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Engine Parts Heat Treatment
Oct 16, 2017

Engine Parts Heat Treatment
At present, in the production of Engine Parts, the largest carbon steel Engine Parts single weight of 180t, the maximum heat treatment furnace size of 13mXllmX5.5m. For the high standards of performance requirements of different shipyards and classification societies, heat treatment is carried out in the traditional technology using normalizing and tempering, but for high strength (tensile strength above 480Mpa) and high impact toughness (0 ° C 27J , And even the user requirements to achieve 0 ° C 55J above) requirements, compliance is difficult, and the performance is not stable enough. The traditional heat treatment process is shown in Fig. This kind of heat treatment process is not suitable for large-scale Engine Parts, especially marine carbon and manganese steel castings, the reason, nothing more than the following three (1) due to large Engine Parts thick wall thickness, need a long time insulation, will lead to Grain growth; (2) due to the normalizing cooling rate is insufficient, prone to grain of the original position to retain the show. (3) when the need to 480W level of products but also to ensure that the chemical composition of low-carbon, the traditional process requires a long time to temper the tempering, the performance of the performance of the product is not stable, Processing, in which case it is more prone to lower strength and thus fail to meet the standard requirements. In the use of traditional technology, to meet the high strength requirements, the impact toughness success rate of only 30%. Therefore, the use of appropriate heat treatment process, the carbon-manganese steel Engine Parts both to meet the high strength, but also to meet the high impact toughness, especially low-temperature impact toughness is the industry in the Engine Parts manufacturing a bottleneck. The development of a new type of marine carbon-manganese steel Engine Parts heat treatment process, breaking the use of large-scale heat treatment furnace, handling large quantities, large tonnage of marine carbon steel steel casting heat treatment bottlenecks, the industry is an urgent need to solve one of the key issues.
The invention has wide applicability, and can cover the large wall thickness of the most of the carbon and manganese steel Engine Parts, which is advantageous for the furnace of the large heat treatment furnace, which can improve the utilization efficiency and the production efficiency of the equipment. 2. The invention can meet the requirements of the existing ship regulations for the impact toughness at different temperatures while ensuring high strength. 3, can save a lot of heat treatment time and reduce the heat treatment costs (1) in the first normalizing, cooling to 700 ° C can be a second normalizing, from 700 ° C and then heated to 830 ° C temperature difference At 130 ° C, less than the traditional process from 200 ° C to 600 ° C 400 ° C temperature difference, the heating rate is roughly the same circumstances can save a lot of heating time. (2) The second normalizing and holding time is calculated according to the wall thickness of 50mm / h, and the tempering time of the traditional process is calculated according to the wall thickness of 25mm / h, which can save nearly 50% of the holding time. (3) after the second normalizing the cooling, for the furnace down to 600 V can be baked, about 4 hours, while the traditional process of tempering furnace after the cold time of 10 hours, can save 6 hours. 4. The process of the invention is quite stable, is advantageous for mass production, the success rate is very high, reduces the cost of repeated heat treatment and reduces the high cost of ship inspection.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A heat treatment process for a marine carbon-manganese steel Engine Parts shown in Figure 1 is carried out according to the maximum wall thickness of 25 mm / h of the Engine Parts to complete the austenitization of the organization, , Then the first normalizing bake blowing cooling, reduced to 700 ° C in less than one hour, and then no higher than 75 ° C / h heating rate heating to 8300C 20 ° C, 816 hours insulation time, holding time According to Engine Parts maximum wall thickness 50mm / h calculation, and then in the furnace naturally cooled to 600 ° C below, can be baked, into the indoor cooling to room temperature, complete the heat treatment process. Large Engine Parts riser diameter mostly in more than 600mm, the maximum riser diameter of 2. 9m. Thickness of the carbon steel Engine Parts Asustrated tissue segregation serious, columnar crystal structure thick. Large-scale heat treatment furnace furnace size 13mX IlmX 5. 5m, handle such a large Engine Parts its heating rate can not be higher than 75. C / h, if the temperature is too fast, the stress caused by the temperature difference will expand the defects in the Engine Parts, in particular, will expand the crack. The first normalizing, the need for 920 ° C insulation enough time to make the organization completely austenitized, to eliminate the as-cast dendritic grains, so that the alloy composition is uniform, is to ensure the mechanical properties of the prerequisite. The first normalizing cooling temperature is reduced to 700 ° C when the purpose of the first normalizing has been reached, the need for immediate second normalizing. The purpose of this is to further refine the grain while saving a lot of energy. Because the stage of maximum energy consumption during the entire heat treatment process is the warming stage, this process uses a high starting point temperature to heat up, thus saving a lot of energy. The second normalizing can further refine the grain and treat the material into a sorbite state.