Written by Ed Craig.
www.weldreality.com.





ASTM - A645 - A973 Steels

ALL ELECTRODE RECOMMENDATIONS MADE AT THIS SITE
REQUIRE CONFIRMATION AND QUALIFICATION.


Note: When you see high tensile weld electrodes required, this is usually an indication that pre heat interpass and post heat treatment is required for the welds.

 

 

What is fatigue?The ability of a metal or weld to withstand repeated loads. Fatigue failures occur at stress levels less than the metal or weld yield strength. Some things that can influence fatigue failure:

• Excess and irregular weld profiles.
• Weld undercut.
• FCAW or SMAW slag inclusions or excess / oversize porosity.
• Lack of weld penetration.
• Excess weld heat, typically from multi-pass welds without inter-pass temp controls.
• Parts that add restraint while welding.
• Items added to a part that can concentrate stresses in a specific location.
• Incorrect selection of filler metal, welds too weak or weld too strong.
  
  

When welding low and medium carbon steels, the 70XX electrodes and E70S-3-6 MIG wires and E7XT-X flux cored electrodes can be used. When welding low alloy 1 1/4 Cr 1/2 Mo and 2 1/4 Cr 1 Mo with up to 0.05% max carbon, typically 8018-B2L / 9018-B3L (L = low carbon) can be used. When welding higher strength alloys or when tempering and quenching are required to attain the higher strengths the higher carbon 8018 B2 and 9018 B3 electrodes are utilized. Best weld properties with lowest weld heat attained with TiP TiG, vist www.tiptigusa.com..

SMAW and GMAW Mechanical Strength
E6010 Minimum Yield 50,000 psi Minimum Tensile 62,000 psi.
E6011 Minimum Yield 50,000 psi Minimum Tensile 62,000 psi.
E7010 Minimum Yield 60,000 psi Minimum Tensile 72,000 psi.
E7018 Minimum Yield 60,000 psi Minimum Tensile 72,000 psi.

MIG E70S-3-6 Minimum Yield 60,000 psi Minimum Tensile 72,000 psi.

Mechanical Strength of Gas Shielded Flux Cored Electrodes from
ANSI/AWS A5.29. 1198 Specifications

Low Alloy Steel Electrodes for Flux Cored Arc Welding.

What is Brittleness? The ease at which the weld or metal will break or crack without appreciable deformation. When a metal gets harder it becomes more brittle. Preheat, inter-pass temp controls and post heat all are designed to reduce the potential for brittleness.

What is Lamellar Tearing? When welding, the weld shrinkage stresses impose tensile strains in the steel plate or on inclusions paralleled to the plate surface. The tensile strains can separate the inclusions causing cracks. Excessive strains can further elongate the cracks. Carbon, manganese and low alloy steels made at the mill with inadequate deoxidization are sensitive to lamellar tearing. The potential for lamellar tearing increases with the amount of inclusions in the plates being welded. Of special concern is when the inclusions are parallel to the plate surface. More data in ASTM A770 / A770M Standard Spec for through thickness tension testing of steel plates.

 

Welding alloy steels often may require unique weld or heat treat considerations. Compare the low alloy steels chemistry and mechanicals with a standard A36 steel. Remember this site is only a guide, weld responsibility starts with "you" First verify the weld consumable and then the material heat treat recommendations.

What is yield strength?. The yield is the he stress that can be applied to a base metal or weld without permanent deformation of the metal.

What is the tensile strength? The ultimate tensile strength" is the maximum tensile strength that the metal or weld can with stand before failure occurs.

Metric Conversion 1000 psi = ksi x 6.894 = MPa

STRESS RELIEVING (SR) BASIC GUIDELINES:

• STRESS RELIEF - CONTROLLED HEATING & COOLING TO REDUCE STRESS.
• STRESS RELIEF MACHINED PARTS FOR DIMENSIONAL STABILITY.
• STRESS RELIEF SLOW HEATING AND COOLING REQUIRED
• CONFIRM WITH CODE SPECIFICAIONS FOR STRESS RELIEF REQUIREMENTS.
  
  
  
  
  

When mill scale is a problem, what MIG or flux cored weld parameter needs to be changed and why? The mill scale weld solutions are in Ed's books.

What is Hardness? The resistance of the metal or the weld to penetration will determine the hardness. Hardness is also related to the strength of the metal. A good way to test the influence of weld heat on the part, is to test the hardness of weld and the base metal surrounding the weld.

 

 

What is Ductility? The amount that a metal or weld will deform without breaking. Measured on welds by the % of elongation in a 2 inch 51 mm test piece. An E71T-1 flux cored electrode should result in a minimum of 20% elongation. An E70S--6 MIG weld should produce approx 22%.

 

What is Toughness? The ability of the metal or weld sample at a predetermined temperature to withstand a shock. The test for toughness measures the impact of a pendulum on a notched specimen. You may see that the required impact properties for the metal or weld are 20ft-lbf @ -20 F (27 j @ -29C)

 

 

If you are welding a carbon steel and you don't know what the composition is or what the weld consumable should be, try the following:

• If the metal is thicker than 1/4 > 6 mm preheat to 150F.
• Use either an E7018 stick electrode, an 0.035 or 0.045 E70S-3- 6 MIG wire.
• For your all position welds an 0.045 E71T-1 electrode wire.
• For MIG welding use an argon 10 to 20% CO2 mix.
• For flux cored use a mix with 20 to 25% CO2.
• Ensure with multi-pass welds you use inter-pass temp control.
• Ensure the inter-pass temp weld temperature does not exceed 350F.
• If possible do destructive test of a weld sample.
• If possible have the hardness and grain size checked after welding.

Take note: When you see high tensile weld electrodes required, this is usually an indication that heat treatment is required for the welds