Do You Know Which Wear Material You Are Currently Using?

Compare these spark testing photos to determine which metals you are using for you wear resistant  steel applications.

Many wear applications will use mild steel, high carbon steel, manganese, white cast iron, AR steel, alloy steels and chrome-carbide overlaid plates, or even some stainless steels. 

Many times people are unsure what they used the last time, can’t remember what they bought or who sold it to them.  It may be on used equipmen, or was installed before you started your current position.  Or lost forever in the last computer “upgrade”.

You can quickly and easily determine what material you are using by simply using a magnet and by lightly touching the steel with a hand held grinder.  Notice the following to identify which materials are which:

1. Length of Spark - the longer the spark, the lower the amount of carbon.
2. Color of Spark - the lighter the spark, the lower the amount of carbon
3. Spark volume - More alloy results in a larger spark volume.
4. Forks or Bursts - Indicate alloys present in the material.  Forks are where one spark splits into two or three. Bursts are where one spark splits off into many, as shown below. 
5. Repeating or Ending Forks or Bursts - Notice if the forks or bursts occur at the end of the spark or repeat along the spark stream.

Repeating Forks               Here are Repeating Bursts

With this information, you will be able to quickly determine what materials are currently installed.  Combining this with the recommended materials for specific applications in the following sections, and you will know which to select for the longest life for your use.

Performing the Spark Test:

Start with a known piece of mild steel for a comparison basis.  What you will see with mild steel are long, light-colored sparks with no forks and no bursts. 

Mild Steel - The sparks may travel over ten feet.  Having almost no forks or bursts means it contains no alloys. The low carbon content of 0.2% to 0.3% will yield light yellow sparks.   

 Mild steel will have an average hardness of 130 BHN, and used for structural purposes, and is not recommended for wear resistance.

Here is the spark test on a file for comparison - notice the large spark volume, short orange sparks with repeating bursts, which indicate high carbon steel with significant alloy content.

I heated this file red hot to anneal it.  It is no longer hard.

Here are the sparks from the annealed file showing the same sparks as the prior sample.  This is included is to show that sparks indicate alloys are present in the steel; It does not indicate hardness. 

 Plain Carbon Steel vs. Alloy Steel

Alloy steels have special physical and mechanical properties due to the presence of metal elements such as nickel, chromium, vanadium, tungsten or higher levels of silicon or manganese over that found in plain carbon steels.

To illustrate the difference between plain carbon and steels with additional alloys, the next two photos show steels with approximately the same carbon content. 

1045 is a plain carbon steel, with no alloy, containing 0.45% Carbon and .75% Manganese.  It has a low volume of yellow orange sparks traveling over 6’, and no forks or bursts.

4140 is an alloy steel containing 0.45% Carbon, and 0.85% Manganese, 0.25% Silicon, 1.00% Chromium and 0.20% Molybdenum.

4140 Steel has a greater spark volume with repeating forks and bursts, yellow to orange sparks, 8’ to 10’. 

Comparing the difference in spark volume, presence of forks and bursts, show there are additional alloys present in 4140 steel that are not in the 1045 steel.

Manganese – steel is non-magnetic as cast.   Magnetic only in impact areas, this makes it the only wear resistant steel you can identify using a magnet.  Manganese Steel has a large spark volume traveling over 6’, yellow orange sparks with no forks or bursts. 

The greatest attribute of manganese is the ability to work harden.  As the manganese work hardens, the impact area transforms to a slightly magnetic condition. 

Alloy Steel – Sparks are light yellow in color, up to 6’ long. 

Alloy steels have 4’to 6’ light yellow sparks in a medium spark stream where forks are common and bursts are possible, depending on the alloy content.  Notice how the above photo at .25% Carbon has a lighter spark color than either photo showing 1045 or 4140 steels which has .45 or .40% Carbon.

Chromium Carbide Overlay plate is easily identified by the irregular surface appearance, made by welding a mild steel base plate with a highly alloyed hardsurface welding wire. The surface on overlaid plates often show stress checks that are created in the manufacturing process. 

You can determine the quantity of chromium carbides present by comparing the number of stress checks present in the overlay. 

The greater the amount of stress checks, the greater the carbide content. 

Chromium carbide plate shows almost no sparks off the grinding wheel.  Just a thin red-orange spark stream ringing the grinding wheel.  This overlaid plate contains 46% Chromium-Carbide content, due to 36.7% Chromium, 4.8% Carbon, 1.6% Manganese, .67% silicon & iron balance,

 
Duracorr®, a product of ArcelorMittal Steel, is a magnetic, dual-phase stainless steel with 1% Carbon.  Sparks are light yellow, the larger spark stream with forks traveling 3’.  It contains Martensite & Ferrite for better abrasion resistance with 12% Chromium, 1% Nickel, .3% Moly.  Duracorr® has 0.25% carbon, 1.50% Manganese, 1.0% Nickel, 12% Chromium, .25% Moly & .70% Silicon.

Duracorr® is heat treated to 300BHN hardness with the corrosion resistance of the 300 series stainless steels.  It works well for wear applications having combined corrosion & abrasion issues.
 

White Cast Iron – is a wear resistant casting having over 30% Chromium and 5% Carbon.  They combine to form chromium-carbides like the overlaid plate.  Shown above, has very few reddish sparks less than 1’ long and few forks.

It is called white cast iron due to the silvery color when the casting is fractured.  It is cast to shape and is not weldable.

For comparison, Gray Cast Iron has no nickel or chromium and has slightly more spark volume.  It has few reddish sparks 1’ to 3’ long with a few forks and bursts.  It is called gray cast iron due to the color of the fracture, and is not used in wear resistant applications.

Perform magnet and grinder tests on known steels, then on your own “mystery metal” to determine what you have currently installed. 

Once you indentify what you are using, you are well on your way to determine which material is a better selection for your specific application.  

 



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