What is Hot Short?

I don't know about steel alloys , but it has a different meaning with aluminum . With aluminum hot short is just short of melting , and the aluminum becomes very easy to break up , broken surfaces have a very grainy appearance .

I think I have heard it in reference to 7075 aluminum as well. 7075 is "generally" not considered to be easily weldable, but it can be welded by some types of laser welding... being a parrot here of things I have heard. I didn't want to throw to much in there that could be wrong so as hopefully to avoid arguments over my factoids and get more towards the point.

"I don't know what you are asking, but if you provide enough background information I'll find a tangent to argue about." LOL. No accusation there of course.

The term was originally used to identify the tendency of some metals to become brittle when heated - usually red heat in steel alloys.

I believe it is now also used to identify the tendency to crack from welding in certain metals.

It was a term used in the Sheffield steel industry I started in.

• As I understand and recall it * (caveat) The term "short" meaning brittle or fractures has a general meaning. eg. "shortbread" - which as a type is a biscuit / cookie which has the property that it fractures readily if you apply a bending force to it ie. "hot short" and "shortbread" have the same meaning to the "short" in the name. Different meaning to dimension in this case.

"hot short" means if you work the metal while hot, seeking malleability (not specifically ductily, which more relates to "cold" wire-drawing), you don't get malleability because the metal cracks and/or fractures during that hot-working. Where you would otherwise look to the metal deforming in a forming process with result of forming some useful product.

Hot-shortness can be caused by solutes in the metal which form low melting point phases which do indeed melt during what would otherwise be a useful hot-working process. Segregation of non-metallic / semi-metallic impurities to grain boundaries could be another mechanism causing hot-shortness. etc.

It was a term used in the Sheffield steel industry I started in.

• As I understand and recall it * (caveat) The term "short" meaning brittle or fractures has a general meaning. eg. "shortbread" - which as a type is a biscuit / cookie which has the property that it fractures readily if you apply a bending force to it ie. "hot short" and "shortbread" have the same meaning to the "short" in the name. Different meaning to dimension in this case.

"hot short" means if you work the metal while hot, seeking malleability (not specifically ductily, which more relates to "cold" wire-drawing), you don't get malleability because the metal cracks and/or fractures during that hot-working. Where you would otherwise look to the metal deforming in a forming process with result of forming some useful product.

Hot-shortness can be caused by solutes in the metal which form low melting point phases which do indeed melt during what would otherwise be a useful hot-working process. Segregation of non-metallic / semi-metallic impurities to grain boundaries could be another mechanism causing hot-shortness. etc.

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I've read that at the time Titanic was built the sulfur content was considered acceptable as long as the steel didn't show hot shortness. At the time they had little experience with brittleness when cold.

Every aluminum alloy I've melted down for casting stock has exhibited this characteristic , in fact I rely on it . Especially with stuff like alloy wheels/rims , that are too big to process any other way . Lay that sucker down on a nice hot hardwood fire and when it starts looking like it's about to melt (there are signs if you recognize them) start dragging chunks off with a pair of blacksmith tongs . I usually have a preheated crucible on standby in the foundry furnace to receive them . Wheel to crucible to ingot mold to out of my way while it cools . Speaking of casting , I've got a brand new .452/255gr bullet mold in desperate need of some molten wheel weight/pure lead alloy ... I was thinking .45 ACP when I bought it , but a couple of neighbors have 1873 SAA replicas . They currently use them for fast draw competition , but they're easily repurposed if the need arises .

I think most of the "casting" alloys probably exhibit some of this. I have found no real issue with welding 5052, 6061, or 3003 other than my general lack of skills. I've also heard 6061 is particularly poor for casting unless you increase the silicon metal content. I have several pounds of silicone metal on the shelf for such experimentation "someday." I am concerned about its higher melting point, but I've been told it will dissolve at aluminum casting temperatures. I've also heard you can "cast" 6061 under high pressure with rapid cooling and not get the crystallization it exhibits when gravity cast and "normally" cooled. Of course this is a tangent.

Shoot , I toss out a perfectly good rabbit hole and you totally ignore it ... I don't usually melt any aluminum but cast alloys .

Did thumbody thay wabbit? Wewes that wabbit?

I generate more 6061 scrap than is reasonable. I've been told recyclers won't pay much for it, so finding ways to entertain myself with it... I make a lot of racks and brackets out of the scraps. The tool racks on all of my CNC machines are made from scrap aluminum. The top/outside often looks okay, but if you look at the other side you often find a failed mold machining. I only need "so many" tool racks. One of my reasons for wanting to learn more about ways I might weld 1/2in and thicker 6061 is rooted in finding other ways to reduce this pile that is slowly coming to life and devouring my shop like the killer tomato that ate New York City.

As an aside when I was just making a few molds for myself on my Taig CNC mill I tried to weld in miscuts while they were still on the table. It was never pretty, but I did miraculous save a few piece of metal. The other miracle is I didn't fry the controller for the mill.

My question about hot short doesn't really relate to 6061 or 5052 though as those weld okay if you have the skills and the equipment.

There's a 5000-series casting alloy? Is it good? What is it good for? I was thinking of marine / yacht applications... (I am familiar with "LM25" / "A356 Al-Si-Mg)

That is interesting. Also confusing. Some while back I started using

1144 for some tools and parts because of its combination of modest strength properties and machineability. Its been referred to as having hot short properties when attempting to weld. I have not tried to weld it, but I have done simple forging with it. The last project was a handle for a slide lock drill press vise I built as a gift for a family member. The handle was a simple piece of 1144 rod with the ends upset and forged into a ball after being slid through the meat ball. (more of a bell shape really) I had run across an old thread on a forum named iforgeiron that seemed to indicate it was forgeable. I didn't really have any issue other than the generally harder hammer blows required with medium carbon steel over mild steel when forging at a medium red heat. (Didn't want to overheat and risk decarburizing it.) Maybe I just didn't get it hot enough to be an issue?

Riveted, if a plate broke it couldn't propagate beyond that plate. I think they got cracked plates in those days, but you could rivet in another. ie. consequences very low. Welded - it would be a disaster with a crack ripping around the hull. Then there was cost. These days Western European steels are "blown down" to very clean, lean and ductile. I measured the yield-stress of an S355 (50ksi - A572Gr50) Structural Hollow Section and got 360MPa. The control is so exact. Not what they had then.

I think ATP5 (cast aluminum tooling plate) is a 5000 series alloy. Generally I like it better for fixtures than MIC6 which I believe is a

7000 series cast aluminum tooling plate. I think I read somewhere that ATP5 is weldable, but its been a while. I could be mistaken.

Honestly for smaller fixture plates I really don't have much issue using

6061 wrought flat bar if I have some of a suitable size on hand.

The silicon will dissolve in the molten aluminium in the same way the sugar dissolves in tea or coffee. I wondered once how they make modern pewter (Britannia metal) which is usually 92/6/2 tin/antimony/copper as copper has a much higher melting point than tin and it was explained that it dissolves. It's the reason good soldering iron tips are iron plated as iron is virtually insoluble in tin whereas copper is quite soluble and I've seen the results with cheap soldering iron tips degrading in use for that reason.

From the sound of your description you may have heated it to above the solidus temperature for the alloy in which case some of the alloy constituent phases will be molten and act as you describe.

I never got into the science of it , I just know that aluminum has a phase just short of melting where it's really really easy to rip chunks off . Here's a link describing what you just said (I think ...)

Might help Bob with his query about hot short too ... FWIW I keep 4043 , 5356 , and 4047 filler on hand . The only time I had a problem with an aluminum weld was when I repaired a cracked cast motorcycle part . Damn thing cracked at the weld as soon as the mechanic started tightening the bolts . Fortunately for me the replacement part cost just a few bucks less than I charged for the repair ... I got paid with experience for that job .

I'll not comment, other than I believe all 5000-series are weldable.

Well, the ATP5 I have is all 1 inch (25.4mm) or thicker. Its not weldable by me. LOL.