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GB/T23339-2009 "Technical Conditions for Crankshaft of Internal Combustion Engine" has two aspects compared with the original JB/T6727-2000 "Technical Conditions for Crankshaft of Internal Combustion Engine". First, in terms of materials, the regulations for the use of non-tempered steel were added for the first time. It is recommended to use F40MnV non-tempered steel or other similar non-tempered steel grades specified in GB/T15712 "non-tempered mechanical structural steel", which promotes non-tempered steel, a green, energy-efficient, environmentally friendly green steel. The application on the crankshaft of internal combustion engines will play a large role. Non-tempered steel is a new type of steel that was introduced in the early 1970s and has been in existence for less than 40 years since its birth. It is based on the addition of vanadium, titanium and niobium microalloying elements to the medium carbon manganese steel, so that it dissolves in the austenite during heating, because the solid solubility of vanadium, titanium and niobium in austenite With cooling reduced, the microalloying elements vanadium, titanium, and niobium will precipitate in the first precipitated ferrite and pearlite in the form of fine carbides and nitrides. These precipitates maintain a coherent relationship with the parent phase and strengthen the steel. The mechanical properties of such steels in the hot rolled state, the forged state or the normalized state are close to or reach the level of mechanical properties of the general quenched and tempered state. Therefore, the use of non-tempered steel to manufacture mechanical parts can omit the quenching and tempering process, which shortens the production cycle and saves energy. Generally, energy consumption and manufacturing costs can be reduced by 25% to 38%. At present, there are more and more non-tempered steel forgings for hot forging. For example, non-tempered steel crankshafts, connecting rods, camshafts and other internal combustion engine parts have been used in automotive and other industries instead of quenched and tempered steel. The current national standard for non-tempered steel is GB/T15712-2008 "non-tempered mechanical structural steel".
Second, in terms of heat treatment, 1) the recommended forged steel crankshaft is rounded and quenched, and the ductile iron crankshaft is nitrided or rounded and rolled to enhance the fatigue strength of the crankshaft. At present, some forged steel crankshafts are treated with nitriding, which is not worth promoting. 2) The provisions on the upper limit of the hardness of the forged steel and the quenching and tempering treatment of the forged steel crankshaft are improved. The hardness of the normalized crankshaft is changed from 163HBW~241HBW to 163HBW~277HBW; the hardness of the crankshaft after quenching and tempering is adjusted from 207HBW~302HBW to 207HBW~320HBW. 3) Increased hardness requirements for non-quenched and tempered steel crankshafts. After the non-tempered steel crankshaft forgings are air-cooled, the hardness at the specified position of the pattern should be in the range of 207HBW~277HBW. 4) Unification of the depth of the hardened layer of the forged steel crankshaft and ductile iron crankshaft. The depth of the quench hardened layer of the crankshaft surface of both materials is uniformly modified to 1.0mm~4.5mm.
GB/T23340-2009 "Technical Conditions of Connecting Rods for Internal Combustion Engines" Compared with the original JB/T6721-1993 "Technical Conditions for Connecting Rods of Internal Combustion Engines", the biggest change is to clearly give the mechanical performance index of connecting rods, which is not the standard of the original machinery industry. . For the connecting rod, the mechanical performance index is an important technical requirement. At present, most of the internal combustion engine connecting rod product drawings have only hardness requirements, and there are no other mechanical performance requirements. The main reason is that China's original connecting rod machinery industry standards lack this provision. For the first time, the new national standard stipulates the mechanical performance requirements of the connecting rod, which will have great significance for ensuring the intrinsic quality of the connecting rod. The mechanical performance indicators specified in the new national standard are shown in the table. In addition, the national standard for connecting rods of internal combustion engines no longer specifies the hardness of the connecting rod after quenching and tempering, and the hardness value of the connecting rod is uniformly specified. Regardless of the material of the connecting rod, the hardness of the link body and the connecting rod cover after quenching and tempering should be in the range of 207HBW~320HBW.
With the development of the economy, internal combustion engine machinery has been more and more widely developed and used. The release of the national standard for crankshafts and connecting rods of internal combustion engines indicates that the state attaches great importance to the quality of crankshafts and connecting rods of internal combustion engines, which is of great significance for ensuring the quality of crankshafts and connecting rods and ensuring the safe operation of internal combustion engine machinery. The newly released two national standards are more comprehensive in technical content, more organized, and more in line with current relevant standards. Companies producing crankshafts and connecting rod components for internal combustion engines should actively implement the two new national standards to further improve the quality of internal combustion engine crankshafts and connecting rods.
Cylinder and connecting rod product standards for internal combustion engines are upgraded to national standards
Crankshafts and connecting rods are key components on automotive engines. Previously, the internal combustion engine crankshaft and connecting rod product standards were all mechanical industry standards. In order to ensure the quality of crankshaft and connecting rod of internal combustion engine, in 2009, China first upgraded the internal combustion engine crankshaft and connecting rod standard to national standard. The standard number and name are GB/T23339-2009 "Technical conditions for internal combustion engine crankshaft" and GB/T23340-2009 Technical conditions for connecting rods of internal combustion engines. The two national standards are managed by the National Internal Combustion Engine Standardization Technical Committee and are applicable to crankshafts and connecting rods of reciprocating internal combustion engines with a cylinder diameter of not more than 200 mm. They were issued by the National Standardization Administration Committee on March 19, 2009, and in 2009. Formally implemented on the 1st of the month. After the implementation of the original machinery industry standard JB/T6727-2000 "Engineering conditions of internal combustion engine crankshaft" and JB/T6721-1993 "Technical conditions for connecting rods of internal combustion engines" will be automatically abolished.