When you're welding steel and aluminum, how does the heat change the structure of the metal in general, if at all? Is the change permanent? How would the structure change if you quenched it rather than letting it cool slowly? What affects are produced by each?
>>7724846
>look it up
>from a phase diagram
As molten iron cools it crystallizes at 1538 °C into its δ allotrope, which has a body-centered cubic (bcc) crystal structure. As it cools further to 1394 °C, it changes to its γ-iron allotrope, a face-centered cubic (fcc) crystal structure, or austenite. At 912 °C and below, the crystal structure again becomes the bcc α-iron allotrope, or ferrite. Finally, at 770 °C (the Curie point, Tc) iron becomes magnetic. As the iron passes through the Curie temperature there is no change in crystalline structure, but there is a change in "domain structure", where each domain contains iron atoms with a particular electronic spin. In unmagnetized iron, all the electronic spins of the atoms within one domain are in the same direction, however, the neighboring domains point in various other directions and thus overall they cancel each other out. As a result, the iron is unmagnetized.
>>7724857
I don't care about iron or magnetism, m8
>>7724864
what is steel without iron?
>just carbon
>>7724846
>how does the heat change the structure of the metal in general
in general, for the worse
although a well done weld won't fail, the area surrounding it will because of the heat that it receives
>Is the change permanent?
unless you do something about it, why wouldn't it be
>How would the structure change if you quenched it rather than letting it cool slowly?
becomes harder but also more brittle
>>7724864
Go look at an isothermal diagram. How far below the eutectoid point did you go and for how long did you hold it to that temperature? Did you quench it when it was in a pearlite, bainite, or austenite phase.
>>7724873
More like what is steel without carbon
But, surely the presence of carbon in the alloy changes the effects of heat treatment.
>>7724890
so it's compression and tension strength would be higher, but it's shear strength lower?
or is hardness not at all related to acting forces?
>>7724911
whether or not hardness is altered depends on if the steel has been heat treated / hardened or not
>>7724911
>or is hardness not at all related to acting forces?
no
it's an indicator for overall tensile strength, but more importantly for the ratio of deformation to tension
the harder the material the less it deforms under stress
downside to the increase in tensile strength is that when it fails it will also fail more abruptly instead of being bent
https://www.youtube.com/watch?v=GNvmh2ZrKlg
>>7724945
Right I realized that after I typed it my bad.
yield strength is the same, but it's plasticity characteristic will be different.
I think the welded parts, which are not fused very well on smaller scale would break if quenched, since the welded and the non-welded metal have a different expansion time.
I think it is technically very hard to cool only the welded metal.
explosion welding is a pretty effective approach which give a nearly perfectly interlocked weld pattern, I saw a docu about it and was amazed at the precision of this brute force process
pic related
>>7724968
said weld pattern
could be art
Read Smith's, Askeland's ,Shackleford's books on materials
>>7724968
I watched a video where two steel tubes where welded together in a jig to minimize heat distortion, but because the end of one of the tubes had a spherical bearing there was still some binding afterward due to distortion.
So what the guy did was take it out of the jig, heat the area around the bearing with a propane torch, and then quench it with compressed air.
This let the spherical bearing move freely again, reversing the distortion, but I have no idea how.
The other reason I was asking was just a general curiosity as to how quenching would affect strength.
>>7724994
did he heat it with the torch manually?
if yes that will have a influence on the quality of the weld
do you have the link?
>>7725010
https://www.youtube.com/watch?v=AKJgO-Y5NX4
>>7725096
he relaxes it at the end, 4:10
>>7725105
I dont know either maybe they heated and cooled the air inside?
>>7724846
Bin a few decades, when you heat and cool, the alloying elements in the metal disperse and change size. The most notable of which is the carbon, which can divide into smaller more evenly dispersed lumps making the steel harder (and more brittle).
