In the soaking furnace at Pilsen Steel in the Czech Republic, 34CrNiMo6 steel ingots are heated to 1,100°-1,200°C prior to forging.
Pilsen Steel is a Czech manufacturer of steel ingots, ductile- and gray-iron castings, and finished machined forgings for a multiple industrial markets, including power generation and shipbuilding. Two-thirds of the company’s shipments are exported, and have been used in high-profile projects all over the world. For example, Pilsen Steel provided the wheel shaft and 200 metric tons of other castings for the London Eye Ferris wheel. Pilsen Steel also is one of the world’s highest-volume producers of wind turbine shafts, and one of the largest suppliers of large crankshafts for four-stroke diesel engines.
Pilsen does all of its production at one plant, in the city of Pilsen, in the western part of the Czech Republic, where it has steelmaking, metalcasting, forging, round and finish machining operations. Recently the company recognized a problem with material cracking on a batch of 34CrNiMo6 steel ingots during forging.
After casting, the ingots had been quenched in water to 500°-600°C, prior to reheating in a soaking furnace to temperatures of 1,100°-1,200°C. It was unclear whether the cause of the cracks had been the heating or the forging operation, and Pilsen contracted Comtes FHT a.s. to investigate, determine the root cause, and suggest a remedy.
Comtes FHT is a non-profit organization focused on applied research for industrial partners involved in the production of metal products. Its services include fracture-toughness testing, high-temperature testing, fatigue testing, strain measurement, material analysis with electron microscopes, electron backscatter diffraction (EBSD) analysis, and energy dispersive X-ray analysis (EDX) of chemical composition. The organization is experienced at physical testing, material analysis, computer simulation, process design and development, and prototype manufacturing.
Pilsen Steel supplied the ingot and furnace geometries to Comtes FHT as 2D drawings. Comtes researchers reproduced the ingot geometry in desktop CAD software, then created a simple 2D axisymmetric model of a single ingot and the furnace wall. Comtes obtained the material properties for the simulations through experimental tests that included thermal capacity, thermal conductivity, heat expansion coefficient, and phase transformation.