Hardness is one I guess? Cheap Chinese Aluminium is little softer?
Same question for steels too.
- if they make it local, it costs less. less labour costs, less electrical power costs, less shipping costs. the same reasons alot of things in china are less money.
- they get heavy subsidies.
as for quality, its hard to say, if they are meeting the spec for the alloy as mentioned above, it should be fine. if you had the ability to test it somehow, you could get them to send you samples. were used to chinese companies skimping on quality due to low skill labour or cheap materials, but its hard to really skimp on something like an aluminium bar.
and... $15/kg more? its only $4/kg for 6061 here in canada.....
Aluminium needs a huge amount of electricity. Thus Chinese aluminium will be more poluting and probably putting more co2 n to the air (if made from cal)
1. Chinese labor is, for the moment and foreseeable future, significantly cheaper. 2. Chinese power, being unregulated and not subject to the same strict environmental regulations that the west is, is cheaper.
3. Mining the raw materials in China is cheaper.
4. There are NO labor laws in China. (think Lao Gai)
1+2+3+4=A lot cheaper.
But the question wasn't cost, it was quality, was it not?
When I think Chinese quality, I think lack of. Like gluten, drywall, machine tools, everything Walmart. It's crap. It's Made In Japan 1960. But the big difference between those two is that China lies about everything.
They'll say it's +/-.005, but when you measure it, don't be surprised if it's not....if you get my meaning.
international metal cross reference from the book Jianming Wujin Shouce is attached
picture of page 1061 showing ASTM 6061 aluminum alloy and cross reference numbers for Chinese, UK, Russian, Japanese, USA, France, German, and a few i am not sure about.
since most Chinese Engineers can read and write many languages i would think most Americans can easily read this and understand all the world wide metal alloys numbers and their differences.
also i would think all American machinist should be able to open their copy of the Jianming Wujin Shouce or equivalent and look up world wide metal alloy standards themselves in 5 minutes or less. most Chinese Engineers i know can do this, it was part of their 1st year Engineering education.
Your point is well taken, and noted that you've been harping on this for over a year, anyway.
Maybe the engineers you've talked to were well educated, and I wouldn't question that. From MY personal experience, dealing with their scientists in U.S. schools the breadth of knowledge is, to say the least, from one extreme to the other.
My point was, and remains, is that despite knowing what the specs are, the delivered product can vary dramatically from the advertised.
On the issue of American machinists keeping up with their competition, I'll have to concede. We're losing ground, and THAT'S not their fault.
It's easy to answer, they will say you that their alloy, aluminum or steel or stainless meets the metallurgy standard but this is not true.
We have a company near my shop where they make stainless steel drum made from 304, laser welded with Fanuc robots, they bought some drums from China which they said was made with 304 but when you put a magnet on it, is stick on it and you could see rust on some joints.
The alloy did not meet the standard for 304 stainless and you could see the difference in color and quality.
Just look at casting quality, nothing to compare with others.
1) in China the best way to get the metal alloy you want is to ask for a Government Stamped Receipt with metal spec. Takes about 5 minutes to get spec faxed over and store to stamp a receipt. You will pay sales tax and more for the certified stamped receipt. If they do not give you what you have a stamped government stamped receipt for they can go to a Chinese jail for a long time. It is been my experience they will not mess with the government.
2) Chinese 304 Stainless is often what we call 321. And welding rod needs to be for 321 or welds will not be correct. Often their is confusion in a customer buying Chinese 304 (ASTM 321) thinking it is ASTM 304. Improperly used ASTM 321 if welded with ASTM 304 can sometimes cause problems.
........ Translation errors can cause big problems sometimes. Once a Chinese Engineer explained it to me I adjusted my buying practices by learning more about what I was actually buying. The problem was originally my ignorance of Chinese metal standards more than anything else.
3) In China go to any 4 star or higher hotel and at the bar you will see many experts from all over the world. Standing shoulder to shoulder with German, Swiss, American, etc experts I have seen many a American get their pride bubble burst after they realize their competitions experience and education level. Sometimes it takes months or years but eventually the Americans realize they are not the most important manufacturing country in the world. They haven't been for many decades now.
About those stamps, I saw a kid in a market stamping "silver" jewelry with a "government" proof mark.
people will lie to make a buck, its not limited to political boundaries.
as mentioned above, in china, much like in the US, if you lie about aerospace materials, the concequences are much more dire than on cheap consumer trinkets.
there is only one way to get what you want from any company in any country, communicate, inspect, and be prepared to pay fair value. if you are trying to force a companies employees into poverty to sell your junk to wallmart at rock bottom prices, then id be not surprised in the least if they provide a sub expectation part, or even mess with you out of spite.