Many car owners have heard such a sentence: as soon as a certain car arrives in China, it loves "aluminum for steel"
It seems that in everyone's concept, aluminum alloy represents the high-end atmosphere on the grade, and the steel plate is to cut corners and lack of heart.
A while ago, the off-road branch of BAIC Group released the news: BAIC's "off-road star" BJ40 model will usher in a replacement: a new B41V model will come out, using aluminum alloy girder frame! Thus becoming the only "hardcore passenger car with all-aluminum non-bearing structure" in the world...
To be honest, many people in off-road circles are very much looking forward to this car.
But here's the problem! "In the field of commercial vehicles", aluminum alloy girder frames are nothing new! Look at the mainland's Liuqi, Valin, Foton and other brands have long had aluminum alloy frame lightweight trucks.
And in the semi-trailer industry, there are many lightweight bulk and semi-trailer roads of all-aluminum alloy! ——Baiqi B41V actually transferred the technology played in the field of "commercial vehicles" to "passenger cars".
Aluminum alloy is more advanced than steel frame
Playing is the difference in weight-to-strength ratio
Speaking of which, do you still think that aluminum alloy material is a very tall thing in the automotive field, right? - Excuse me! Not really! However, who is more leather in aluminum alloy and steel, "commercial vehicles" have long given us the answer: aluminum frames can only be used for light-load purposes, and heavy-duty models are still the world of steel frames.
Many media and advertisements say that "aluminum alloy is stronger and lighter than steel". Is this a "business gimmick" or is it a real thing? - We have to start from the "weight-to-strength ratio"!
Commercial advertising, and most of the outside media outside the industry mouth of "new material strength is higher, stronger than iron than steel", in fact, is said to be "weight strength ratio"! So what is the "weight-to-strength ratio"? - Let's say: use iron and aluminum bars of the same length (such as 50 cm) and stipulate that they weigh the same (let's say, 5 grams).
In this case, the diameter (thickness) of the iron bar may be as thick as the thread of the sewing clothes (perhaps more appropriately called "wire"),and the diameter of the aluminum bar may be as thick as a toothpick. Then you test the tensile ability of these 2 metal bars and find that under the same size of tension, the wire is broken, while the aluminum strip is not broken. So you come up with the theory that "aluminum is stronger than iron."
The above is the "weight-to-strength ratio" - in the case of equal weight, see which material is stronger - commercial advertising, and most of the outside media do it! Because the specific gravity of iron is 7.9 g/cm, while aluminum is only 2.7 g/cm! Iron is 3 times heavier than aluminum density, so aluminum strips are 3 times thicker than wire! - Of course, the wire suffers!
By volumetric intensity ratio
Steel can press aluminum to the ground and rub it
But when it comes to the field of industrial machinery, this is not the case at all! Because the industrial field says more about the "volume-to-strength ratio". According to the tensile strength standard test method of industrial materials (common at home and abroad), the specific comparison of the two materials is "who is strong and who is weak":
Use a "small sample" of the same length of 2 materials (let's say everyone is 10 cm), then specify the same diameter thickness of both (let's say 1 mm), and then go up the tensile test machine. The pull is constantly increased until the "sample" is broken. The instrument automatically records the maximum tensile force value. - This is the "volume-to-strength ratio"! Different materials, thickness, thickness the same, see who is stronger!
As far as the current situation is concerned, according to the most common "volume strength ratio" in the industry, the ultimate strength of ultra-high-strength steel can exceed 2GPA (that is, 2000MPA, such as the famous "300M steel" used to manufacture aircraft landing gear); and the current highest strength level of 7075 aluminum alloy, after heat treatment, the ultimate strength after heat treatment and drawing is only 500MPA. Exactly 4 times worse than steel!
So this so-called aluminum is better and stronger than steel, just like you and Tyson are stronger than who.
If you want to win, you can't fight with him, you have to go to your own strengths to be weaker than each other, so many media mouth an aluminum stronger than steel every day, which is the truth.
Cars made of aluminum are meant to reduce weight
Simply can not afford to use composite materials to choose aluminum
Automobile production field: The steel used to make automobile girders and skeleton structures is usually made of high-strength steel
The strength level is usually above 550PMA (now truck frames are at this level), and even ultra-high-strength steel above 780MPA is used.
The aluminum alloy widely used in the skeleton structure of automobiles is 6061/6063 series high-toughness aluminum alloy (2024 and 7075 high-strength aluminum alloys are too hard to stamp). The ultimate strength of the 6061/6063 series aluminum alloy after heat treatment is only 300MPA level!
In terms of strength indicators, basically aluminum alloy is about 2 times worse than steel. This means that the thickness of the aluminum alloy structure should be 2 times thicker than the steel plate to ensure the same robustness of the structure. But the problem is that the advantages of lightweight weight reduction are actually smaller, less obvious.
And a lot of advertising and so-called popular science bloggers will never tell you
Aluminum alloy inherent fatigue resistance is much worse than steel, so the life of the aluminum alloy stress structure is much lower than that of steel. When encountering sudden and violent impacts, aluminum alloys are more likely to produce cracks, further aggravating component damage, while steel plates are known for their high toughness, often only dented and deformed after being subjected to violent impacts.
For cars and home SUVs, the use of aluminum alloy structure can fully meet the needs of use, while also slightly lightweight.
But for hardcore off-road vehicles, such a little bit of lightweight in exchange for a double decline in strength and volume, put cheaper and higher strength steel is not used, you have to use anti-torsion is not so strong aluminum alloy "stacking", is not a little too strong, right?
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