With the development of the global manufacturing industry, especially the continuous emergence of new materials and processes, the improvement of product processing accuracy, and the emergence of high-pressure, high-speed, and high-flow machine tool cooling systems, the unique role of cutting fluid as a cutting medium in the metal processing process cannot be ignored.
With the development of modern machining technology, the metal processing industry has put forward stricter requirements for metal cutting fluids. Due to the diversity of machining processes and the particularity of machining materials, it is difficult to find a foolproof cutting fluid product that can meet all machining requirements. Therefore, the specialization of metal cutting fluids will inevitably become a development trend in the industry. 1. Processing characteristics of cylinder head The cylinder head is a complex box part and a key component in engine components. Its precision requirements are high, the machining process is complex, and the machining quality directly affects the overall performance of the engine. For the manufacturing of engine cylinder heads, although the manufacturing system varies among many automobile manufacturers, there are many similarities in the processing technology and process design used. Among them, the machining of the conical surface of the intake and exhaust valve seat rings and the guide hole is the most critical process in the machining of the cylinder head. The general requirements for machining accuracy are: the coaxiality tolerance of gasoline engines is specified as 0.015-0.025mm; For diesel engines, it is only 0.01-0.015mm. Valve guides and seat rings are usually made of iron based powder metallurgy materials. To ensure the coaxiality tolerance of the valve seat and conduit hole bottom hole, most manufacturers usually use specialized equipment and composite cutting tools for processing. The special tool first spots the conical surface of the valve seat, and after machining the seat ring, the tool moves back about 0.2mm. Then, the tool speed increases and the reamer is pushed at a constant feed rate to process the conduit hole. After the processing of the conduit hole is completed, the special tool returns to its original speed and the reamer automatically returns to its starting position.
2. Characteristic requirements for using cutting fluids The characteristic requirements for the use of cutting fluid during the machining of cylinder head valve seat rings and guide holes can be summarized as follows: 2.1 Cutting fluid must have high strength composite lubrication ability In specific production practices, we have found that the machining of conduit holes and valve seat rings requires different lubrication characteristics of the cutting fluid. Machining conduit holes requires high strength extreme pressure lubrication of the cutting fluid, while machining valve seat rings puts forward abnormally high requirements for boundary lubrication of the cutting fluid. The Gaofei series has developed cutting fluid products with composite lubricating additives in response to this situation, and has demonstrated excellent machining characteristics in on-site use. 2.2 The cutting fluid must be able to work in the cooling pressure system above 6MPa without foam problem.
Due to the environmental requirements of the valve guide hole and seat ring, the materials in these two parts must have both wear and high temperature resistance characteristics. In order to meet the cutting environment requirements when processing this material, the cooling system must be able to effectively deliver the cutting fluid to the cutting area and effectively remove iron chips from the machining area to ensure sufficient cooling during the cutting process.
When machining these two parts, high pressure (above 6MPa) internal cooling and large flow cutting fluid supply mode is mostly used, which requires that the selected cutting fluid must meet the characteristic requirements of low foam. For example, a large number of foam generated in the use of cutting fluid will greatly reduce the use effect of cutting fluid, resulting in the decline of tool durability and workpiece surface quality.
3. Suggestions for the use of cutting fluid
3.1 Lotion type cutting fluid shall be used, and the mineral oil content of concentrated fluid shall be more than 50%
In addition to having composite extreme pressure lubrication capability, the cutting fluid must also have sufficiently high oiliness to provide effective mechanical lubrication capability for cutting.
3.2 The concentration of cutting fluid should be above 15%
Although different cutting fluids have different requirements for concentration during use due to their different formulations, the cutting fluid must have the ability to provide high-strength extreme pressure lubrication, boundary lubrication, and mechanical lubrication according to the material characteristics of the valve guide and seat ring during cutting. Properly increasing the concentration of the cutting fluid can effectively extend the service life of the tool and the surface processing quality of the workpiece, The increased consumption cost caused by increasing the concentration of cutting fluid is insignificant for enterprises.
The four major functions of cutting fluid, namely lubrication, cooling, cleaning, and rust prevention, are widely known. They are unified, but at the same time, they are opposite. How to achieve the best balance point is a goal that many manufacturers are concerned about. Each cutting fluid manufacturer's products have their own focus and specificity. As the most critical machining process for valve seat rings and guide holes in cylinder head machining, the selection of cutting fluid is particularly important.
