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ESAB Knowledge center.

Choosing the Right Filler Metal for A513 HSLA 70 Steel

Q: We have a job coming up involving hand rails, stairs, and tables for outdoor use. The engineers chose A513 HSLA 70 steel because it is thin and saves on weight. In the past we used A500 and welded it with an E70 filler metal. Because we are now using a material that is thinner and higher in strength, should the filler metal we use match the base material or can we continue using E70?

A: It appears there is some information missing in your base material description, but here are some guidelines that will help answer your question. Let's start with the basic differences between ASTM A500 and ASTM A513 steel.

ASTM A500 and ASTM A513 are specifications of steel and both has multiple grades. ASTM A500 is manufactured from cold-formed welded seamless carbon steel and ASTM A513 is manufactured from electric resistance welded carbon and alloy steel. Both steels are of the tube type, such as rounds, squares, and rectangles. In addition, there are several ways these steels are manufactured.

A500-type steels are found in load-bearing applications like structural steel, including building columns, communication towers, and road signs. You'll also find it in architectural works where the architect wants to showcase the structure out in the open. The applications and uses of this material mean it will have minimum and sometimes maximum strength requirements.

A513 is more commonly used in consumer products such as metal furniture, recreational vehicles, lawn equipment, and exercise equipment. It is manufactured with tighter dimensional tolerances but is not considered load-bearing, so it is not required to have a minimum strength requirements.

ASTM A513 HSLA 70 could be from one of several different grades. It is possible it is a weathering grade, which requires some low alloy such as 1 percent nickel to control the rusting of nontreated surfaces. The low amount of alloy would likely boost the mechanical properties, giving it a higher strength classification. If that is the case, then matching it with a weathering grade type filler metal such as a 1 percent nickel would provide good color match while in-service.

If the engineers chose this grade for higher strength, they would have special-ordered it that way. There are two main reasons that they would have done this:

  1. To reduce weight and maintain integrity or stability of the welded assembly as you mentioned.
  2. To increase the strength or expected loads applied to the welded assembly.

If No. 1 is the reason, then you wouldn't necessarily have to match the base material strength with an expensive alloy filler metal. With the engineer's approval, you could weld the items with an E70 classification filler metal.

If No. 2 is the reason, then welding with an equivalent-strength filler metal is necessary. For that you would need to verify base material mechanical properties to match a filler metal, which could be anywhere from an E70 up to an E110 classification.

In many cases for this type of application, A513 or a higher grade is used for weathering properties or to reduce weight while maintaining the product's rigidity. If strength is desired, then typically a base material such as an ASTM A519 is used, for example. 

 

This article originally appeared in The WELDER magazine.
It is reprinted here with permission of the Fabricators & Manufacturers Association, Intl.

Posted in Filler Metals , Tagged with Steel

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