lamellar pearlite

Pictured Above

SEM micrograph of lamellar pearlite in an eutectoid (0.8% carbon) steel after annealing.

Process Annealing

Also refered to as intermediate annealing, subcritcal annealing, or in-process annealing this process restores the ductility of a metal to allow further cold working. This process is suited to low-carbon steel and is primarily carried out on cold rolled steel.

Full Anneal

Also referred to as LP annealing (lamellar pearlite), material can be fully annealed to make make it easier to machine. Full annealing results in material that has a lower yield and tensile strength but is much more ductile. Material often undergoes another heat treatment process after it is machined to restore or increase its strength.

Pictured Left

SEM micrograph of lamellar pearlite in an eutectoid (0.8% carbon) steel after annealing.



Pictured Above - Bainitic zone in welding of DQSK (draw quality semi-killed) steel (mild steel)

Austempering Phase Diagram

Pictured Above - Time-temperature transformation diagram where cooling (red) curve shows an austempering process.


Austempering is a heat treatment process that is most commonly used to improve mechanical proporites and/or eliminate distortion. It offers a number of advantages over conventionally quenched and tempered ferrous metals. In steels above 40 HRC these improvements include:

  • Higher ductility, impact strength and wear resistance for a given hardness,
  • A low distortion, repeatable dimensional response,
  • Increased fatigue strength,
  • Resistance to hydrogen and environmental embrittlement.

Cast Irons (from 250-550 HBW) enjoy similar improvements including increased wear resistance for a given hardness. They do not benefit from increased resistance to hydrogen embrittlement.

Austempering result in significant cost and time savings over conventional quench and temper processes. Products made from steel may be machined before austempering due to the low distortion of the process. Austempered cast iron products may also provide an alternative to quench and tempered steel components resulting in substantial savings.

Austempered steel was first used in rifle bolts during World War II. It is commonly used on thin alloy steel parts which require better elasticity such as springs, clips, and clamps. Additional common uses include, but are not limited to: seat belt components, bearings, mower blades, transmission gears, wave plates, turf aeration lines.

Carbon Restoration

Carbon Restoration

This process is used to restablish the correct carbon content on the surface of a steel part. This process is recommended for parts that require high mechanical performance.



Carbonitriding is a heat treatment process that results in increased surface hardness of a part, which decreases surface wear. It is often applied to inexpensive, easily machined low carbon steel. The process absorbs nitrogen into the surface of the part which diffuses with carbon; hence the name carbo-nitr-iding. The case depth is typically between .05 to .07 mm thick. Compared to carburizing; carbonitriding has greater resistance to softening during tempering and increased fatigue and impact strength. However, carbonitriding is costly to perform at higher case depths and is sometimes used in tandem with carburizing.

Common applications include: gear teeth, cams, shafts, bearings, fasteners, pins, hydraulic pistion rods, automotive clutch plates, tools, dies, and tillage tools.

Carburizing / Casehardening

Case Hardening - Chain

Carburizing, sometimes referred to as casehardening or facehardening is a process that adds carbon to the surface of a low-carbon steel or iron. This results in a part with increased surface hardness while remaining soft beneath.

Common applications include: firing pins, rifle bolt faces, engine camshafts, self-drilling screws, lock shackles, and chains.

Neutral Hardening

Netural hardening is also referred to as martensitic hardening or quench hardening. Parts that are neutral hardened keep the same chemical surface on the steel surface but achieve a high strength. Depending on the steel type, a number of benefits can result including:

  • High Strength, toughness, and temperature resistance,
  • Enhanced machinability with respect to surface roughness,
  • Corrosion resistance in the case of martenstic stainless steels.

Common applications include: drive shafts, carrier bars, frames, nuts and bolts, lifting eyes, cutting, hammering, or rolling tools, cutting and stamping dies, and stainless steel parts.


Normalizing is one of the least costly and common heat treating process for metals. Normalizing is often applied during the production of hot rolled steel products such as railroad wheels, bars, and axles. Normalized metals have a more uniform microstructure than unprocessed steel that results in higher ductility and toughness.

The process is similar to annealing except that the material is air cooled which results in much quicker cycle times at heat treat. Compared to full annealing this process produces a harder but less ductile material.


In addtion to air quenching, Co-Op Thermal offers polymer, oil, and water quench. Each process offers its own advantages and is heavily dependent on the material being quenched.

In-House Lab

Hardness Tester

CO-OP THERMAL has an in house lab which improves turn around times. We an assortment of equipment including hardness testers, and puck mounting presses. We offer certification to required specifications with all of our services.