Alloys for Steels
Steel is probably the most important of all the base metals. It is the most commonly welded metal in maintenance applications. Most steels are welded easily without problems. However, some steels can cause problems when welded unless certain precautions are taken. The steels we will be discussing in this section will be the low alloy grades.Low alloy steel has less than 3% of alloying elements. The most common grade of low alloy steels is the AISI (American Iron Steel Institute) grade 1020. The Society of Automotive Engineers (SAE) uses a similar designation system. These two organizations dictate the specifications of all steels. Other types of low-alloy steels are as follows:
The higher the carbon content in a steel, the higher
the hardness will be after welding, unless certain preheating procedures
are used. When steels with high carbon contents are welded and cooled
rapidly, the weld deposit and heat affected zone will be very hard.
Depending on the location of the weld joint it is either restrained or
unrestrained. (See Figure 1 following page) If unrestrained, the weld
can contract as much as needed. If restrained, that is, still connected
to another area, the contraction will cause another crack to develop,
causing the weld area to literally pull away from the connected area. By
applying certain precautions, cracks in restrained joints can be avoided
and successful welds made. The key is to determine the carbon content of
the steel being welded. Remember, cracks will come from higher carbon
content steels cooling rapidly. If the steel has a low carbon content,
it will remain relatively soft or ductile. The shrinkage that will occur
wont create problems because of the ductility of the weld area. An easy
way to determine carbon content of the base metal is to use a torch to
heat an edge or corner to red heat, then quench in water. Using a hand
file, try to file the area that was heated and quenched. If it files
easily, the carbon content is low; if it is difficult to file, it has a
high enough carbon content to create problems. The more difficult it is
to file, the higher the carbon content. When medium and high carbon
steel are welded, pre and post-heat procedures can be used to help assure
crack-free deposits. Following is a table with the recommended preheat
for common grades of low alloy steels as well as some commonly used
types of trademark steels in this classification.
Easiest to use all position electrode for steels.
Very low amperage requirement on AC and DC.
Ideal for out of position welding.
Outstanding re-strike characteristics, minimal spatter, and self-releasing slag.
Great for fabrication of thin, medium, heavy, and dissimilar sizes and grades of steel.
For uses such as: sheets & plates, angle iron, pipes, build-up of worn surfaces, general construction and repair applications
|MG 500 W
Same characteristics as MG 500, but in a self-shielded flux cored wire.
|MG Tool Box
Includes a durable, reusable black MG Tool Box.
Tool Box filled with 20 lbs. of MG 500 1/8 diameter.
General purpose, all position electrode for dirty mild steel.
Special flux coating is ideal for vertical-down and overhead applications.
Deep penetration on rusty and scaly steel.
Very little spatter.
For uses such as: painted surfaces, structural steels, tack welding, and mild steel pipe.
High strength, all position electrode for extremely contaminated steels.
Low amperage requirement allows for poor fit-up applications and use on buzz boxes.
For uses such as: light gauge steels, steel beams & girders, pipeline welding, automobile repairs,
agricultural equipment, and tank fabrication.
|MG 506 W
Gas shielded, flux cored mild steel wire for dirty, rusty, or painted steels.
Single or multi-pass.
Flat and horizontal welds.
Widely used for general structural steels.
Uses such as shipbuilding steels, boiler plates, pipe steels, non-aging steels, high sulphur and Tramp Steels, steels with high carbon, phosphorus and/or sulphur content.
Meets AWS A5.1 E7018
Super high strength low hydrogen electrode.
For high tensile finely grained carbon steels.
Outstanding elongation and ductility.
Easily machined deposits.
For uses such as: earth moving equipment, cranes, heavy duty vehicle bodies, scaffolding, superstructures, and armor plates.
Controlled hydrogen electrode for problem steels.
All position, low amperage electrode with high deposition.
For difficult to weld steels high in sulphur, phosphorus, etc. Dense, crack-free deposits with good ductility.
For uses such as: H & I beam fabrications, circular tube to plate, channel iron, pipelines, and angle iron.
|MG 540 TIG
Same characteristics as the MG 540, but in a 36 cut length TIG wire.
|MG 540 W
Gas shielded, all position, flux-cored wire for mild and low alloy steels.
Excellent for steels high in sulfur, phosphorus, or unwanted tramp elements.
Use 75% AR 25% CO2 or 100% CO2 shielding gas.
Premium low alloy, high strength electrode.
Excellent low-temperature impact properties.
High deposition, all position usability and crack-free deposits.
For uses such as: mining equipment, paper industry equipment, and construction equipment.
AC or DC straight electrode designed for cutting, beveling, and piercing of all metals.
High speed chamfering electrode.
Performs well on AC and DC welding machines.
Excellent re-strike characteristics and dross removal.
Easy to control the size and depth of the groove.
Also suitable for cutting & hole-piercing.
For uses such as: carbon steel, stainless steel, cast iron, aluminum, copper & copper alloys, and cast steel.
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