Specialty Alloys Key to Many Automotive Advances
Many of the technological advances that will drive the automotive industry in the twenty-first century will depend on high- performance specialty alloys. Designers and engineers have relied consistently on these materials to provide the special, often demanding properties required for critical applications.
High consumer expectations, environmental concerns, more stringent regulations, safety and the growing electrification of new cars and trucks are forcing manufacturers to focus on durability, maintenance-free operation and the development of new technologies.
Specialty alloys have played, and will continue to play, a key role in meeting these demanding requirements. By conservative estimate, there are more than 100 applications for specialty alloys in the average new car. Most of them are vital to the operation and performance of the vehicle.
More efficient, hotter running engines require specialty alloys with greater strength and heat resistance. Alloys with superior corrosion resistance are needed for harsh oxidizing liquids, alternative fuels and emission control systems. Special electrical and magnetic alloys are essential for sensors, solenoids, computers and controls. The quest for fuel efficiency, and pollution controls dictates the use of specialty alloys.
Dozens of grades qualify as specialty alloys used by the automotive industry. Progressively more of them are produced by premium melting practice to optimize properties and performance.
Alloys made by powder metallurgy have been used more frequently because they offer producers of automotive parts and components impressive benefits such as: refined microstructure, increased productivity, lower-cost production, less downtime, improved product uniformity, and more consistent behavior.
From more than 400 specialty alloys, Carpenter provides a full range of alloys that have been used by the automotive industry, including magnetic alloys, stainless steels, high temperature alloys, powder metal high speed tool steels, and both hot- and cold-work tool steels.
The trend toward more electronic controls has stimulated development of a variety of magnetic alloys that are needed to optimize the output and response time of electro-mechanical components in automotive vehicles.
Electrical irons, for example, have been used for magnetic circuit cores and relays, and solenoids that activate electrical controls. Silicon irons offer various levels of electrical resistivity, with collateral magnetic properties. Chromium-iron magnetic stainless steels provide good corrosion resistance for devices exposed to weather, fuel or other corrosive environments.
Chrome-Core® alloys provide various combinations of corrosion resistance, magnetic properties, cost and fabricating characteristics. High-permeability nickel-iron alloys are used wherever high flux density or high magnetic strength is required with low magnetizing force.
In general, magnetic alloys have been used for engine and fuel handling components such as fuel injector cores, armatures and inlet tubes. Silicon irons and electrical irons have been used for ABS solenoids and pole pieces, and controlled expansion alloys have been used in electronic flashers.
High temperature alloys, known for their contributions to the aerospace industry, have been used increasingly in automotive applications, particularly for exhaust valves and bolts. Alloy modifications are available which offer benefits in either lower cost or improved performance. Valve steels have offered excellent combinations of corrosion resistance and strength at elevated temperatures.
A large number of specialty stainless steels have been used for applications requiring various combinations of corrosion resistance and strength. Typical of the many applications are: engine and fuel handling components (armatures, pole pieces and inlet tubes in EFI), parts for exhaust systems and pollution control (hardware in catalytic converters, manifold bolts and studs, EGR components and oxygen sensor parts), instrumentation controls (shielding for electronic components, and components for dashboard gages) and a wide number of functional and decorative applications (shafts for power window components, cruise control components and electromechanical sensors for air bags, and antenna bases).
Specialty powder metal high speed tool steels and hot-and cold-work tool and die steels have been used for important tooling applications in the automotive industry. Powder metal high speed tool steels typically have been used for form tools, broaches, shave cutters and gear cutting hobs. Hot-work tool steels have been used for extrusion dies, die casting dies, forging dies and hot piercing punches. Stamping dies for frames and other structural components require cold work dies. Other grades offer various combinations of high strength and toughness for applications where tool breakage had been a problem, and where high strength and corrosion resistance are needed.
By William A. Wellock
Carpenter Technology Corporation