In the process of machining stainless steel round pipes, cutting is a process worth noting. If you are not careful, some problems will easily occur. For example, some irregular metal formations, adhesions, etc. Surface roughness grades are reduced due to objects or nicks. So, what are the reasons for the uneven surface of stainless steel round pipe cutting?
Since the plastic flow of the chips and the external friction between the tool and the chip exceed the internal friction during the cutting process, under the action of the huge pressure between the tool and the chip, cold welding occurs between the cutting bottom layer and the front of the tool, thereby forming a built-up edge .
The influence of the built-up edge on the surface roughness of the stainless steel round tube is as follows:
- It can describe longitudinal grooves;
- It will also adhere to the machined surface when it is broken and fallen off.
This is because when the built-up edge is in the growth stage, it is firmly adhered to the rake face, and therefore has a greater chance of scratching the longitudinal groove on the machined surface than it does on the machined surface. When a built-up tumor is at its maximum extent and in the regression stage, it is unstable. At this time, although the grooves are sometimes depicted, they are more attached to the processed surface.
A scaly burr is a scaly burr on a machined surface. The generation of flakes is due to the bonding phenomenon that occurs when the chips and the rake face are severely rubbed during the custom machining china process. Under the extrusion action of the accumulated bonding layer, the plastic deformation of the metal layer is strengthened, resulting in the appearance of the machined surface in front of the cutting edge. crack. When the cutting force exceeds the bonding force, the chips flow out and are cut off, causing the crack layer to remain on the surface of the stainless steel tube that has been machined to form scales. It seriously affects the quality of the machined surface, and usually reduces the surface roughness of the 304 stainless steel pipe by 2 to 4 grades.
If there is vibration during the cutting process, vibration marks will appear on the machined surface, and the surface roughness will increase significantly. Vibration is caused by excessive radial cutting forces or low stiffness of the workpiece system. Vibration during cutting can create vibration marks on the machined surface. The vibration mode is longitudinal, lateral or oblique distribution. The level of the vibration waveform is related to the vibration amplitude, mode shape density and vibration frequency. Vibration not only has a great impact on tool wear, but also deteriorates the surface quality of stainless steel round tubes.
In addition to the above factors, the reasons for the rough and uneven surface also include: extrusion and friction marks caused by wear behind the tool; blade defects are reflected on the machined surface, and are scratched and scratched by chips.
In the process of machining 304 stainless steel pipe, due to the geometry of the tool, geometric parameters, the feed movement of the cutting edge and the roughness of the cutting edge itself, the material layer on the machined surface is not completely removed, leaving residues on the machined surface. area, the height of the residual area constitutes the surface roughness.
The above is the reason why the surface of the stainless steel round tube is not smooth during machining, and the reasons for the surface roughness during cutting can be summarized into three aspects:
- One is the residual area left by the blade on the surface of the workpiece during the cutting process;
- The second is the influence of plastic deformation and the formation of built-up edge and scale spine in the cnc machining process;
- The third is the slight vibration of the relative position of the blade and the workpiece during the cutting process.
The first two reasons are affected by the geometric parameters of the tool, cutting amount, workpiece material, tool material and cooling and lubrication, and the latter reason is related to the vibration of the process system.