Materials used in mining equipment

Mining equipment makes use of a wide range of materials, from carbon steel, to manganese and austenitic stainless steel. In this article I will try to help new mining equipment operators understand what and when to use them as well as tips on welding.

Austenitic stainless steel

300 series stainless steels are classified as austenitic. They are hardenable only by cold working methods. These grades have chromium 18 up to 30% and nickel 6 up to 20% among other alloying additions, like manganese. Type 304 is the most widely used alloy of all stainless steels. 300 series stainless steel alloys resist corrosion, maintain their strength at high temperatures and are easy to weld.

Welding 300 series stainless steel

For stainless steel types 301, 302, 304L, 321, CF-3, and CF-8, use E308 electrode.

For stainless steel types 304, 304L, 309, 309L (often used in welding stainless steel to carbon, low-alloy, heat-resistant and clad steels), use E309 electrode.

For joining 316, 316L, CF-3 and CF-8 stainless steels; molybdenum is added to help prevent pitting and increase creep resistance use E316 electrode.

Depending on the application and/or thickness, flux-core electrodes may be better suited for welding 300 grade stainless steel. I’ve had a great experience using BLUESHIELD 652P-316L Stainless Steel Flux-Cored Wire (FCAW) in 0.045" diameter. It’s as easy to weld as E71T-1 and the slag peels off easy. Obviously, solid wire and stick wires can be used as well, with the disadvantages mentioned in a previous blog (see part 1 - "Stick or no stick").

Manganese steel

Manganese steel, sometimes called Hadfield steel, is a grade of low alloy steel used in high impact applications, like mining equipment hammers, crushers and jaws. Many people wrongly assume abrasive resistant steel like Hardox^® or other grades can be used to replace it. A client of mine used to replace the jaws on his excavator jaws crusher accessory with abrasive resistant material. After a lengthy talk, he agreed to allow me to build-up the teeth using manganese steel electrodes; suffice it to say, my client only needed another built 2 years later; think of the money savings and the low equipment downturn. Manganese steel is self hardening, that make machining and even grinding difficult. Although oxyacetylene can be used for cutting in the field, the preferred method is plasma cutting. Shops can also use water-jet cutting and laser.

Welding manganese steel

Welding manganese steel require special grade wire or sticks. A wire I have used for years and one that I’ve had great success with is Hobart TubeAlloy^® AP-O. It’s hard to source these days, but this wire can be successfully used in the field using a somewhat more powerful welding machine that can use 1/16" wire. This wire can be used to build-up manganese steel, join carbon steel to manganese steel, or weld manganese steel parts. Use a respirator, as this wire has a high content of manganese and chromium. As with most hard-facing overlay, this wire can be used in horizontal and flat positions only. Keep the inter-pass temperature low and you should be fine (manganese steel becomes brittle if allowed to heat-up too much).

Abrasive resistant steel

Abrasive resistant steel or AR, not to be confused with manganese steel, is a low alloy steel. The common AR grades are 400 and 450. These grades are relatively easy to weld following some basic rules. First, the choice of electrodes. Below is the electrode classification as recommended by SSAB in their Welding Handbook (copies are available for download on their website). Although recommended, I have never had an instance in which I had to use flux-core higher strength E8XT-X for any weld repairs or for manufacturing new equipment.

Second, control the heat input and the inter-pass temperatures. For single plate Hardox^® 400 20mm and Hardox^® 450 25mm, the material temperature should be at 20°C. Preheat as necessary.

Always weld stringer beads, never weave beads regardless of the welding technique.

In a future article I will talk about steel grades and what electrodes to use depending on the application and material. If you have questions or suggestions regarding future articles, you can contact the author by clicking on the name below.

This email address is being protected from spambots. You need JavaScript enabled to view it.