Basic Considerations for Welding ASTM A514/A514M Steel
Cost and efficiency are two factors that dictate manufacturing and fabricating trends across most industries. In addition to implementing lean workflow practices —better, faster transportation and processing, and less wasteful inventory—many companies turn to the use of higher strength, lighter weight materials to reduce costs and improve productivity during welding.
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ASTM A514/A514M-05 high strength, low alloy Q &T steel is among those materials and has been for many years. Still, it poses some distinct challenges for welders.
This article discusses some key factors to consider when welding A514/A514M-05, including preheating and interpass heat requirements and precautions, and filler metal choices.
The What’s and Why’s
A514/A514M-05 is a specification for 100ksi yield low alloy quench and tempered steel intended for structural applications and is typically known in the industry as USS (United States Steel) nomenclature T1®, regardless of the manufacturer.
There are several grades of A514/A514M-05: Grades A, B, E, F, H, P, Q, and S. Each grade has a different chemistry requirement and may differ in the maximum thickness to which it may be rolled, ranging from 1 ¼ to 6 inches.
The mechanical property requirements of this type of steel are affected by the material thickness. The mechanical properties of A514/A514M-05 rolled to 2 ½-inches thick or less are as follows: 110ksi to 130ksi tensile strength; 100ksi minimum yield strength; and 18% elongation.
For materials 2 ½- to 6-inches thick, the mechanical properties are: 100ksi to 130ksi tensile strength; 90ksi minimum yield strength; and 16% elongation.
Hardness for material thickness up to and including ¾ inch are 235 to 293 HBW (Brinell). Note: there are no hardness requirements for materials that are greater than ¾- inches thick.
One of the reasons for the difference in properties between these thicknesses is the quenching of the material. The thicker the material, the slower the quench rate, which may result in lower minimum yield and tensile strengths as indicated by the material specification.
Typically this material is used for structural applications. In many cases, the term ‘structural’ refers to buildings, but the material is also used in heavy equipment structures to reduce weight and improve payload capacity, such as in rail cars and their components, large mining truck frames, semi-trailer frames and crane boom sections.
Due to the typical hardness of 22 to 27 Rockwell C of the material, it is also used for wear strips, cutting edges and side cutters, particularly on backhoe buckets and other earthmoving equipment wear applications.
Making the Choice: Filler Metals
Welding A514/A514M-05 is not complicated when some precautions, especially with filler metal choices, are used. Filler metals that deposit weld metal with diffusible hydrogen content greater than 8ml/100 grams of deposited weld metal should not be used on this material. It is sensitive to diffusible hydrogen, which may result in hydrogen cracking. The filler metal strength depends on the application of the A514/A514M-05 to be welded. Figure 1 shows filler metals to match the strength of base material thicknesses of 2 ½ inches or less where the same mechanical properties as the base material are required:
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On base material thicknesses greater than 2 ½ inches, the material may be welded with the same filler metals as for the thinner material in the previous example, but it will provide overmatching strength.In Figure 2 are the filler metals used for matching strength for material greater than 2 ½ inches:
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When A514/A514M-05 material is joined to other low alloy steels or carbon steels of lower strength, the filler metal strength requirements need only meet the lower strength base material properties. For example, when welding ASTM A36/A36M to A514/A514M-05, the application would typically require a 70ksi tensile strength electrode to match the lower strength material. Here, precautions should still be taken to minimize diffusible hydrogen that could lead to cracking.
Heat Input Control
Even though A514/A514M-05 is readily weldable, its mechanical and chemical properties can be undesirably altered by excessive preheat and interpass temperatures, and heat input. For that reason, precautions should be taken.
Typical preheat and interpass temperatures for A514/A514M-05 are found in Figure 3. These temperatures apply whether welding A514/A514M-05 to itself or to other lower strength materials.
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It should be noted that preheat and interpass temperatures above those shown in Figure 3 may alter the mechanical properties of the material. The use of Tempil® Sticks, contact pyrometers, infrared thermometers or other heat measuring devices should be used to control preheat and interpass temperatures. In addition to the preheat and interpass temperature controls, heat input, which is a function and calculation of amperage, voltage, and travel speed, must be restricted. Heat input is expressed in joules/inch and the calculation formula is as follows:
Travel Speed (inches/minute)
Typical heat input is around 55,000 joules per inch (+/- 20%). For other heat inputs, it is advisable to contact the steel manufacturer for other recommendations.
As a final precaution, A514/A514M-05 is not intended to be used in the Post Weld Heat Treated (PWHT) condition, as it will alter the mechanical properties for which the material was intended.
Other sources of information for welding A514/A514M-05 low alloy quench and tempered steel may be found in steel manufacturer’s fabrication guides; the AWS D1.1, “Structural Code—Steel”; D14.3, “Specification for Welding Earthmoving, Construction, and Agricultural Equipment”; D15.1, “Railroad Welding Specification—Cars and Locomotives”