Testing of Castings and Forgings

Castings and forgings are primarily used in the automotive industry and in aerospace and power plant construction. Casting technology allows complex parts to be manufactured cost effectively, with an ever-increasing use of light metal castings to reduce weight, especially in engine manufacture. For extreme demands regarding strength, pressure or impact loading, forged components are used, as are crankshafts and connecting rods in engines, and generator and turbine shafts in power plants.

Hardness Testing

The hardness value is an important characteristic when monitoring the manufacturing process for cast and forged components. The high-load Brinell method is often used on components, the large indentations enabling a stable average value for the metallographic constituents to be obtained. The hardness of metallographic constituents is determined on metallographic specimens through Vickers micro-hardness testing. Zwick’s operator-friendly Brinell hardness testing machines with automatic indentation measurement up to load level of 3000 (29,000 N) are complemented by a comprehensive micro Vickers instrument portfolio, including fully automated systems.
Lens turret on hardness tester to Vickers ZHV30/zwickiLine

Tensile Testing

Cast and forged components are produced in a way that the smallest degree of further processing is needed to make them fulfill their intended purpose.   For tensile tests, this means either removing specimens from specified locations or using the component as a whole to determine tensile strength. Testing the whole component requires high test loads and component-specific gripping arrangements and fastenings, while component geometries often result in the production of specimens with small final dimensions. For small round specimens, Zwick provides special specimen grips which are easy to handle and allow the use of automatic extensometers; complete components are tested with the help of a comprehensive accessory and option package.

Fatigue Tests

In practice, where castings and forgings are concerned, reliable estimation of durability is of particular importance. This requires single specimens and, importantly, entire components such as forged connecting rods, to be tested intensively under cyclic loading. These fatigue tests are performed in resonance testing machines for example, and components are stressed with cyclic loads up to 600 kN at frequencies up to 285 Hz. Zwick’s range of highly efficient, cost-effective resonance testing machines is now also backed by a greatly expanded servo-hydraulic testing machine portfolio.

Temperature-controlled progressive load tests on cast iron materials

To characterize the specific properties of gray cast iron (cast iron containing lamellar graphite) the Austrian Foundry Research Institute (ÖGI) is carrying out progressive load tests at both room temperature and elevated temperatures. Progressive tensile tests using a Zwick 100kN AllroundLIne testing machine are designed to determine the temperature dependence of Young's modulus and of the static E0 modulus of gray cast iron.