'Bed angle iron' welding

My friend has 200 used hospital beds that have 2 pieces of angle iron each (about 6' long after removing the ends). Off hand I believe this angle is
about 1.25" x 1.25" x 1/8". It is that type of iron that is next to impossible to drill. Harder than heck. But not brittle (yet). My friend has hopes of using this angle to fabricate trusses to span 32 feet. Using 1/4" plate gussets to hold the trusses together. Each top and bottom chord will have a minumum of two angles with the gusset sandwiched between. Legs (no longer than 30") in compression will have a 'stabilizer' in the middle. At not time will a bead be placed across the angles. All beads will be on the long edges. Is there any safe way to weld this hard angle to the hot rolled plate brackets? ****************************
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Bad Idea Department IMHO
The 'hard to drill' steel needs to have a reasonable to large amount of carbon, figure 1045 to 1060 steel (.45% to .6% carbon). When you weld it, you get a HAZ (Heat Affected Zone) that has a thin layer of highly quenched high carbon steel. This layer has extremely high tensile strength and a yield point that is very close to the tensile. NET: It's not ductile, snaps suddenly under load.
Welding this material to mild steel means that the mild steel will be ductile and move to push all the stress into concentrated spots in the angle iron.
Worse is that all of these effects are not consistent. If you hold the stinger on a spot for a second longer, it will be quite different from one in the middle of a longer bead.
And you are planning to use this for an overhead truss where things might fall down on someone's head? OK, at least you are not planning to build a utility trailer subject to lots of bouncing and fatigue issues.
On 3/8/2011 4:57 PM, Pintlar wrote:

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RoyJ wrote:

Yeah, I agree - bad idea. I used to use OBF a lot, until I had joints that basically fell apart because they were so brittle.
I hope that your friend didn't pay anything for them. The scrap value wouldn't cover the trouble of hauling them around.
Bob
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size=2 face=Arial>...</FONT></DIV> <DIV><FONT size=2 face=Arial>&gt; Bad Idea Department IMHO<BR>&gt; = <BR>&gt; The 'hard to drill' steel needs to have a reasonable to large amount of <BR>&gt; carbon, figure 1045 to 1060 steel (.45% to .6% carbon). When you weld <BR>&gt; it, you get a HAZ (Heat Affected Zone) that has a thin layer of highly <BR>&gt; quenched high carbon steel. This layer has&nbsp; extremely high tensile <BR>&gt; strength and a yield point that is very close to the tensile. NET: It's <BR>&gt; not ductile, snaps suddenly under load.<BR>&gt; <BR>&gt; Welding this material to mild steel means that the mild steel will be <BR>&gt; ductile and move to push all the stress into concentrated spots in the <BR>&gt; angle iron.<BR>&gt; <BR>&gt; Worse is that all of these effects are not consistent. If you hold the <BR>&gt; stinger on a spot for a second longer, it will be quite different from <BR>&gt; one in the middle of a longer bead.<BR>&gt; <BR>&gt; And you are planning to use this for an overhead truss where things <BR>&gt; might fall down on someone's head?&nbsp; </FONT></DIV> <DIV><FONT size=2 face=Arial>*********************&nbsp;/ / / / / / / / NOT ANYMORE/////////////////////*****************</FONT></DIV> <DIV><FONT size=2 face=Arial>OK, at least you are not planning to = <BR>&gt; build a utility trailer subject to lots of bouncing and fatigue issues.<BR>&gt; <BR>&gt; On 3/8/2011 4:57 PM, Pintlar wrote:<BR>&gt;&gt; My friend has 200 used hospital beds that have 2 pieces of angle iron each<BR>&gt;&gt; (about 6' long after removing the ends). Off hand I believe this angle is<BR>&gt;&gt; about 1.25" x 1.25" x 1/8".<BR>&gt;&gt; It is that type of iron that is next to impossible to drill. Harder than<BR>&gt;&gt; heck.&nbsp; But not brittle (yet).<BR>&gt;&gt; My friend has hopes of using this angle to fabricate trusses to span 32<BR>&gt;&gt; feet.&nbsp; Using 1/4" plate gussets to hold the trusses together.<BR>&gt;&gt; Each top and bottom chord will have a minumum of two angles with the gusset<BR>&gt;&gt; sandwiched between.<BR>&gt;&gt; Legs (no longer than 30") in compression will have a 'stabilizer' in the<BR>&gt;&gt; middle.<BR>&gt;&gt; At not time will a bead be placed across the angles.&nbsp; All beads will be on<BR>&gt;&gt; the long edges.<BR>&gt;&gt; Is there any safe way to weld this hard angle to the hot rolled plate<BR>&gt;&gt; brackets?<BR>&gt;&gt; ****************************<BR>&gt;&gt;<BR>&gt;&gt;</FONT></DIV></BODY></HTML>
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Pintlar wrote:

Rivets?
http://www.youtube.com/watch?v=I9Q5OHYDbvo&feature=player_embedded

--Winston
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Or perhaps bolts? --Glenn
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Glenn Lyford wrote:

I guess that wouldn't be too exotic. :)
How about brazing? http://www.welding-technology-machines.info/brazing/brazing-joint-design.htm
--Winston
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Still going to have issues with the base metal. Heating it red hot to braze will pull the temper of that section, making it relatively soft and certainly more ductile. The transition zone will be ill defined, hard to figure out what the structural issues will be.
On 3/9/2011 8:01 AM, Winston wrote:

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