Heat Treatments

Heat Treatments

At McKees Rocks Forgings, we use a heat treatment process to refine and improve the overall structure of our steel.  

There are many benefits of this treatment including:

  • Adding longevity to your product
  • Refining grain size
  • Improving strength and machinability due to uniformity
  • Removing residual stresses

Crane Wheel Heat Treatments

The heat treatment of crane wheels can be completed several ways depending on your application. Learn more about the different possibilities in the fields below.

Rim Toughening

This process involves uniformly heating the entire wheel and then selectively quenching the rim while the wheel is spinning.  The most common hardness range for wheels heat treated in this manner is 321-363BHN, but other ranges can be achieved as well.  Common ranges are taken directly from “ASTM A-504 Class C” and “AIST Technical Report #6, Allowable Wheel Loads Guide for Heat Treated (320BHN Minimum) Crane Wheels”.  The level of hardness achieved using this process creates an extremely tough and durable wheel for moderately loaded wheel applications.

Recommended Usage:

  • Cranes with moderate wheel loads as defined in the “AIST Technical Report #6, Allowable Wheel Loads Guide for Heat Treated (320BHN Minimum) Crane Wheels”.
  • Applications with high flange impact loads due to large rail joint gaps.
  • Applications with consistently high flange pressure due to severe end truck or rail misalignment – these flanges will bend rather than break.

 

Deep Hardened 1070MOD

The deep hardening heat-treating process produces crane wheels, industrial car wheels, sheaves, and rollers with a surface hardness up to 60 Rockwell C-scale. This process involves the full normalizing of the forging followed by a selective heating of the rim area and then aggressive quenching in a polymer solution.

The depth of hardness produced in this process exceeds that which is produced by the traditional carburizing process and meets or exceeds the depth of hardness requirements of the AIST Technical Report #6, for Case Hardened Wheels.

The hardness level and depth of hardness achieved in this industry leading process provides the maximum load bearing capability and abrasion resistance for any of the processes that we offer.

This process yields the best sub-surface hardness depth in the wheel tread of any case hardened wheel, which gives it the maximum resistance to tread spalling.

Recommended Usage:

  • Cranes with extremely high wheel loads as defined in the “AIST Technical Report #6, Allowable Wheel Loads Guide for Case Hardened (56-60RC) Crane Wheels”.
  • Cranes or industrial cars that operate in areas with high levels of abrasive dust, dirt, or other abrasive environments.
  • Applications with reasonable end truck and rail alignment that can take advantage of the significant depths of hardness in the tread and flange.

 

Differentially Hardened

The differentially hardening heat-treating process produces crane wheels, industrial car wheels, and sheaves with a tread and inner flange surface hardness up to 60 Rockwell C-scale (RC).
This process involves the full normalizing of the forging followed by a selective heating of the rim and inside flange area and then aggressive quenching in a polymer solution.

The depth of hardness produced in this process exceeds that which is produced by the traditional carburizing process and meets or exceeds the depth of hardness requirements of the AIST Technical Report #6, for Case Hardened Wheels.

By only heating the inside of the flanges, the core and outside of the flanges remain ductile and resistant to breakage.

This process yields the best combination of maximum wheel load bearing capability and flange toughness in the industry.

Recommended Usage:

  • Cranes with extremely high wheel loads as defined in the “AIST Technical Report #6, Allowable Wheel Loads Guide for Case Hardened (56-60RC) Crane Wheels”.
  • Applications with questionable end truck and rail alignment that may cause crane skewing resulting in significant flange pressure.
  • Older cranes that have lost the ability to track correctly during normal operation, which results in significant contact between the wheel flanges and rail head.

 

Super Tough AISI-4140

The AISI-4140 “Super Tough” Crane Wheel is capable of supporting extremely high wheel loads while still maintaining superior flange toughness and ductility. This process involves the full normalizing of the forging followed by a selective heating of the rim area and then aggressive quenching in a polymer solution.

The alloy steel allows for significantly greater toughness and impact resistance than a similar hardness carbon steel wheel. Laboratory testing also shows that flanges of AISI-4140 “Super Tough” Wheels have 50% greater flange strength and 50% greater impact strength than carbon steel wheel flanges.

The increased hardenability of the alloy steel allows for deeper hardness penetration and increased spalling resistance. The depth of hardness achieved with the “Super Tough” wheel is 50% greater than with a carbon steel wheel (greater than 40RC at 0.350in).

It is available in a variety of hardness ranges up to 56RC (575BHN) to meet your most demanding needs.

Recommended Usage

  • Older cranes with poorly aligned runways.
  • Applications with heavy loads and high flange wear.
  • Applications that have experienced flange breakage.

 

Additional Heat Treatments

We also offer additional treatments depending on your application. Learn more about the different possibilities of these treatments in the fields below.

Normalizing
This heat treatment process is used to refine the overall structure of the steel and has many benefits including:  

  • Increased strength
  • Improved machinability
  • Refined grain size
  • Removed residual stresses

 

Normalizing and Tempering

This heat treatment process has all the benefits of normalizing.  Some alloys tend to have a higher hardness or residual stresses even after normalizing. The added temper cycle further removes any residual stresses, improves toughness, and lowers the hardness.

Normalizing, Quenching, and Tempering

This heat treatment process has all the benefits of normalizing which prepares the material for hardening.  The next step is reheating to a temperature slightly lower than the normalizing temperature, called Austenitization, to prepare for the quenching operation.  The quenching operation rapidly cools the part to harden it significantly. This can be done in water or polymer depending on the type of part or geometry.  The final step, tempering, is performed at a predetermined temperature to tailor the hardness achieved. Tempering can be done to provide both strength and hardness depending on the alloy and application.

Solution Treating and Age Hardening 

Stainless steel alloys, such as 17-4PH, require a solution heat treatment similar to normalizing, where the structure of the metal is homogenized, machinability is improved, grain size is refined, and residual stresses are removed.

The age hardening process is completed at lower temperatures, sometimes even after rough or final machining due to the low distortion or surface changes experienced with age hardenable alloys. The age hardening process temperature is tailored to meet exact strength and hardness requirements.

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