Method for improving the quality of stainless steel processing

Compared with high-quality carbon structural steel, stainless steel materials are added with alloying elements such as Cr, Ni, N, Nb, and Mo. The increase of these alloying elements not only improves the corrosion resistance of the steel, but also has an effect on the mechanical properties of the stainless steel. For example, martensitic stainless steel 4Cr13 has the same carbon content compared with 45 medium carbon steel, but the relative machinability is only 58% of 45 steel; austenitic stainless 1Cr18Ni9Ti is only 40%, and austenite-iron The metamorphic duplex stainless steel has high toughness and poor machinability.
Analysis of difficult points in stainless steel material cutting:

In actual machining, cutting stainless steel is often accompanied by the occurrence of broken and sticky knives. Due to the large plastic deformation of stainless steel during cutting, the generated chips are not easy to be broken and easy to bond, resulting in serious work hardening during the cutting process. Each time the cutting process produces a hardened layer for the next cutting, and the layers are accumulated, and the stainless steel is in the cutting process. The hardness in the middle is getting larger and larger, and the required cutting force is also increased.

The generation of the work hardened layer and the increase of the cutting force inevitably lead to an increase in the friction between the tool and the workpiece, and the cutting temperature also increases. Moreover, stainless steel has a small thermal conductivity and poor heat dissipation conditions, and a large amount of cutting heat concentrates between the tool and the workpiece, which deteriorates the processed surface and seriously affects the quality of the processed surface. Moreover, the increase of the cutting temperature will aggravate the tool wear, causing the crescent of the rake face of the tool, and the cutting edge will have a gap, thereby affecting the surface quality of the workpiece, reducing the work efficiency and increasing the production cost.

CNC-车削件类型-7

Ways to improve the quality of stainless steel processing:

It can be seen from the above that the processing of stainless steel is difficult, and the hardened layer is easily generated during cutting, and the knife is easily broken; the generated chips are not easily broken, resulting in sticking of the knife, which will aggravate the wear of the tool. Processing all kinds of high-quality stainless steel workpieces to identify Titanium machinery, for the cutting characteristics of stainless steel, combined with the actual production, we start from the three aspects of tool materials, cutting parameters and cooling methods, to find ways to improve the quality of stainless steel processing.

First, the choice of tool materials

Choosing the right tool is the basis for producing high quality parts. The tool is too bad to process qualified parts. If the tool is too good, it can meet the surface quality requirements of the part, but it is easy to waste and increase the production cost. In combination with stainless steel cutting, poor heat dissipation conditions, work hardened layer, easy to stick knife, etc., the selected tool material should meet the characteristics of good heat resistance, high wear resistance and small affinity with stainless steel.

1, high speed steel

High-speed steel is a high-alloy tool steel with alloy elements such as W, Mo, Cr, V, Go, etc. It has good process performance, good strength and toughness, and strong resistance to shock and vibration. It can maintain high hardness (HRC is still above 60) under high heat generated by high-speed cutting (HRC is still above 60). High-speed steel has good red hardness and is suitable for milling cutters such as milling cutters and turning tools. It can meet the requirements of stainless steel cutting. Cutting environment such as hardened layer and poor heat dissipation.

W18Cr4V is the most typical high speed steel tool. Since its birth in 1906, it has been widely used in various tools to meet the needs of cutting. However, with the continuous improvement of the mechanical properties of various materials being processed, W18Cr4V tools can no longer meet the processing requirements of difficult materials. High-performance cobalt high-speed steel is born from time to time. Compared with ordinary high-speed steel, cobalt high-speed steel has better wear resistance, red hardness and reliability of use. It is suitable for high resection rate processing and interrupted cutting. Commonly used grades are W12Cr4V5Co5.

2, hard alloy steel

Cemented carbide is a powder metallurgy which is made of high-hardness refractory metal carbide (WC, TiC) micron-sized powder and sintered with cobalt or nickel or molybdenum in a vacuum furnace or a hydrogen reduction furnace. product. Cemented carbide has a series of excellent properties such as good strength and toughness, heat resistance, wear resistance, corrosion resistance and high hardness. It is also basically unchanged at a temperature of 500 ° C, and still has a high hardness at 1000 ° C, and is suitable for cutting of difficult-to-machine materials such as stainless steel and heat-resistant steel. Common hard alloys are mainly divided into three categories: YG (tungsten-cobalt-based cemented carbide), YT-based (tungsten-titanium-cobalt-based), YW-based (tungsten-titanium-tantalum (铌)), which have different compositions. The use is also very different. Among them, YG type hard alloys have good toughness and good thermal conductivity, and a large rake angle can be selected, which is suitable for cutting of stainless steel.
Second, the choice of cutting geometric parameters of stainless steel tools

The rake angle γo: combined with the characteristics of high strength, good toughness, and difficult to be cut off during cutting. Under the premise of ensuring sufficient strength of the knife, a large rake angle should be selected, which can reduce the plastic deformation of the machined object. It also reduces the cutting temperature and cutting force while reducing the generation of hardened layers.

Back angle αo: Increasing the back angle will reduce the friction between the machined surface and the flank, but the heat dissipation capability and strength of the cutting edge will also decrease. The size of the back angle depends on the cutting thickness. When the cutting thickness is large, a smaller back angle should be selected.

The main declination angle kr, the declination angle k'r, and the main declination angle kr can increase the working length of the blade, which is beneficial to heat dissipation, but increases the radial force during cutting and is prone to vibration. The kr value is often 50. °~90°, if the rigidity of the machine is insufficient, it can be increased appropriately. The secondary declination is usually taken as k'r = 9° to 15°.

Blade inclination angle λs: In order to increase the tip strength, the blade inclination angle is generally λs = 7 ° ~ -3 °.
Third, the choice of cutting fluid and cold going

Due to the poor machinability of stainless steel, there are higher requirements for the cooling, lubrication, penetration and cleaning performance of the cutting fluid. The commonly used cutting fluids have the following types:

Emulsion: It is a common cooling method with good cooling, cleaning and lubrication properties. It is often used in stainless steel roughing.

Sulfurized oil: It can form high melting point sulfide on the metal surface during cutting, and it is not easy to break at high temperature. It has good lubricating effect and has certain cooling effect. It is generally used for drilling, reaming and tapping.

Mineral oil such as engine oil and spindle oil: It has good lubricating performance, but has poor cooling and permeability, and is suitable for outer round finishing vehicles.

The cutting fluid nozzle should be aligned with the cutting zone during the cutting process, or preferably by high pressure cooling, spray cooling or the like.

In summary, although the stainless steel has poor machinability, it has the disadvantages of severe work hardening, large cutting force, low thermal conductivity, easy sticking, easy to wear tools, etc., but as long as a suitable machining method is found, the appropriate tool, cutting method and The amount of cutting, choose the right coolant, diligent thinking during work, stainless steel and other difficult materials will also meet the "blade" solution.

We specialize in CNC turning, CNC milling, CNC grinding services for over 15 years! Our factory is ISO9001 certified and the main markets are USA, Italy, Japan, Korea, Russia and Belgium.

If you have any requirements, you can contact us and we will contact you as soon as possible!

Anebon Metal Products Co., Ltd.
Skype: jsaonzeng
Mobile: + 86-13509836707
Phone: + 86-769-89802722
Email: info@anebon.com

 


Anebon Metal Products Limited can provide CNC machining, die casting, sheet metal machining services, please feel free to contact us.
Tel: +86-769-89802722 Email: info@anebon.com Website : www.anebon.com


Post time: Aug-04-2019
WhatsApp Online Chat !