Stainless steel processing difficulties analysis and solutions [comprehensive analysis

As the content from the network, by the “Shenzhen Machinery Exhibition (110,000 square metres, more than 1,100 exhibitors, more than 100,000 visitors) collected and collated, the stainless steel machining difficulties in a comprehensive analysis and solutions [comprehensive analysis]! More cnc machining centres, as well as turning, milling, grinding and drilling machines, as well as wire cutting, CNC cutting tools, industrial robots, non-standard automation, digital unmanned factories, precision measurements, CNC systems, 3D printing, laser cutting, sheet metal stamping and bending, precision parts processing and other aspects of the show, in Shenzhen Machinery Exhibition. [Abstract] new finished products continue to appear, for the parts material gives a more stringent conditions, the required materials sometimes have to meet the high hardness, and high wear resistance, as well as high toughness and other special conditions, accordingly produced a number of difficult to process the material, to the processing process puts forward more stringent conditions. Stainless steel as the object of such difficult-to-machine materials in this paper, combined with the actual problems I encountered during the processing of stainless steel processing difficulties to be analysed, but also put forward practical and effective solutions. [Keywords] stainless steel; cutting; processing methods 1.Introduction and high quality carbon structural steel compared to it, stainless steel materials added Cr, Ni, N, Nb, Mo and other alloying elements, the addition of these alloying elements, not only to enhance the corrosion resistance of the steel, for the mechanical properties of stainless steel also has a certain impact. Like martensitic stainless steel 4Cr13, which is compared with 45 carbon steel, the two have the same carbon content, however, its relative machinability is only 45 steel 58%; austenitic stainless steel relative machinability, only 40%, and austenitic - ferrite duplex stainless steel toughness is very high, and its cutting is even worse. In the actual processing, the stainless steel cutting, often accompanied by the occurrence of broken knife phenomenon, but also accompanied by the emergence of sticky knife phenomenon. In view of the stainless steel in cutting at the time of plastic deformation amplitude, so that the generated chips are difficult to break, easy to bond, which leads to the cutting process in the work hardening condition is quite serious, and with each cutter will be for the next cutting to form a hardened layer, after layers of accumulation, stainless steel in the cutting process of hardness continues to increase, and the required cutting force followed by a rise. The emergence of the hardening layer and the cutting force will lead to increased friction between the tool and the workpiece, the cutting temperature also rises. Moreover, the coefficient of thermal conductivity of stainless steel is relatively small, poor heat dissipation conditions, a large number of cutting heat convergence between the tool and the workpiece, making the machined surface becomes bad, the quality of the machined surface has a serious impact. Moreover, once the cutting temperature rises, it will make the tool suffer more serious wear, resulting in the formation of crescent pits on the front face of the tool, the cutting edge of the chip, which in turn affects the surface quality of the workpiece, making the work efficiency is reduced, and the production cost has increased.3. The way to improve the quality of stainless steel machining. From the above it can be seen that the processing of stainless steel is more difficult, easy to produce a hardened layer during cutting, but also easy to break the knife phenomenon; the resulting chips are not easy to break off, resulting in a sticky knife situation, which will make the tool wear increased. For these cutting characteristics of stainless steel, in connection with the actual production situation, we start from the tool material, cutting parameters and cooling method of the three aspects, looking for ways to improve the quality of stainless steel machining.3.1 Selection of tool material, select the appropriate tool is the foundation of the processing of high-quality parts. Tool quality is not good, will not be able to process the standard parts; if the selection of too good quality tools, although the surface quality of the parts can meet the demand, but it is easy to form a waste, resulting in increased production costs. Stainless steel in the cutting heat dissipation conditions are not good, produce work hardening layer, easy to stick knife and other characteristics of the combination of the selection of cutting tool materials should meet the heat-resistant performance is good, wear-resistant performance is quite high, and stainless steel and the affinity effect of the characteristics of the small. 3.1.1 high-speed steel, high-speed steel is a kind of alloying elements such as W, Mo, Cr, V, Go and other high-alloyed tool steel, which has a better process performance, its strength and toughness with good, its Strength and toughness with good, its resistance to shock and vibration ability is relatively strong, in the case of high speed cutting produces high heat (about 500 ℃) is still able to maintain a high hardness (HRC is still above 60), high-speed steel red hardness is good, suitable for use in the production of milling cutters, turning tools, such as milling cutter, to meet the stainless steel cutting hardened layer and poor heat dissipation and other cutting environments. It is very typical of high-speed steel cutting tools, since its introduction in 1906, has been made into a large number of various types of tools to meet the needs of cutting. However, with the various types of machined materials continue to enhance the mechanical properties, the tool has been unable to meet the processing requirements of difficult-to-machine materials. High-performance cobalt high-speed steel appeared at the right time. Compared with ordinary high-speed steel, cobalt high-speed steel has more excellent wear resistance, red hardness and the use of reliability, suitable for high excision rate processing and intermittent cutting, commonly used grades such as. 3.1.2 Cemented Carbide Steel, Cemented Carbide is mainly composed of high hardness refractory metal carbide (WC, TiC) micron-sized powders, it is to cobalt or nickel, molybdenum as a binder, is in the vacuum furnace or hydrogen It is a powder metallurgical product sintered in a vacuum furnace or hydrogen reduction furnace. Cemented Carbide has excellent properties regarding strength and toughness, heat resistance, wear resistance, corrosion resistance and high hardness. It can remain basically unchanged at a temperature of 500°C, and still has high hardness at 1000°C, making it suitable for cutting stainless steel, heat-resistant steel and other difficult-to-machine materials. Common cemented carbide is mainly divided into three categories, one is YG class, that is, tungsten-cobalt cemented carbide, one is YT class, that is, tungsten-titanium-cobalt, and one is YW class, that is, tungsten-titanium-tantalum (niobium) class, these three kinds of alloys, there are differences in their compositions, and the use is also a great difference, in which the YG class of cemented carbide, because of the good toughness, thermal conductivity is also better, so it can be selected! 3.2 Cutting stainless steel tool geometry parameters selection, 1) front angle γo: stainless steel has high strength, good toughness, cutting chips are not easy to be cut away from the characteristics of the knife in the case to ensure that the knife has sufficient strength, should be selected with a larger front angle, in this way, not only can reduce the plastic deformation of the object of processing, but also reduce the cutting temperature and cutting force, but also reduce the hardened layer. 2) the hardened layer. (2) the back angle αo: increase the back angle will reduce the friction between the machining surface and the back face, but the cutting edge of the heat dissipation ability and strength will also be reduced. The size of the back angle depends on the cutting thickness, cutting thickness is large, it is appropriate to choose a smaller back angle. 3) the main deflection angle kr, vice deflection angle k′r, the main deflection angle kr to increase the working length of the cutting edge, which is conducive to heat dissipation, but in the cutting will make the radial force increase, which is easy to produce vibration, usually take the value of kr for the 50 ° ~ 90 °, if the machine tool rigidity is not enough, then it can be appropriately increased. Sub-deviation angle is often taken k′r = 9 ° ~ 15 °. (4) edge tilt angle λs, in order to increase the strength of the tip of the knife, the edge tilt angle is usually taken as λs = 7 ° ~ -3 °. 3.3 Cutting fluid and cold to go to the way to choose, in view of the stainless steel cutting and processing of poor, so the cutting fluid cooling, lubrication, infiltration, as well as the cleaning performance has a higher demand, the commonly used cutting fluid contains the following categories: (1) emulsified fluid, which is the more common cooling (1) emulsion, which is the more common cooling method, with good cooling, cleaning and lubricating properties, usually used for stainless steel rough turning; (2) sulfide oil, during cutting in the metal surface to form a high melting point sulfide, and in high temperature conditions are not easy to be destroyed, with good lubrication, while having a certain cooling effect, generally used for drilling, reaming, and tapping. (3) machine oil, spindle oil, and other mineral oils show such characteristics. It has good lubricating properties, but the cooling performance and permeability is relatively poor, in this case for external fine turning. During the cutting process, it is necessary to align the cutting fluid nozzles with the cutting zone, or to give priority to high-pressure cooling, as well as spray cooling.