Never Use Manganese In Abrasion Areas
Manganese is one of the most misunderstood steels for wear resistant steel applications.
Manganese is used extensively in the mining, aggregate, foundries, metal recycling, and railroad industries.
They all utilize Manganese in similar types of machinery, for the same functions in crushing applications. Whether you are shredding junk and car bodies or smashing large rocks into smaller sized rocks for specific applications; much of the equipment uses Manganese to combat wear.
Manganese Steel Advantages
Manganese steel stands up to constant impact longer than any other known material. Once work hardened, it will significantly resist impact longer than high carbon steel or cast iron, and will develop some abrasive wear resistance.
The key to Manganese steel effectiveness is beneath the work hardened layer, the core remains strong and ductile. When Manganese is exposed to impact, high stress scraping, gouging or pounding; Manganese can last up to 10 times longer than mild steel.
Naturally it will wear, but as the work hardened surface is worn away; the exposed metal beneath now becomes work hardened from the continual impact.
Do Not Use Manganese For Abrasion Applications
Abrasion from sand or other fine materials with little impact, rapidly wears the surface. Abrasion resistance of Manganese steel as cast, is no greater than mild steel. It is also less abrasive resistant than heat treated high carbon steel.
A perfect example of when not to Manganese steel was after a change in a hammer style coal crusher, feeding a coal fired boiler. Their equipment and process was designed to use Eastern Coal, which is very hard. Manganese is perfect for smashing hard materials, where the swing hammers and screen each work harden the surface under the constant impact. In that application, their hammers would last 6 months before changing.
The company decided they could reduce fuel costs by buying Powder River Basin Coal (PRB) from Wyoming, rather than the Eastern Coal. However, they didn’t realize that PRB coal is very soft. The change to softer coal meant the Manganese swing hammers without impact, had no ability to work harden. You can imagine their surprise when the same hammers that were lasting 6 months with Eastern Coal, were totally worn out in 3 weeks using PRB coal.
Don’t Just Treat Symptoms.
Always Look For The Causes Of The Wear.
After initially thinking they received poor quality hammers, investigation into what happened revealed the change in coal was the cause of the dramatic difference in wear. For a period of time the customer had to build up and hardface the worn hammers, as shown in the first photograph.
By then switching to an alloy steel hammer with a higher Rockwell hardness instead of the Manganese steel; their hammer life again returned to 6 months before replacement was needed.
Manganese Steel Properties
The most popular type of Manganese is known as Hadfield Manganese, invented by Sir Robert Hadfield in 1882. Hadfield Manganese steel typically has a direct 10 to 1 ratio of Manganese to Carbon. The standard range for Hadfield Manganese contains 11% to 14% Manganese, with 1.1% to 1.4% Carbon. This ratio is critical for increasing the strength and hardness in Manganese steels.
As cast, Manganese is relatively soft, registering 187 BHN or only 10 Rc.
Impact By Repeated Hammering Increases The Hardness And Strength Of The Manganese Castings
Surface hardness from impact can reach a maximum of 550 BHN or 55 Rc. The depth of the hardness will depend on the richness of Manganese steel chemistry, and the frequency and pressure of the applied impact stresses. The lower the percentage of Manganese and Carbon, the lower the hardness scores you will achieve.
Yield strength of Manganese steel is about 66,000 PSI and ultimate tensile strength is about 107,000 PSI. Elongation is 35% in 2 inches.
Identification of Manganese Steel
In the field Manganese is identified with a magnet. As produced, Manganese is not magnetic or attracted by a magnet. After being used for a period of time, the impact wear areas will have a slight magnetic pull.
The non-impact areas, the sides or back of the casting remain non-magnetic. It is the work hardening that makes the impacted surface slightly magnetic. This is the only metal known to have this magnetic change.
Heat Effects on Manganese Steel
Manganese is usually found as a casting; or formed into bar stock, plate or angle shapes. Manganese steel is expensive to machine, which is why most parts are cast to shape and finished by grinding. As cast, Manganese steel that has not been heat-treated, is very brittle because of the Manganese carbides.
Standard toughening treatment at the foundries, consists of slowly heating the steel to 1850° and quenching it in water. This heat treatment gives Manganese steel it’s high strength and toughness.
NOTE: If any later fabrication process raises the temperature above 500°F, this toughening treatment MUST be repeated.
Where alloy steels gain strength from heat treating, Manganese steel loses ductility when exposed to high temperatures. Most people don’t know it can become brittle and prone to cracking in application when overheated.
Sustained Temperatures Of 500°F To 800°F May Cause Manganese To Become Brittle
SO, WHAT SHOULD YOU USE INSTEAD FOR YOUR ABRASION WITH IMPACT APPLICATIONS?
Our QT-PLUS® proprietary chemistry and unique heat-treating process produces a premium quality severe impact and abrasion resistant plate unmatched in the industry.
This incredibly tough and hard steel with extraordinary ductility, is produced with tightly controlled carbon levels for ease of weldability, and excellent formability.
QT-PLUS ® is alloy rich and is a “true” through-hardened plate so it retains the same hardness throughout the entire plate thickness. By comparison, the low alloy content in commodity-grade steels, doesn’t allow for through-hardness of the plate, resulting in rapid wear.
For over the last 44 years, JADCO has focused exclusively on delivering consistent, longer equipment life for our customers.
Now you understand why we are able to deliver better results to our customers. We think differently by strictly focusing to improve your current results.
Allow us to help you today by emailing us at info@jadcomfg.com or calling (724) 452-5252.
We will schedule a meeting with one of our local wear plate specialists at a time that best fits your schedule.
Remember, the only thing you have to lose by not working with JADCO, are your profits
