KVA STAINLESS™ has developed a portfolio of patents and proprietary technology for forming lightweight, high-strength, structural components for transportation vehicles using martensitic stainless steel alloys. These technologies contribute to the direct reduction in manufacturing costs relative to the implementation of conventional lightweighting methods and materials – for stamped, welded or tubular components.
Automakers are looking for ways to make vehicles lighter and yet safer; as a result, several new materials such as carbon fiber, aluminum, magnesium, titanium and thermoplastics have been introduced to the industry. Making cars and trucks lighter helps increase fuel economy, and making them safer reduces fatalities caused by serious collisions.
KVA STAINLESS™ believes that the next material should be martensitic stainless steel.
KVA STAINLESS™ has spent years testing and developing patented technology to produce stamped structural components as well as welded shapes for automobiles and trucks with characteristics that are strong and lightweight – yet, they can be produced at low costs. KVA's technology focuses on manufacturing original equipment and aftermarket automotive structural members such as vehicle pillars, sub-frames, cross beams, frame rails, frame brackets, roof rails, seat frames, seat rails, door beams, bumper beams, control arms, instrument panel reinforcements, running boards, roll-bars, tow hooks, bumper hitches, roof racks and numerous other applications. In addition to stamped structures, tube-based components can be fabricated with KVA's seam welded tubing technology: including fuel injection components, hydraulic lines, interior seat frames, exhaust systems, side steps, and roof railings.
Vehicle designers and manufacturers are trying to reduce the overall body mass of vehicle to improve fuel economy by developing structural members and components that are lightweight and of sufficient strength and durability to meet automotive safety requirements. In addition, automotive structural members must be able to contend with harsh environmental conditions, and thus must be corrosion and wear resistant.
In cost-sensitive applications such as automobiles, conventional engineering materials force a trade-off between cost and performance: measured by fuel efficiency, safety, and/or durability. Consequently, the typical vehicle tends to have a frame that is too heavy. A heavy frame requires a more powerful engine, which leads to higher fuel consumption and higher emissions. Having a more powerful propulsion system increases the manufacturing costs, uses more material, requires more energy to produce, which increases the emissions in the manufacturg process and necessitates an even heavier frame to support itself. Conversely, a lightweight, weak frame compromises the durability of the vehicle and the safety of its occupants.
Present day automotive structural members are still undesirably heavy – or – expensive to manufacture. The automotive industry has recently introduced new alloys into automotive structures to improve strength in an effort to reduce weight. Furthermore, complicated and expensive coatings and heat treatments have been introduced to improve the characteristics of corrosion resistance, hardness, tensile strength, and toughness. When alternative materials are used to perform lightweighting, studies have found that on average, weight reduction would cost $2 to $3.50 per kg of weight saved (Bandivadekar, 2008).
The aforementioned attempts at manufacturing lightweight structural automotive components still suffer from various drawbacks. For example, prior manufacturing processes are either too expensive or produce automotive structural members having characteristics which are less than desirable such as a lack of strength, durability, corrosion resistance, etc. Structural materials are currently available in a broad range of strength-to-weight ratios, or specific strengths, but the cost of these materials generally increases disproportionately to their specific strengths. Carbon composites and titanium, for example, while being perhaps ten times stronger than mild steel for a given weight, are typically more than fifty times more expensive when used to bear a given load. Consequently, such high performance materials are typically used only in on small items or in applications where the high cost is justified, such as in aircraft.
Generally, automotive structural members are manufactured from non-air hardenable steels. A rare exception to this is boron-treated steel, which provides high strength after a hot-stamping forming process. In this process, parts are formed in a red-hot superplastic state, and cooled within the stamping dies to harden the material. However, the hot-stamping process equipment requires a substantial capital investment – and the resulting parts typically require scale removal and are no more corrosion resistant than mild steel.
Air hardenable martensitic stainless steels are extremely affordable and have exceptionally strength, particularly compared to metals such as aluminum and even titanium. Experimentation with air hardenable stainless steel for automotive structural applications appears to have never been attempted due to the paradigm shift in thinking required to produce a high-strength automotive part. Historically, high-strength automotive applications relied on the evolutionary approach of forming ferrous alloy strip, in its final metallurgical microstructure, using successively higher strength steels as the raw material until either the strength targets were met or the part could not be formed due to the material's limitations.
Air hardening steels were first commercially developed for use in cutlery for their high hardness and excellent wear resistance. Common air hardenable steels include martensitic stainless steels.
Air hardenable martensitic stainless steels possess a relatively high carbon and low chromium content compared to other stainless steels. Additionally, little to no nickel is present, keeping material cost and volatility low relative to higher alloyed stainless grades. According to American Iron and Steel Institute (AISI) standard definitions, standard air hardenable martensitic stainless steels types include 403, 410, 414, 416, 416Se, 420, 420F, 422, 431, 439, and 440A-C.
The relatively high carbon content compared to other stainless steels results in steel with the ability to harden via heat treatment to a high strength condition. Good corrosion resistance is obtained due to the protective chromium oxide layer that forms on the surface. Unfortunately, the high carbon and chromium has historically presented difficulties related to brittleness and cracking in welding, and accordingly martensitic stainless steel has been primarily used for cutting tools, surgical instruments, valve seats, and shears. Non-stainless air hardenable steels, which contain very high levels of carbon to allow the formation of a martensitic microstructure upon quenching, also present difficulties related to brittleness and cracking upon high-speed welding.
This ongoing lack of a strong and lightweight - yet low cost - automotive structural material is a main hindrance to the development of economically viable low emissions vehicles that can compare in performance, safety, comfort, and price to those powered by the typical internal combustion power system.
Thus, rather than resort to the use of expensive alloys, it would be beneficial to use KVA's patented technology to reduce manufacturing costs, enabling automotive structual members to be lightweight, high-strength, and corrosion resistant.
Ideal automotive applications for KVA STAINLESS™ processed martensitic stainless steel include:
Here are some of the products which have benefited from KVA STAINLESS™ Martensitic Stainless Steel Technology: