Tensile strength

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We all know that "60xx" is 60k psi, and "70xx" is 70k psi.  I have always wondered what mig and flux-core rates?
Reply:with mig it is 2-3 numbers as well. ER 70 S-X the 70 is 70,000 with flux core E 7 1 T- X the 7 is multiplied by 10,000 to give you 70,000 as well.
Reply:What is really interesting are discussions about the advantages of tensile stregth vs. ductility.The weld can be very strong, but brittle in relation to the parent metal, let's say A-36.I know very little about it, but I wonder if the high K tensile strength makes up for the relatively small cross section of the weld in relation to the shape welded ie. beam, channel, etc.I dunno"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Originally Posted by JC'sWeldingWe all know that "60xx" is 60k psi, and "70xx" is 70k psi.  I have always wondered what mig and flux-core rates?
Reply:What about the Lincoln NR-211-MP .035 flux core?
Reply:Certain wires are labeled according to industry standards, and others aren't.  But the properties are the same.  Weldmark is one example.  It's a weird designation, but according to what they say.....it measures up.  Sometimes I wonder if the claims are real.I think they have to meet AWS standards, but I'm out of my depth on that one"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Originally Posted by JC'sWeldingWhat about the Lincoln NR-211-MP .035 flux core?
Reply:Originally Posted by JC'sWeldingWhat about the Lincoln NR-211-MP .035 flux core?
Reply:I always wondered why on earth we weld 40k steel with 70k rod or wire.  Just give me somethin ductile and I'll be happy.
Reply:Sam,When it comes to strength, a weldor should match the filler metal to the base metal; a little higher strength filler metal is OK.  Lower strength[then the base metal] filler metal is not.A36 steel has a minimum strength of about 40,000 psi (40 KSI).  So E60XX, E70XX, ER70, or even ER80 class filler metals are OK.  Anything higher strength and you run the risk that the weld is so much stronger, and less ductile, than the base metal that there will be problems.High strength fillers will expand and contract at different rates than ordinary structural steels, like A36.  So if you weld A36 with E110XX rods, the weld will contract as it cools, and the different expansion/contraction rate between the metals will put the weld under a terrible stress.  In fact, the weld may tear away from the base metal entirely, as it cools.There can also be problems with the metal chemistry when mis-matching occurs.  The molten metal chemistry is a mixture, an average of the chemistry for the base metal and the filler metal.  High strength filler metals have added alloying ingredients to achieve that strength.  When those metals are diluted by welding with lower strength base metals, which are mostly composed of iron, the resulting weld metal can have undesireable traits.  There are certain chemical compositions that are vunerable to cracking while cooling, for example.  When you mix high and low strength steels through welding, the weld metal can wind up having these 'bad' combinations of chemistry.The same is true when welding high strength base metals, like A514, AR500, 4130, or Manganese steels, with low strength filler metals.  Not only is the joint lower in strength when you do this, but you can wind up with hot cracking problems because the chemistry that results in the weld metal is 'bad'.These problems become all the more likely when you start working with stainless steels, which have high amounts of alloying elements in their mixes.For most of the general fabrication work, the kind of repair work I see you posting about, you don't need to worry much beyond matching the strength of the weld to the base metal you're working with.  For structural steel, or say pipeline on the seabed, or in the Arctic, the designers need welding filler metals that can stay strong at low temperatures, or withstand a lot of bending without failing.  The weld metals rated for impact, at low temperatures, are custom tailored to meet these needs.  In the most general terms, they are more expensive because they'll undergo more testing in development and closer monitoring during the filler metal manufacturing process.  They may also be more difficult to weld with, because compromises are made between mechanical properties and ease of use(what we call 'weldability' for short).I believe the original reason that filler metals are always a little stronger than the base metal is that the code designers assume there are always going to be some defects in a weld.  Gas pockets, inclusions, undercut, etc.  The higher strength filler metal ensures that the joint will be sound even if the weld isn't 100% perfect.  This in no way should make any weldor do less than strive for the perfect weld every time they work, because you never really know what the margin of safety is when you're welding 2 pieces of metal together. Originally Posted by farmersammYou really got me to thinking.I was leafing thru a Lincoln guide to their wires, and it was confusing.Various wires were rated at 70,000 psi, but with caveats.  Not valid for seismic regions, not Charpy test valid, etc.  Wires seem to be pretty across the board.  I'm not sure how one goes about selecting a good wire for the application.
Reply:Originally Posted by farmersammYou really got me to thinking.I was leafing thru a Lincoln guide to their wires, and it was confusing.Various wires were rated at 70,000 psi, but with caveats.  Not valid for seismic regions, not Charpy test valid, etc.  Wires seem to be pretty across the board.  I'm not sure how one goes about selecting a good wire for the application.
Reply:Originally Posted by DSWE71-T11 is what lincoln lists that wire at. The NR-211-MP is just Lincoln's product designation. That makes it a 70K wire.http://www.mylincolnelectric.com/Cat...et.aspx?p=5853
Reply:I believe it's 1 cubic in. of 70s is equal to 70,000 lbs.
Reply:I believe it's 1 cubic inch for 70s is equal to 70,000 lbs                 revpol
Reply:Stress-Strain goes like this.Stress; thousands of pounds per square inch of cross sectional area.Apply a 2,000-pound force perpendicular to a 1 x ½ inch face.2,000/ 1x1/2 = 2,000/ 0.5 = 4,000 pounds per square inch. Strain; elongation per unit length. Inches/inch of length.Apply a force in tension to a 12.000-inch long rod. The rod is starched to 12.012 inches.The change in length is [12.012-12.000] or 0.012 inches. The strain is 0.012/ 12.000 = 0.001 inches per inch of length. Problem; what is the required tension force to load a beam 4” x 6” ten feet long to a stress of 9,200 lbs. per square inch, and how much will it stretch?Force = stress x area 9,200 x 4 x 6 = 220800 lbs or 110.4 tons.Stretch = elongation per unit length x length.0.001 x 10 x 12 = 0.12 inches
Reply:Originally Posted by transitStress-Strain goes like this.Stress; thousands of pounds per square inch of cross sectional area.Apply a 2,000-pound force perpendicular to a 1 x ½ inch face.2,000/ 1x1/2 = 2,000/ 0.5 = 4,000 pounds per square inch. Strain; elongation per unit length. Inches/inch of length.Apply a force in tension to a 12.000-inch long rod. The rod is starched to 12.012 inches.The change in length is [12.012-12.000] or 0.012 inches. The strain is 0.012/ 12.000 = 0.001 inches per inch of length. Problem; what is the required tension force to load a beam 4” x 6” ten feet long to a stress of 9,200 lbs. per square inch, and how much will it stretch?Force = stress x area 9,200 x 4 x 6 = 220800 lbs or 110.4 tons.Stretch = elongation per unit length x length.0.001 x 10 x 12 = 0.12 inches
Reply:Come on JC, this is the simple stuff. That ER70S-6 or E 6013 rod you use, where do you think the 70 and 60 comes from. The 70 is 70,000 pounds per square inch tensile strength. A rod 1/2 inch by 1/2 inch has a cross section of 0.25 square inches. 70,000 lbs/ square inch x 0.25 square inches = 17,500 lbs. meaning you could pull/ support/ hang a load of 17,500 pounds.
Reply:Come on JC, this is the simple stuff. Attached Imagesstress-strain.pdf (17.3 KB, 14 views)
Reply:Don't worry JC, Stress stain diagrams and all had me a bit confused even back when I could still remember my engineering classes.Think of it this way.. Stress is in PSI. You can think of it like the gas in your gas bottle. at 1200PSI the gas in the bottle exerts 1200 lbs of force on each inch of surface area of the bottle. The bigger the area for the same "weight" (force) the less likely it is to bend or yeild. why you sink in mud, but can stand on top of it if you put down a sheet of plywood 1st. Same force, larger area so less stress.Strain is stretch. If you hang a weight from a 1' bungee it will stretch X length. If you hang the same weight from a 2' bunge it will stretch twice as far. Make sense?transit I think part of what may be confiusing in your strain example is the I believe you are using constants that are not explained. IE steel would stretch less than the bungee and there fore have a different constant to be multiplied to the Inches/inch of length.
Reply:True, however I’m trying to use terms and values JC would be comfortable with for metal. The numbers for wood and concert would be way different, the principles being the same.Last edited by transit; 06-21-2009 at 08:30 PM.