Inspectioneering
Explore this topic

Overview of Spheroidization (Softening)

Spheroidization describes a specific change that can occur in the microstructure of carbon and low alloy steels exposed to temperatures from 850°F – 1400°F (440°C – 760°C). This change may result in a loss of mechanical strength and/or resistance to creep.

When exposed to the susceptible temperature range, the elements that strengthen steels (carbide phases) can become unstable and begin to group together, which reduces the strength of the material. At higher temperatures, spheroidization can begin to affect the steel within a matter of hours. At lower temperatures though, spheroidization can take years to have a noticeable effect on the material.

Fortunately, spheroidization isn’t too serious of an issue in most circumstances. The loss of strength is usually minor and doesn’t create any safety issues that might compromise operation of equipment.

In certain rare high temperature situations, the loss of strength can be significant enough (~30%) to result in a reduction in design margin of the equipment. In these cases, fitness for service assessment should be performed to determine the proper course of action.

Expert Insight

The following is from 99 Diseases of Pressure Equipment by John Reynolds. Read the full article here.

Spheroidization is a rather technical term that describes a metallurgical aging phenomena that results in loss of mechanical and creep strength. It occurs when carbon and low alloy steels are exposed to temperatures in the range of 850°F - 1400°F (440°C - 760°C) where carbide phases (the strengthening element of steels) become unstable and begin to agglomerate, which then results in the loss of strength. At the upper end of that temperature range, spheroidization can occur within hours, while at the lower end, it may take years; so it is clearly another of our time- temperature degradation phenomena.

Spheroidization is not much of threat to our pressure equipment, except in some unusual circumstances. Usually the loss of strength is relatively minor, but under some high temperature conditions can cause a 30% reduction in strength. However, that loss of strength usually results in some reduction in design margin, which can sometimes be acceptable for continued safe operation with appropriate fitness-for-service analysis. If it’s not acceptable, then derating is usually the result. The unusual conditions where spheroidization could be a threat involve high stress intensification factors, high applied stresses, or in combination with other degradation or flaws...

Continue reading...

Is this definition incomplete? You can help by contributing to it.

Share this Topic

Related Topics

Amine Stress Corrosion Cracking (SCC) Ammonia Stress Corrosion Cracking Brittle Fracture Carburization Caustic Stress Corrosion Cracking (Caustic Embrittlement) Cavitation Chloride Stress Corrosion Cracking Cooling Water Corrosion Corrosion Fatigue Corrosion Under Insulation (CUI) Cracking Decarburization Embrittlement Erosion Corrosion Fatigue (Material) Graphitization High Temperature Hydrogen Attack (HTHA) Hydrochloric (HCl) Acid Corrosion Hydrofluoric (HF) Acid Corrosion Hydrogen Blistering Hydrogen Embrittlement Hydrogen Induced Cracking (HIC) Hydrogen Stress Cracking Liquid Metal Embrittlement (LME) Metal Dusting Microbiologically Induced Corrosion (MIC) Naphthenic Acid Corrosion (NAC) Phosphoric Acid Corrosion Polythionic Acid Stress Corrosion Cracking (PASCC) Stress Assisted Corrosion Stress-Oriented Hydrogen Induced Cracking (SOHIC) Sulfidation Corrosion Sulfuric Acid Corrosion Thermal Fatigue Vibration Fatigue Wet H2S Cracking
Articles about Spheroidization (Softening)
  • September/October 2005 Inspectioneering Journal
    By John Reynolds at Intertek

    Spheroidization is a rather technical term that describes a metallurgical aging phenomena that results in loss of mechanical and creep strength. It occurs when carbon and low alloy steels are exposed to temperatures in the range of 850F - 1400F (440C - 760C) where carbide phases (the strengthening element of steels) become unstable and begin to agglomerate, which then results in the loss of strength.

    Companies
    Videos related to Spheroidization (Softening)
      White Papers related to Spheroidization (Softening)
        Downloads & Resources related to Spheroidization (Softening)
          Events related to Spheroidization (Softening)
            News related to Spheroidization (Softening)

              Inspectioneering Journal

              Explore over 20 years of articles written by our team of subject matter experts.

              Company Directory

              Find relevant products, services, and technologies.

              Job Postings

              Discover job opportunities that match your skillset.

              Case Studies

              Learn from the experience of others in the industry.

              Event Calendar

              Find upcoming conferences, training sessions, online events, and more.

              Industry News

              Stay up-to-date with the latest inspection and asset integrity management news.

              Blog

              Read short articles and insights authored by industry experts.

              Acronyms

              Commonly used asset integrity management and inspection acronyms.

              Asset Intelligence Reports

              Download brief primers on various asset integrity management topics.

              Videos

              Watch educational and informative videos directly related to your profession.

              Expert Interviews

              Inspectioneering's archive of interviews with industry subject matter experts.