ASTM - A403-A643 Carbon Low Alloy Steels,


Bar,Plate and Pipe

ALL ELECTRODE RECOMMENDATIONS MADE AT THIS SITE REQUIRE WELD QUALIFICATION BEFORE THE WELD CONSUMABLES ARE APPROVED.
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

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 weld profiles.
• Welds which cause undercut.
• FCAW or SMAW slag inclusions.
• Lack of weld penetration.
• Excess weld heat, typically from multi-pass welds without inter-pass temp controls.
• Items to a part that adds restraint while welding.
• Items added to a part that can concentrate stresses in a specific location.
• Incorrect selection of filler metal, weld 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.

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 the ANSI/AWS A5.29.
1198 Specification Low Alloy Steel Electrodes for Flux Cored Arc Welding

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.

 

 

Hardness test. The hardness tester forces a small sphere (Brinell, HB), a diamond pyramid (Vickers, HV) or a cone (Rockwell C, HRC) into the surface of a metallic material. The indentation is then measured.

 

Many manufactures of parts and equipment containing ASTM steels do not use the recommended pre or post-heat treatments. The requirements for weld heat treatment is greatly influenced by many factors, the application, the governing specifications or codes, the plate condition, plate thickness, the weld consumables the weld procedures, the weld size and amount of welds required. In many cases the manufacturer that uses ASTM steels will find that it's not necessary for the weld to match the mechanical properties of the steel, (its often better for the weld to have more ductility than the plate) and therefore low hydrogen, highly ductile SMAW E7018 / E70S-3-6 MIG wires or E7XT-X flux cored electrodes are used. When using the low hydrogen electrodes, the pre and post heat treatment recommendations are frequently eliminated, however from a weld quality perspective always ensure that the weld locations are dry, the base metal is over 60 F, and that rust and mill scale is removed from the weld area. Also even when heat treatment is not used its frequently beneficial to not allow the multi-pass inter-pass weld temperatures to exceed 250 F. If you ignore the heat treat requirements as recommended by the metal specifications ensure you use low hydrogen electrodes then, (a) Establish the weld procedure. (b) Qualify the weld and HAZ properties. (c) Ensure the after weld and HAZ properties are compatible with the steel specifications, ref grain size, hardness and strength. PRE HEAT PROVIDED IN THESE CHARTS ALSO APPLIES TO MINIMUM INTER-PASS TEMPERATURE

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.

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

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

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.

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

 

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.
  
  
  

 

E-Mail Feb2007What affect does flame cutting API X-80 or 550 gr. pipe have on the HAZ? Is 6010 a good root pass rod for this material?

From Brian : It may be that all X-80 is not creaed equal: it could be seamless quench and tempered, or DSAW TMCP plate. We have had some seamless that had a high alloy content, with a very hard HAZ, and could be susceptable to hydrogen cracking - need to consider minimum preheat and would personally try to avoid any cellulosic rod such as that 6010, but that is just my own bias. The TMCP material we have used was marvelous - soft HAZ, low minimum preheat..wonderful in every way except price tag!

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Hardness:
The resistance of the metal or the weld to penetration. Hardness is related to the strength of the metal. A good way to test a weld after the weld and heat treatment are complete, is to test the hardness of weld and the base metal surrounding the weld.

 

 

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%.

 

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 6 mm preheat to 150F.
• Use either an E7018 stick electrode, an 0.035 or 0.045 E70S-6 MIG wire. For your all position welds an E71T-1 electrode wire.
• For MIG welding use an argon 10 to 15% 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 200F.
• If possible do destructive test of a weld sample.
• If possible have the hardness and grain size checked after welding.
  
  
  
  

Name two reasons why inter-pass temperature control is essential
for some multi-pass welds.

[1] Inter-pass temperature control can restrict the weld and base metal grain g____h

[2] Inter-pass temp control can limit the weld h___t

Name two reasons why pre-heat is essential for some steels.


[1] Preheat can remove sources of h______ n

[2] Preheat can slow down the c______g rate.