I'ANCO Alloy 2A (similar to 8630) has a combination of high strength and low temperature toughness. The combination of alloying elements produces a quenched structure consisting almost entirely of martensite. Upon tempering, this structure provides the best combination of strength and toughness. The presence of nickel adds to low temperature toughness.
Lower hardenability due to the absence of Cr, Ni and Mo make it more difficult to produce tempered martensite structure of equivalent hardness and toughness. The absence of nickel also reduces the low temperature toughness. Under extremely low ambient temperatures, this alloy may be more susceptible to failure.
I'ANCO Alloy 2A castings are quench and tempered for maximum toughness.
Typically bar stock is not supplied in QT form and must be heat treated if a quench and tempered product is desired. Other means of providing surface hardness do not create a uniformly hard and tough cross-section.
No welding is performed after the links are quenched and tempered. As a result, the entire link consists of metal of equal hardness and toughness. There are no residual stresses that act in an additive manner with external forces to produce a premature failure.
Cold forming of side bars results in residual stresses and strains that can contribute to premature failure.
Welding produces a complex structure consisting of base metal, weld metal and a heat affected zone. Thus, the link does not consist of homogeneous material of equal hardness and toughness. Without post weld heat treat, components can exhibit significant residual stresses.
The homogeneous nature of the cast link results in the entire cross section performing equally as a load bearing member, with equal toughness and strength at the surface.
Surface hardening can enhance the load bearing capability of a link and can increase its fatigue strength, provided that the combination of applied and residual stresses do not exceed the elastic limits of the link. In such cases the harder but less plastic surface layer can crack and accelerate failure.
Blended intersections of side bars with the link barrel reduces stress concentrations in critical areas.
Welded link-barrel junctions typically have higher stress concentration factors and have weld-related structural changes and potential weld defects in this critical area.
The larger cross-section of the cast link results in higher load bearing area, not only regarding tensile loading but also with respect to sliding wear.
Manganese Steel - Its History and Uses
Austenitic Manganese Steel was first discovered by Sir Robert Hadfield in 1882. Hadfield was working as a young man in his father's works in Sheffield, when his attention was called to some castings that had failed in service and which showed a hard and gritty fracture. The fault was found to be too high a silicon content. For some time he had been looking for metallic substitute for the then unsatisfactory emery wheel, and thought this might be the answer. He therefore experimented with steels containing high silicon and manganese.
It was from these experiments that he discovered Manganese Steel. While the attempt to make metallic grinding stones failed, it was found that an alloy containing some 10% manganese and 1% carbon was very hard, yet not too brittle to be of possible use. A lathe tool was cast of this alloy but it was found to wear out too quickly. Heating and quenching this new material produced unusual results. Instead of becoming harder and more brittle when quenched, if anything, it became softer and the elongation went to about 50%. It was this happy combination of analysis and treatment that gave us Austenitic Manganese Steel.
PROPERTIES
Manganese Steel as-cast is as brittle as cast iron. However, when it is reheated to about 1850 degrees F. and rapidly quenched, it has the greatest toughness of any steel and develops the following physical properties:
Tensile strength - - 100,000 to 130,000 lbs. per sq. inch
Yield point - - - - - - 30,3000 to 40,000 lbs. per sq. inch
Elongation - - - - - - - - - - - - - - - - 30% to 55% in 2 ins.
Reduction of area - - - - - - - - - - - - - - - - - - 30% to 45%
Brinell Hardness - - - - - - - - - - - - - - - - - - - 180 to 200
WORK HARDENING
While its "as treated" hardness is not much different from mild steel, continued impact increases the hardness tremendously, reaching a maximum of 550 Brinell, which is not far from the 600 Brinell of tool steels.
TOUGHNESS
Manganese Steel, while acquiring extreme surface hardness under repeated impact, still retains its 'as treated' toughness. This is due to the austenitic structure that is retained after the heating and quenching treatment, making the metal very strong and ductile and with a tensile strength of approximately 125,000 pounds per square inch. This combination justifies the reputation of Manganese Steel as being the toughest, yet hardest of all cast steels.
BENDING AND FORGING
Manganese steel should, where possible, be bent or straightened at ambient temperature. If heating is necessary, the casting should be re-heat treated and quench exactly the same as was performed in its original treatment.
WELDING AND HARD SURFACING
Manganese Steel can have worn parts built up or fractures welded by using nickel manganese or stainless steel rods. Where the action on Manganese Steel is mostly abrasive, wearing parts can be hard surfaced by using hard facing rods that have been developed for this purpose. In all cases, it is extremely important that welding or hard facing be done only by experienced manganese steel welders, as overheating will render the metal unsuitable for shock resistant applications.
PARTICULAR USES OF MANGANESE STEEL
Manganese Steel is the most suitable steel for crushers, shovel teeth, logging, cement production, dredging or any machine parts that are subject to both heavy impact and high stress abrasion. Under such conditions manganese steel provides a combination of toughness and wear resistance that is far superior to ordinary steels.
PRODUCTION TECHNIQUE
Unlike other alloy steels where an appreciable tolerance of casting details does not greatly impair the quality, production care in the manufacturing details of Manganese Steel is vitally important. While the Manganese content may safely vary from 12% to 14%, the relation of carbon, silicon, phosphorus, sulphur, homogenous mixing, refining, pouring temperature, heat treating temperatures for different sections, quenching temperature and timing, etc., must be strictly adhered to. Deviation from any one of these details could result in an inferior product and is the possible reason for some Manganese castings outlasting others, even though the chemical analysis might be the same.
I'ANCO MANGANESE STEEL is produced under the rigid supervision of the Metallurgical Department and all manufacturing details are strictly adhered to.
Log Haul & Waste Conveyors - Why I'ANCO Chain
The prime areas that concern a user of long link chain:
What style of chain and why
What materials and why
What manufacturing process and why
Style:
I'ANCO pioneered the use of the now increasingly popular, square profile cross section chain link. This design gives two distinct advantages:
The material cross section of the square profile is a minimum of 20% larger than that of the standard round profile, resulting in a substantial increase to the overall strength of the link.
As the critical part of a long link chain is the contact area between the links, when using round material the bearing area is in effect a point-to-point contact.
This means that the stresses involved must wear down this area until a sufficient cross section of bearing surface is achieved to carry the load of the conveyor, thereby reducing the life of the round profile link.
Square profile chain on the other hand, offers a much greater bearing surface and therefore the need to wear down the link in order to achieve full contact, is eliminated.
Material Selection:
Two common materials employed in cast steel long link are:
Austenitic Manganese Steel
Low Alloy Quench and Tempered Steel
I'ANCO has historically recommended and supplied most long link chain conveyors in Manganese steel, primarily because of its ability to endure severe impact. This, combined with its ability to generate a work-hardened surface in the range of 500-600 BHN, makes manganese an excellent choice for most long link applications.
That said, low alloy steel also has its place in the market. Although its ability to absorb severe impact is less than that of austenitic manganese, in the quenched and tempered condition the alloy steel offers higher ultimate and yield strength and greater abrasion resistance.
COMPARISON OF THE 2 MATERIALS
Manganese Steel 12-14% Mn
Low Alloy Steel
Ultimate Strength
110,000-130,000 PSI
130,000-150,000 PSI
Yield Strength
40,000-50,000 PSI
120,000-130,000 PSI
Elongation
30-50%
14-17%
Reduction of area
40-50%
20-40%
Hardness as manufactured
220-240 BHN
330-360 BHN
After work hardening
500-600 BHN
N/A
Manufacturing Process:
I'ANCO square profile long link chains are manufactured using cast Manganese and Alloy steels. With both of these materials, accurate chemistry and heat treatments are critical. All of the castings used by I'ANCO are checked for chemical composition before the metal is poured into the molds. This ensures that the exact physical properties required can be achieved during heat treatment.
The proper heat treatment process is crucial to the performance of any steel. The furnaces used to treat I'ANCO castings are all operated through PLC units and the transport times from the furnace to the quench tank are kept at less than 30 seconds to ensure a complete quench.
All of the castings are then inspected for any defects prior to sending them to the shop for assembly. After the austenitic manganese chain has been assembled it is then sent to the Rumbler for initial impact hardening. The final quality test performed on the chain is a proof-load; where the chains are pull tested to twice their normal working loads.
Welding Austenitic Manganese Steels
1. PREPARATION
Steel should be clean and free of rust, oil, etc.
Do not preheat, however, materials should be at least 50 degrees F. If welding in sub-zero temperatures, then material should be brought up to above freezing.
2. ELECTRODES
Similar Metals:
Stick: Postalloy 205 or equivalent, 5/32" diameter, 140-180 amps
Wire: Postalloy 2850 or equivalent, 1/16" diameter, 150-230 amps
Dissimilar Metals
Stick: 309 MO LTI stainless steel, 5/32" diameter, 100-125 amps
Wire: 309 MO LTI stainless steel, 1/16" diameter with CO2 shield, 225-250 amps
3. WELDING
The critical temperature of austenitic manganese steel is 750 degrees F.
Temperature adjacent to the weld should not exceed 600 degrees F after one minute.
When possible, skip weld or make several passes to keep heat down. Immediate peening is recommended, as it will reduce internal stresses during cooling.
Use reverse polarity.
Hold electrode vertically for welding work hardened manganese steels. Choose the lowest possible amperage and cool the work piece to be surfaced at the same time.
4. GENERAL
Austenitic manganese steel, also known as "Hadfield" manganese is for all intents and purposes, "nonmagnetic"
As manganese steel is rarely used in structural applications, good sound and practical procedures will produce satisfactory weld joints or attachments.
As drilling of austenitic manganese steel is almost prohibitive (it work hardens), welding is the most often used method of attaching manganese steel plate and bar stock. If precise bolt hole or countersink location is required, then electric discharge machining (EDM) should be used.
