So why is carbon added to steel?
What benifits does having more or less carbon bring?Ji
…and why was chromium added, and why was molybdenum added and why was manganese added and why…
Alloy composition (by weight)
SAE grade % Cr % Mo % C * % Mn % P (max) % S (max) % Si
4118 0.40–0.60 0.08–0.15 0.18–0.23 0.70–0.90 0.035 0.040 0.15–0.35
4120 0.40–0.60 0.13–0.20 0.18–0.23 0.90–1.20 0.035 0.040 0.15–0.35
4121 0.45–0.65 0.20–0.30 0.18–0.23 0.75–1.00 0.035 0.040 0.15–0.35
4130 0.80–1.10 0.15–0.25 0.28–0.33 0.40–0.60 0.035 0.040 0.15–0.35
4135 0.80–1.10 0.15–0.25 0.33–0.38 0.70–0.90 0.035 0.040 0.15–0.35
4137 0.80–1.10 0.15–0.25 0.35–0.40 0.70–0.90 0.035 0.040 0.15–0.35
4140 0.80–1.10 0.15–0.25 0.38–0.43 0.75–1.00 0.035 0.040 0.15–0.35
4142 0.80–1.10 0.15–0.25 0.40–0.45 0.75–1.00 0.035 0.040 0.15–0.35
4145 0.80–1.10 0.15–0.25 0.43–0.48 0.75–1.00 0.035 0.040 0.15–0.35
4147 0.80–1.10 0.15–0.25 0.45–0.50 0.75–1.00 0.035 0.040 0.15–0.35
4150 0.80–1.10 0.15–0.25 0.48–0.53 0.75–1.00 0.035 0.040 0.15–0.35
4161 0.70–0.90 0.25–0.35 0.56–0.64 0.75–1.00 0.035 0.040 0.15–0.35
* The carbon composition of the alloy is denoted by the last two digits of the SAE specification number, in hundredths of a percent
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…I think Maico was pretty smart in their tube metal selection.Ji
Now I will preface this by saying that I am really not trying to be rude here [a bit frustrated, but not rude] - But if you don't understand the basic composition of steel alloys and how they affect the final material properties then how on earth can you make this judgement?
Were they [Maico] 'smart' or did they just use what was available locally in the right price range… none of this makes a single jot of difference as it is all supposition. The premise that manufacturers in the 70's spend copious time trawling the world looking for superior materials is just nonsense. Most were struggling to keep their heads above water with the coming Japanese onslaught.
I agree it is always good to expand your knowledge but this thread tries to fill in pieces of a jigsaw that is constantly redefined at will. It is bogged down with small pieces of information that alone make no real contribution to the answering of the original question.
If we are going to stress out [and make unsubstantiated claims] about a variation of 2% in the carbon content of our frames and how/why it varied then we need to get out more. Take a look at the above chart and you can see that the standard spec for 4130 allows for a 5% variation in carbon content - so the 2 or 3% variation found in the samples means absolutely nothing. Not significant - normal production variations - end of story. Not enough evidence to make these extrapolations.
So to summarise - if your frame breaks, send it to GMC [or the like] who will fix it using good old fashioned Aussie commonsense and hard earned practical experience. Listen to his advice [if he chooses to give it] and go and ride the thing.
If you want to fix it yourself then use the previously recommended welding rods and processes and see what happens. If it works then all is good, if not then try again. It is what GMC has done for years - it is why he is so good at what he does.
Round and round and round we go… where this stops nobody knows.
Ah, that feels better… [and far cheaper than therapy]
VMX42