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Wednesday, December 10, 2008

Welding ASTM A514 or A514M-05 steel?-Before you do, take a close look at filler metals, heat input

The FABRICATOR®

Welding ASTM A514 or A514M-05 steel?

Before you do, take a close look at filler metals, heat input

By Dean C. Phillips, Contributing Writer
June 12, 2007

As manufacturers strive for lower costs and greater efficiencies, they tend to substitute high-strength materials for standard materials. One such high-strength material is ASTM A514/514M-05. Although it is not difficult to weld, joining it successfully requires paying close attention to the preheat temperature, interpass temperature, and filler metal.

Welder image

Cost and efficiency dictate manufacturing and fabricating trends in most industries. In addition to implementing lean work flow practices—better, faster transportation and processing and minimal inventory—many companies turn to the use of higher-strength, lighter-weight materials to reduce costs and improve welding productivity.

ASTM A514 and A514M-05 high-strength, low-alloy, quenched-and-tempered steels are among these materials. Although they have been available for many years, they continue to pose some distinct challenges for welders. Welding these materials successfully is a matter of understanding some key factors, including filler metal choices and preheating and interpass heat requirements.

What It Is, Why It Is

ASTM A514 is a specification for 100 kilopounds-per-square-inch-yield, low-alloy, quenched-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.

A514 grades are A, B, E, F, H, P, Q, and S. Each grade has a unique chemistry and may differ in the maximum thickness to which it is rolled, from 1-1⁄4 in. to 6 in. The material thickness affects the mechanical properties. For instance, A514 rolled to 21⁄2 in. or less must have 110-KSI to 130-KSI tensile strength, 100-KSI minimum yield strength, and 18 percent elongation. For materials 21⁄2 to 6 in. thick, the mechanical properties are 100-KSI to 130-KSI tensile strength, 90-KSI minimum yield strength, and 16 percent elongation.

The hardness for material thickness up to and including 3⁄4 in. is 235 to 293 HBW (Brinell). Note that the specification does not list hardness requirements for materials thicker than 3⁄4 in.

One of the reasons for the difference in properties among these thicknesses is the quenching. The thicker the material, the slower the quench rate, which results in lower minimum yield and tensile strengths.

Typically, this material is used for structural applications. In many cases, the term structural refers to buildings, but the material also is used in heavy equipment structures to reduce weight and improve payload capacity, such as in railcars and their components, large mining truck frames, semitrailer frames, and crane boom sections.

Because the typical hardness of the materials is 22 to 27 Rockwell C, it is also used for wear strips, cutting edges, and side cutters. Typical applications are backhoe buckets and other wear components in earthmoving equipment.

Making the Choice: Filler Metals

Welding A514 is not complicated when some precautions, especially with filler metal choices, are used.

A primary concern is filler metal hydrogen content. You should not use filler metals that deposit weld metal with diffusible hydrogen content greater than 8 ml per 100 grams of deposited weld metal. A514 is sensitive to diffusible hydrogen, which may result in hydrogen cracking.

Filler Metal Selection
ASTM A514 and A514M-05 up to 21/2 Inches Thick

Welding Process

AWS A5 Specification

Classification

SMAW

A5.5/A5.5M-2005

E11018M or E12018M

GMAW

A5.28/A5.28M-2005

Solid electrodes ER 110S-1 and
ER120S-1 or
Metal-cored electrodes E110C-K3,
E110C-K4, and E120C-K4

FCAW

A5.29/A5.29M-2005

E11XT1-K3C and -K3M
E11XT5-K3C and -K3M
E11XT5-K4C and -K4M
E12XT5-K4C and -K4M

SAW

A5.23/A5.23M-1997

Solid electrode/flux combination
F11AX-EXXX-XXX and F12AX-EXXX-XXX
or Composite electrode/flux
combination F11AX-ECXXX-XXX and
F12AX-ECXXX-XXX

Figure 1

The filler metal strength depends on the application of the A514. Figure 1 shows filler metals you can use to match the strength of base materials up to 21⁄2 in. thick where the same mechanical properties as the base material are required. On base material thicknesses greater than 21⁄2 in., you can use the same filler metals, but their strength exceeds that of the base metal, a condition called overmatching strength (see Figure 2).

Filler Metal Selection
ASTM A514 and A514M-05 Greater Than 21/2 Inches Thick

Welding Process

AWS A5 Specification

Classification

SMAW

A5.5/A5.5M-2005

E10018M

GMAW

A5.28/A5.28M-2005

Solid electrodes ER 100S-1 or
Metal-cored electrodes E100C-K3

FCAW

A5.29/A5.29M-2005

FCAW A5.29/A5.29M-2005 E10XT1-K3C and -K3M
E10XT5-K3C and -K3M
E10XT1-K7C and -K7M
E10XT1-K9C and -K9M

SAW

A5.23/A5.23M-1997

Solid electrode/flux combination
F10AX-EXXX-XXX or Composite
electrode/flux combination
F10AX-ECXXX-XXX

Figure 2

When joining A514 to other low-alloy steels or carbon steels of lower strength, use a filler metal with strength that meets the lower-strength base material's properties. For example, when welding ASTM A36 to A514, use a 70-KSI-tensile-strength electrode to match the lower-strength material. Don't focus solely on strength; keep the hydrogen cracking risk in mind.

Heat Input Control

Even though A514 is readily weldable, excessive preheat and interpass temperatures and welding heat input can affect the alloy's chemical properties. Figure 3 lists typical preheat and interpass temperatures for A514. These temperatures apply whether you are welding A514 to itself or to other, lower-strength materials.

Thickness (In.)

Maximum Preheat and
Interpass Temperature (F)

Maximum Preheat and
Interpass Temperature (F)

Up to 3⁄4

50

400

3⁄4 – 11⁄2

125

11⁄2 – 21⁄2

175

400

More than 21⁄2

225

Figure 3
Although welding A514 is not difficult, joining it successfully requires close attention to the preheat and interpass temperatures.

 

It should be noted that preheat and interpass temperatures higher than those shown in Figure 3 may alter the mechanical properties of the material. 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 of amperage, voltage, and travel speed, must be restricted. Heat input is expressed in joules per inch. The formula is:

Heat Input (joules/in.) = (Amperage ¥ Voltage ¥ 60) ÷ Travel Speed (IPM)

Typical heat input is about 55,000 joules per in. (±20 percent). For other heat inputs, it is advisable to contact the steel manufacturer for recommendations.

As a final precaution, A514 is not intended to be used in the postweld 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 steel are the steel manufacturers' fabrication guides and:

·  AWS D1.1, Structural Code—Steel

·  D14.3, Specification for Welding

·  Earthmoving, Construction, and

·  Agricultural Equipment

·  D15.1, Railroad Welding Specification— Cars and Locomotives.

Want more information?

Visit www.thefabricator.com; enter the article number (digits only) in the home page search box:

·  "Cracking the case" 1397

·  "MIG—welding tips and resources" 1083

·  "Preventing welding-related fires" 952

 

 

 

 

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