you contact a steel distributor and ask about
4140 doesn't have to be heat treated unless it is required , 4140 is a
Chromium and Molybdenum alloy that has a Carbon content of approx. .40 % or
40/100 of 1 % and responds well to heat treat for hardening , 1035 is just
common steel without the alloys and it has a carbon content of .35 or
35/100 of 1 % and could be hardened , the steel that you have in your
toaster , car fenders and refrigerator is plain 1010 to 1020 steel , heat
treating does not appreciably change the alloy content , I have had to weld
4140 on occasion and the extra 1/10 th of a percent carbon as opposed to
4130 can make for a real headache , probably you should get a book on metals
and do some reading , really too much information to get off this site .
I made the replacement tailspring on my taildragger aircraft out of
4140....maybe 4 years ago now.
heat treated and tempered correctly (well approximately correctly) it
makes a superb spring steel. temper to 180,000psi UTS for a spring.
What the others said about material composition. If you are just looking
for the answer without delving into how it gets there, take a look at
search on '4140' or '4130' or what ever, pick out a standard size that
makes sense to you (say 1" round stock) take a look at the different
properties when heat treated differently. The composition stays the
same, the tensile, yield, and ductility are all over the map.
4140 typically comes in either annealled (softest) or normalized
(somewhat harder) to allow reasonable machining and fabrication. The the
final assembly is heat treated to whatever specs are needed.
One application where the 4140/4130 is not heat treated is in assemblies
used for extremely cold temps (-40F). The chrome/moly allows have a MUCH
higher resistance to impact (Charpy test) at these temps than mild
steel. Think snowmobiles at -40F and 80 mph on a frozen lake. It's nice
if the front suspension doesn't shatter on an ice ridge.
Weird Al Perkoffovic wrote:
In addition to Harold's excellent answer I would add this: for most
aplications 4140 is heat treated because you can! If you only need the
properties of anealed 4140, why spend the money for all the extra alloying
elements? As was said in other posts, heat treating 1020 or 1035 doesn't
buy much in material properties. Of course, there are always exceptions to
every generalization, but the basic reason 4140 is usually heat treated is
because it can be heat treated to get the desired properties.
Hope this helps.
Responding to responses will let us know that you're actually listening.
Assuming you mean steel, the number just specifies the alloy. How you
heat treat is is a private matter between you, your heat treating shop,
and your materials engineer if you have one.
I have a book, "What Steel Shall I Use". It was written in the 1940s,
before engineers were assumed to know this stuff, so it's actually in
something close to english and covers all the basics. The guy goes into
the meaning of the numbers, why 1050 may be as good as 4140 for you
(cheaper to buy, but more expensive to heat treat reliably), and other
I'd recommend getting it, but I have no idea how easy copies are to
find. Instead, look for a good web site that goes into alloys and heat
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