Heat Treatment
A key benefit of KVA technology is the ease of forming complex part geometries. The material can be readily formed in its softer, annealed state, with low force, low cost tooling. Once the desired geometry is created, the parts can be heat-treated to a high-strength condition with low-cost thermal processing methods.
High Strength Alloys
Many industries are transitioning to higher strength alloys in order to improve product strength and/or reduce product weight. Unfortunately, these high strength alloys are not always compatible with existing fabrication methods, particularly forming and welding. Higher strength steels typically suffer from limited formability and require heavier and larger presses and tooling. Part springback, blank tearing, splitting, wrinkling and die breakage are not uncommon, resulting in reduced productivity and product performance.
An alternate route to high strength products involves forming with the material blanks in a low strength, annealed condition, then heat treating the formed geometry to a high strength, hardened state. Many heat-treatable alloys require substantial thermal processing times in batch-type furnaces. Additionally, severe quench (cooling) rates are needed for common alloys - the thermal shock of rapid quenching in water or oil is messy, expensive and distortion inducing - and not ideal for thin-walled weight sensitive applications. These methods have traditionally been cost prohibitive for widespread use, and hence, have been limited in application.
General Types of Distortion:
- During fast heating
- During fast cooling
- Due to stresses while at heat (creep)
- Due to residual stresses
- During phase transformation
- Due to dissimilar metals
KVA Heat Treatment Technology
KVA founder, Mr. Ed McCrink, has been pioneering the development of low-cost, high-quality thermal processing methods since the 1950s as the founder and CEO of Hi-Temp, Inc., which specializes in continuous thermal processing of hardenable stainless alloys. Mr. McCrink's experience, combined with the innovative spirit of KVA development staff, has resulted in numerous patented thermal processing technologies enabling low-cost martensitic stainless steel (MSS) products.
KVA proprietary, simple to implement methods eliminate conventional heat treating difficulties, such as long cycle times and excessive, unpredictable part distortion. The material can be readily formed in its softer, annealed state, with low force, low cost tooling. Once the desired geometry is created, parts and entire assemblies can be heat treated to uniform microstructures and hardness/strength levels tailored to the individual application. Components can be hardened to uniform, high-strength conditions throughout, with no loss of strength in areas welded prior to hardening.
Key advantages of KVA heat treating technology:
- Simple air-quench processes
- Minimal distortion
- Uniform properties throughout part
- Minimal part-to-part variation
- Continuous or batch processing
- Improved ductility
- Enhanced toughness
KVA processed MSS are ideal substitutes for boron-treated steels in hot stamping operations, or alternatively can be thermally processed with efficient, high throughput continuous furnaces or induction methods. Compared to forming pre-hardened thermomechanically processed alloys, such as dual phase (DP) advanced high strength steels, forming ductile, annealed MSS is very straightforward.
The unique air-hardening property of MSS allows for hardening to be performed, with minimum distortion due to the slow cooling rates involved - versus conventional water or oil quench methods which induce significant thermal shock, distortion and residual stresses on parts. The result is that heat-treated MSS can now be used in a wide variety of structural applications, without significant cost increases.
Similar to low-alloy steels, maximum strength and hardness of thermally processed MSS primarily depends on carbon content. Low carbon MSS grades, such as AISI type 410, have tensile strengths in excess of 200 ksi (1400 MPa) in the fully hardened condition. Tensile strengths in excess of 300 ksi (2100 MPa) are possible in the higher alloyed MSS grades.
Ideal applications for KVA thermal processing technology include:
- Tubing Solutions
- Structures
- Automotive components
- Bicycles
- Heat exchangers
- Renewable Energy
- Transport, Gas and Oil Production/Pipelines