1 year ago

MDA Technologies 2/2014

MDA Technologies 2/2014

Machine elements 01 The

Machine elements 01 The heating capacity of the furnace of 2060 kW could supply enough heat for 300 family homes 02 During the carburizing process material samples are brought into the furnace to control the atmosphere not be hardened, will be coated with a carbon stop off paint. In the protected areas the carbon cannot penetrate. Thus during the subsequence carburizing process these areas are excluded from the hardening process and remain soft . The next step is charging the components on hardening racks whereby the parts are moved to the furnace using a crane system, and then heated... now the carburizing begins. During this time a specific protective carbon gas atmosphere is set. The carbon diffuses into the surface layers of the component with the exception of the previously protected surfaces. Zaim Alili, Director of the Reese Quality Management, says: “An online — diffusion computer controls continuously the exact gas composition in dependence on the material and the alloying elements and determines the required time and calculates the corresponding C-level-history.” Not only the gas composition, but also the gas distribution within the furnace is a which is characterized by a high hardness. The quenching tank contains 320 000 l of a special hardening oil. An extremely powerful cooling system with plate heat exchangers ensured that the temperature of the hardening oil only rose only slightly from above 40 °C to just over 50 °C. The oil also flows continuously through a filter system that permanently filters out contaminants. Every few months, the hardening oil is being analyzed at the manufacturer and postdosed with additives to retain its typical properties. The wheel remains in the oil bath for about 6 to 8 hours before it will be moved out of the oil into a cleaning passage and then again into another annealing furnace. At around 170 °C it remains there for an additional 16 hours to reduce internal stresses which have arisen during the martensitic transformation. More treatment steps such as shot blasting and preservation can be made according to customer‘s request. The USA - made gear wheel was fit for the shipkey factor, to allow the components to uniformly enrich with carbon. The same applies to the temperature which, according to Mr. Alili, varies at each point in the furnace within a tolerance range of ±5 °C. For extra control the employees take carbon shim samples at regular intervals samples . These samples are metal strips which spend 20 minutes in the oven atmosphere absorbing the carbon from the atmosphere during the carburizing process. Then the strips are burned to measure the previously absorbed carbon content. The United States spur wheel lingered around 150 hours at 930 ˚C — the equivalent of more than six days in the furnace, to achieve the desired diffusion depth. Finally, it was it brought to the appropriate hardening (austenitizing) temperature for the material of 820 °C. After lifting the furnace lid, the crane transported wheel next-door into the oil bath for quenching. Due to the drop in temperature in carbon enriched steel, a martensitic structure was created 24 MDA Technologies 2/2014

Machine elements 03 The 21 t gear from the USA stayed in the furnace for the enrichment of the boundary layer with carbon for over six days 04 In the quenching tank of 320,000 liters special hardening oil the enriched surface layer gets its final hardness ment without additional treatment steps. A metallurgical sample of the same material as the workpiece went along through all hardening processes to give precise informations about the reached the degree of hardness at the end of the process. The parameters required by the customer in any case have been achieved in full. New Dimensions in Engineering “We create more freedom for designers. That causes an innovative impact on future constructions.” The possibilities of the new hardening investment attracts not only new customers from around the world to the company in Bochum . “We create more freedom for the designers. In many areas of the machinery and plant construction business” says Gerhard Reese “we have to deal with dimensions ever larger, such as in steelmaking, rolling mills, energy plants, extraction of mineral resources, offshore engineering, shipbuilding and wind power. 05 Managing Director Gerhard Reese invested a total of around 23 million Euros in Europe‘s largest endothermic protection gas hardening system Because now the case hardening of large gears and other system components in this order of magnitude is possible, this effects innovation on all types of constructions. “This investment in the the heat treating plant opens up new possibilities to the entire machine building industry, because the previous possibilities of a safe and reproducible heat treatment technology were brought forward a big step. The larger — scope for action has a direct effect on — the machines of the future. Photos: Holger Seybold About Company name: Härterei Reese Headquarters: Bochum, Germany Employees: approx. 280 Services: Case Hardening, Surface Hardening, Vacuum Hardening, quenching, tempering, nitriding, annealing, straightening, Surface Treatment MDA Technologies 2/2014 25


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