NI-SFT spiral tap achieves stable tool life in heat-resistant alloys
Vis Huang | OSG Shanghai
Furious 7 (also known as Fast & Furious 7), is a 2015 American action film and the seventh installment in the Fast and the Furious franchise. The previous installment, Fast & Furious 6, grossed over $780 million worldwide after its release in 2013. Furious 7 has nearly doubled its previous record, earning over $1.5 billion worldwide, making it the highest-grossing film in the franchise, according to IMDb, an Amazon.com owned online database. In China, Furious 7 has also made 2.6 billion RMB (approximately 400 million USD), and has created the highest box office record in the history of Chinese film market.
What we have learned from this phenomenon is that the Chinese population has a growing interest towards the automobile industry, and their choice of vehicle is also evolving based on popular culture and western influences. Ten years ago, what the Chinese had considered first when purchasing a car is its aesthetic attractiveness. Today, however, people have turned to pursue vehicles with high performance and state-of-the-art technologies – such as the turbocharger.
A turbocharger is a turbine-driven forced induction device used to boost efficiency of an engine by forcing more air into the engine’s combustion chamber, which in turn creates more power. This technology allows smaller turbocharged engines to achieve the same performance as larger non-turbocharged engines in one acceleration and on demand. For instance, the performance of a 1.8T turbocharger can reach the same energy output of a 2.4L engine with similar fuel consumption. Moreover, a turbocharger can boost an engine’s horsepower without significantly increasing its weight, making it more efficient, compact, environmentally friendly, and a new attractive option for automotive manufacturers and motorists alike.
Although turbocharged engines can be very efficient, they also run at immense speeds, operating under huge pressures and temperatures, which can influence the working life of the auto-engine. To prevent overheating, turbochargers require dedicated supply of oil and water for proper cooling. Moreover, parts of the turbocharger are generally made of heat-resistant alloys, with characteristics such as high thermal stability and resistance to fatigue and erosion. Machining heat-resistant alloys, however, is not an easy ordeal.
Heat-resistant alloys typically contain elements such as iron, titanium, chromium, nickel, vanadium, tungsten and molybdenum, all of which contribute to the materials’ high hardness, high toughness, low specific gravity and high melting point properties. These alloys are approximately 5-20 percent the machinability of S45C carbon steel. Most exhaust gas turbochargers today can reach 600 degrees centigrade or even higher during machining. Short tool life is a common obstacle when machining these durable materials. When machining the shell of the turbocharger, tapping is necessary. Taps can be abraded severely during machining. Under extreme cutting conditions, conventional taps may only produce several holes per tool.
In Tianjin, China, OSG has a customer who manufactures turbochargers. This Chinese manufacturer is one of the top leaders in the turbocharger industry. Their turbocharged engine is manufactured with a special material that contributes to superior performance and long engine life. For confidentiality reasons, the name of the customer and details of their turbocharger material cannot be disclosed. However, what can be shared openly regarding this material is that it has the same property as heat-resistant alloys with hardness above 35 HRC.
The turbocharger shell requires tapping holes that are 12 mm in diameter and 20 mm in depth. Including OSG, four cutting tool manufacturers have initially competed for this application. After a careful evaluation, OSG recommended the NI-SFT spiral tap to the customer. The non-coated NI-SFT is a tap series engineered specifically for heat-resistant alloys. The NI-SFT employed powered metal HSS to enhance wear resistance and avoid chipping in heat-resistant alloys. Moreover, the NI-SFT has adopted a 10-degree low spiral geometry, which encourages high rigidity and effective chip removal.
The trial lasted for a week with repetitive testing. The turbocharger is a very complex piece of machinery. All components within the turbocharger must be precisely coordinated in order to achieve optimal performance. Reliability is a key determinant in this particular trial as heat resistant alloys can be costly, so is scrapping a part. Under identical cutting condition, the competitor manufacturers averaged 380 holes. OSG, on the other hand, was able to produce 1,000 holes. More importantly, OSG was able to demonstrate superior reliability, with the NI-SFT being able to consistently produce approximately 1,000 holes in every trial. With heat-resistant alloys being materials with extremely poor machinability, OSG’s consistent performance was beyond the customer’s expectation. In fact, they were so surprised by the result that it made them shake in excitement. Performance reliability can allow manufacturers to better control and monitor production cost. Choosing the NI-SFT was a no-brainer. After all, who wouldn’t want a tool that can provide satisfactory predictable results every time?
As heat-resistant alloys have become increasingly widespread in industrial manufacturing, OSG has dedicated a tremendous amount of resources in research and development over the years to offer manufactures with innovative cutting tool solutions suitable for their applications with complete confidence. Put our tools into the spindle and you will experience the fast and furious performance of OSG tooling!