October 25, 2021

News Release
New Lineup of Nickel- and Molybdenum-free High Strength Case-hardening SteelSanyo Special Steel Develops ECOMAX5 for Omitting or Simplifying Parts
Manufacturing Processes— Contributes to reduction of cost and CO2 emissions when manufacturing high-strength parts
such as gears and shafts —Sanyo Special Steel Co., Ltd. (President: Katsuhiro Miyamoto; Head Office: Himeji, Hyogo Prefecture) has
developed ECOMAX5 as a new addition to its proprietary ECOMAX series of nickel- and molybdenum-freehigh-strength case hardening steels. The developed steel meets the expectations for compact and lightweight
designs of parts with excellent strength, which is a prominent feature of the ECOMAX Series. It also features anew alloy design that enables customers to omit or simplify their parts manufacturing processes, thereby
contributing to the reduction of CO 2 emissions, which has recently become increasingly desirable in terms oflife cycle assessment (LCA).
In addition to having equivalent or higher strengththan the existing ECOMAX series, ECOMAX5 has further
enhanced properties sought by customers who want to omit
or simplify various heat treatment processes (annealing,normalizing, carburizing) in their parts manufacturing
process. Not only does this allow customers to reduce costs,
it promises to contribute to drastic reductions in CO 2emissions.
- ECOMAX5 is expected to be used for gears and shafts
Contributions to the miniaturization and weight
reduction of automotive parts such as gears andshafts
Parts that require high strength are typically made from materials with added orincreased amounts of rare and costly alloy elements such as nickel and molybdenum. TheECOMAX series, including ECOMAX5, is based on high-cleanliness steelmaking
technology that maximizes the inherent performance of steel. By optimizing the balanceof alloy elements such as chromium and silicon, and the operating conditions during thesteelmaking process, ECOMAX5 achieves significant strength improvements despiteusing less alloys. It achieves more than five times the life of typical case hardened steel(JIS SCM420), particularly against peeling damage (pitting corrosion) on gear teeth
surfaces. The improved fatigue strength of parts promises further downsizing and weight
reduction of various mechanical units, including those for automobiles.
- Anti-pitting characteristics ofECOMAX5Contributions to the reduction of CO2 emissions by simplifying or omitting parts processes
In parts manufacturing processes that use case hardening steel, when cold forging, a heat treatment process called "annealing"is used to soften the material. To anneal alloy steels such as case hardened steel, the material is usually heated to about 800°C until
it becomes an austenite structure, and then slow-cooled over a long period of time to precipitate spherical carbides, which softens
the material. With ECOMAX5, carbides spheroidize and soften in less than half the processing time of conventional methods
without slow cooling by holding the material in the low temperature range for a short time.
In addition, the presence of evenly dispersed
spherical carbides due to annealing facilitates
high-precision forming in cold forging andimproves compatibility with near net shaping.
Additionally, because of its superior properties
forpreventing
graincoarsening
duringcarburization compared to typical case hardened
steels and other grades in the ECOMAX series, thenormalizing process—usually applied after cold
forging and before carburizing and quench—canbe omitted, and the processing time can be greatly- Simplification and omission of the manufacturing process for
reduced due to higher carburizing temperatures.
gear and shaft parts (example)

Sanyo Special Steel will continue to develop eco-products, which are products that allow the manufacture of smaller and lighterparts while reducing CO2 emissions, in order to meet the sophisticated and diverse needs of customers toward a decarbonizedsociety.
EndFor inquiries: General Affairs PR Group, Sanyo Special Steel Co., Ltd., (Phone: +81 79-235-6002)

(Reference)High strength (fatigue life) while saving scarce resources
Pitting strength greatly affects the service life of gear parts used in automotive drivetrain units. Pitting is a phenomenon thatoccurs when gear teeth and their counterparts repeatedly come into contact with each other under high stress with slippage,causing cracks to form and propagate on the gear tooth surface due to metal fatigue, eventually leading to fracture. Thisphenomenon is expected to become increasingly important as the use of low-viscosity lubricants aimed at improving fuelefficiency and the use of high speed motors in electric vehicles gain momentum. In order to reduce the damage caused by thisphenomenon, adding rare resources such as nickel (Ni) and molybdenum (Mo) are said to be effective in improving the softening
resistance to temperature rises during contact with the tooth surfaces.
The high pitting fatigue life of ECOMAX5 was achieved by optimizing the amount of silicon (Si) and chromium (Cr) without
using rare metal resources such as nickel and molybdenum, and by giving it higher softening resistance than typical case hardened
steel, and properties that prevent cracks from initiating in the surface layer of carburized parts.
Achieves outstanding fatigue strength andConceptual diagram and external view of gear pitting corrosion
PittingStarting
point

1 mm

Gear
teeth
· Drastic reduction of annealing time and prevention of forging cracks
In manufacturing processes that use typical case hardened steel, annealing is performed to soften the material before cold
forging. This heat treatment requires a long period of time, from 12 to 24 hours, under precise temperature control, because thestructural changes in the steel need to be properly controlled.
ECOMAX5 leads itself to the shortened annealing method, which is unparalleled elsewhere in the world, to soften steel in ashort period of time at a relatively low temperature that does not cause structural in typical case hardened steel. This promises tohalve the existing processing time (6 to 8 hours).
Structure of annealed material (optical microscope)
Uneven distribution of carbides in the annealed(Uneven distribution of carbides)(Uniform distribution of fine carbides)
structure will lead to uneven deformation during coldforging, making the material prone to cracking.
The annealing process of ECOMAX5 forms astructure in which carbides are evenly dispersed,
20 μm
20 μm
making it less likely to crack during deformation, andthus making it easier to achieve near netting in
ECOMAX5
Typical caseapplications such as gear tooth forming.
hardened steel(JIS SCr420)· Excellent grain coarsening resistance
Crystal grains of parts carburized and quenched after cold forging
With typical case hardened steel, direct carburizing(optical microscope photo)and quenching after cold forging coarsens the crystal>(Maintains fine crystals even aftergrains, and causes the strength and toughness of the part
(Coarsening of crystallite by carburizing)
carburizing)
to weaken. To prevent this, a heat treatment called
normalizing was indispensable before carburizing andquenching.
ECOMAX5 appropriately precipitates niobium (Nb)carbonitrides in the steel, which are fine pinning grains
50 μm
50 μm
that inhibit grain coarsening, and the alloy design
Typicalcase
ECOMAX5enhances the homogeneity of the structure before
hardened steel
carburizing. This causes the crystal grains to remain(JIS SCr420)
stable in a fine state even during carburizing andquenching, which allows the previously required
normalizing process to be omitted.
In addition, these excellent properties enable the application of high-temperature, short-time carburization, which shortens theoverall processing time by increasing the carburizing temperature.
End