ASTM - A3 to A391 Carbon Low Alloy Steels.


Bar, Plate, Chain Tubes 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.

IF YOU ARE WELDING TUBES OR PIPES MAKE SURE YOU VISIT THE
ASTM PIPE SECTION

If welding a carbon or low alloy steels and you don't know what the composition is or what the weld consumable should be, give consideration to 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, or for all position welds an E71T-1 electrode wire.
• For MIG welding use an argon 10 to 15% CO2 mix.
• For gas shielded flux cored use a gas mix with 20 to 25% CO2.
• Ensure mill scale in weld area is removed and the plate is dry and at a temperature >60F.
• Keep single pass fillet welds < 6mm.
• Do not weave unless necessary.
• For multi-pass welds use inter-pass temp control. Ensure the inter-pass temp does not exceed 250 F.
• If possible do destructive test of a weld sample.
• If possible have the hardness and grain size checked after welding.
• If cracks occur in the HAZ double the pre-heat.

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.

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.


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.

Fine-grained steels are prone to cold cracking due to hydrogen absorption. They should be preheated slightly and welded with a relatively low specific energy, to reduce the heat-affected zone. Preheating: in function of steel, generally 100°C (max. 200°C) Post-weld treatment: usually not necessary

Austenitic manganese steels with a manganese content of 14% (Hadfield steels) have a tendency to form brittle precipitates in the form of carbides.
It is essential to weld them without preheating, even with additional cooling, and to keep the specific heat input low. Preheating: none (cooling may be used if needed

Unalloyed steels are prone to cold cracking. In many cases preheating is required to ensure good weldability. Preheating: < 0.2C %: without preheating (up to 30 mm thickness) or 100°C against humidity

C: 0.2 to 0.5 %:preheating temperature 100 to 300°C

C > 0.5 %: preheating temperature 300 to 350°C.Possible post-weld treatments, stress relieving, normalising

Low alloy steels are prone to cold cracking. In many cases preheating is required to lower hydrogen potential and ensure good weldability.

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. The ease at which the weld or metal will break or crack without appreciable deformation. 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 at a specific load. The resulting indentation is then measured.

 

 

Alloy steels always require weld consideration. Compare the low alloy steels chemistry and mechanicals with a standard A36 steel. Remember this is only a guide, weld responsibility starts with the weld decision maker verifying the consumables and heat treat and test recommendations.

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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.
  
  

Metric Conversion 1000 psi = ksi x 6.894 = MPa

Many steel types and their grades go back for 30 to 50 years. Today many grades are obsolete. Its helpful to include these grades as many rebuilds and repairs deal with the older grades. By the way if you don't see a chemistry range you are typically seeing the maximum alloy content.

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.
  
  

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.

Weld Question: When you see an electrode recommendation such as E8018-C1, who is the best reference source to convert that stick electrode to a flux cored or MIG wire?


Answer: I believe both Alloy rods and Tri Mark, flux cored manufacturers have good reference data for this subject.

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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)

Weld Question: Ed. Which should be the greater concern
rust or mill scale.


Answer: Mill scale causes much more weld issues than rust. Mill scale can effect
[1] the weld fusion potential,
[2] the weld travel rates attained,
[3] the weld appearance,
[4] the weld mode,
[5] the arc stability,
[6] weld spatter formation.

Ductility: The amount that a metal or weld will deform without breaking. Ductility is measured on welds by the % of elongation in 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 22% elongation.

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Weld Question: Ed. I have welded parts at Caterpillar plants. They weld many of the ASTM steels listed here. They rarely use pre-heat even on the very thick steels. Why do they not comply with the ASTM specs heat treat requirements?

Answer: "A spec is only a spec"

No code or specification body takes responsibility for what is written in their codes or specifications. Specifications are set of guidelines. In the case of the ASTM specs the heat treat recommendations are to make the weld properties conform with the base metal properties yet many times its not practical or logical to do this. If an organization produces multi-pass welds, the multi pass heat input act the same as a post heat treatment and the extra passes will have an extensive influence on the mechanical properties of the welds and the base metals.

Qualification of the multi-pass welds and HAZ with the specific weld procedures utilized always will have far more relevance than a specification which was typically written for a single pass weld.

 

Hardness. The resistance of the metal or the weld to penetration. 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.

Weld Question: What do you think the optimum wire feed and weld voltage range is for welding with an E70T-1 1/16 062 flux cored wire welding a 1/4 fillet weld. The answers are in my books.

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Ed in Thailand managing a Textron project.
The mission fix a 276,000 psi tensile steel
armor plate,mult-million dollar
welding problem:

This Textron, Detriot built tank was made out of 275.000 ksi tensile, armor steel. Due to lack of weld manufacturing quality at the Detroit facility some parts were welded in the wrong location between the tank tracks. These welded parts were subject to abnormal stresses that resulted in numerous cracks when the tanks were field tested in Thailand.

If you tried to repair the cracked welds which had extensive martensitic formation in their HAZ, more cracks would instantly occur from the weld repair heat input. What would you recommend to resolve this multi-million dollar issue. This was my first consulting job and it was a real welding challenge.