Ajax Electric Company - Manufacturers of Salt Bath Furnaces Martempering & Austempering

Ajax Electric Co. Industry's First choice in Salt Bath Systems

A big problem in heat treating low alloy steels of various sizes and sections is the development of quench cracks, distortion and dimensional changes.

Interrupted quenching in a salt bath can eliminate these undesirable by-products.

Thermal and transformational stresses in heat treating are illustrated by Time-Temperature-Transformation data,commonly referred to as TTT Curves or "S" Curves.

By controlling quenching severity, austempering and martempering provide a cooling rate ahead of the nose of the S-curve so that the work reaches the optimum isothermal quench temperature without undesirable higher temperature transformation properties.

Reduce manufacturing costs and improve metallurgical results with Salt Baths designed for Austempering
&
Martempering

AJAX considers four primary factors when designing quench furnaces for batch and in-line processing:

1. Bath Temperature Uniformity - This is essential for consistant metallurgical properties. Heavy duty or light duty, gas or electric, AJAX furnaces provide temperature control within ±5°F.
2. Proper Agitation of the bath - Constant or variable speed propeller agitation provides uniform flow to quickly and efficiently remove heat from the work.
3. Removal of bath contaminants - A continuous filtering and dumping system - The AJAX Sludge Dumper - removes contaminations, such as chloride salts, from the furnace for maximum quenching efficiency.
4. Water addition to the quench bath - Manual and automatic systems are available to adjust frequency and duration of small water additions which can increase quenching power, permit isothermal quenching of heavier sections, or give a faster cooling rate.

In Austempering, austenitic steel is cooled at a sufficient rate to avoid the nose of the S-curve, and held just above the start of martensitic transformation (Ms point) for complete transformation to a bainitic structure while the temperature remains constant - thus alleviating thermal and transformational stresses that could cause cracking or distortion.
Austempering involves less heat treatment time and is preferred when fast turnaround is a prime consideration.

The
Advantages of
Salt Baths

Negligible Distortion

Superior Toughness & Ductility

Prevention of Quench Cracks

Higher & more uniform Hardness

Hardening of Heavier Sections

In Martempering, austenitic steel is also cooled at a sufficient rate to avoid the nose of the S-curve, preventing the start of pearlitic or bainitic transformation. The Martempering temperature is selected just above the Ms point. When the temperature is uniform throughout the steel, it is cooled in air to room temperature. During cooling martensite forms. Thermal and transformational stresses are lowest.
Martempering produces a minimum of strain on heavy sections.

AJAX Electric Company
60 Tomlinson Road
Huntingdon Valley, PA. 19006 U.S.A.
Phone: (215) 947-8500 • (800) 516-9916 • Fax: (215) 947-6757