Analysis on how to improve the warping deformation of cylinder head and intake and exhaust manifold through heat treatment of super audio frequency induction heating equipment

The cast iron cylinder head and the intake and exhaust manifolds of the agricultural vehicle engine are important parts on the engine. The material is HT150. During production, it is found that before the heat treatment of the super-audio induction heating equipment, due to the thermal stress and mechanical stress during the operation of the engine, plane warping occurs. curved deformation. The flatness error of the warping deformation of the cylinder head is 0.60-0.70mm, and the flatness error of the intake and exhaust manifolds is 0.7-2.0mm, which exceeds the technical standard requirements. If it continues to work, the cylinder gasket will burn out and the engine will leak. In this regard, machining milling or planing planes have been used before, but after machining, it is found that the volume of the cylinder head combustion chamber is uneven, resulting in the disadvantages of idling and unstable operation of the engine, so it is not suitable to use; and the gas manifold has been planed many times. After processing, the thickness of the plane is thinned, the strength is reduced and it cannot be used. Later, after the heat treatment method of the super-audio frequency induction heating equipment, the warping and deformation of the workpiece were manually repaired, and good results were achieved, meeting the above technical requirements for the workpiece.

In the test, the planes of two out-of-tolerance cylinder heads were assembled into one body, and an iron sheet was placed at each end of the plane, with a size of 60mm X 15mm x (0. 6 ~ 0. 7) mm (dimensions according to the warpage of the workpiece size adjustment), and then tighten the bolts to fix the cylinder head. The two pieces of the intake and exhaust pipes are combined and fixed and tightened with 8 bolts. The aging process test shows that after the heat treatment process of super-audio frequency induction heating equipment, the full-length flatness error of the plane warping deformation of the cylinder head is only 0.07-0.20mm, and the full-length flatness error of the plane warping deformation of the intake and exhaust manifolds is 0.25- 0.50mm, fully meet the technical requirements. During the production test, it was found that the cylinder head was kept warm at a temperature lower than 550°C, the intake and exhaust manifolds were kept warm at a temperature lower than 600°C, and the warping and deformation flatness of the workpiece was still out of tolerance, failing to meet the requirements of technical standards. If the cylinder head is kept warm above 600°C, it is less likely to have excessive reverse warpage. The intake and exhaust manifolds are restricted by the mechanical factors of the workpiece structure and are not prone to reverse warping. However, the temperature is too high during heating, which is prone to local distortion and deformation, so it should also be avoided. In addition, after the workpiece is kept warm, it should be cooled slowly with the furnace. Too fast cooling is prone to stress and deformation defects. Usually, the furnace is cooled to 200°C and then air-cooled.

The cast iron cylinder head of the engine and the intake and exhaust manifold parts are treated with super-audio frequency induction heating equipment heat treatment process, which solves the warping and out-of-tolerance defects of the workpiece, meets the technical requirements, and is successfully applied in production.