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Precautions for processing austenitic large diameter stainless steel pipe

In order to achieve satisfactory quality in the machining of large diameter stainless steel pipes, the turning tools must have suitable rake angles and back angles. Generally, the tool for automatic lathes should be installed in a position suitable for straight cutting, while the turning tool differs in that the position is mounted for radial cutting. The cutting angle, longitudinal rake angle, lateral rake angle, sub-rear angle and lateral relief angle of the single-edged knife must be sharpened on the tool because the cutting force of the large-diameter stainless steel tube occurs in these places. Ordinary integral turning tools, symmetrical turning turning tools and automatic turning machines are straight-angle turning tools. Because they are mainly used for straight cutting, their geometry is relatively simple.


The integral turning tool is standard on automatic threading machines and turret lathes and can be used in a wide range of turning applications in stainless steel. They all have V-brackets or shaft-type work brackets that can be used for roughing and finishing turning. V-shaped brackets are easily scratched and bitten when processing certain stainless steels, so shaft brackets are generally preferred. The shaft bracket must be mounted behind the cutting edge of the turning tool to eliminate the possibility of work hardening of the metal in front of the overall turning edge. In the symmetrical turning of large diameter stainless steel pipes, the overall turning tool is preferred because it provides a more rigid cutting condition. The blade on the overall turning tool should meet the requirements in size. This can avoid vibration and facilitate heat dissipation. 


Most of the turning edges of the turning tool are to open a V-groove for chipping or chip breaking, in order to cut off the long strips of chips, because these chips will prevent the tool from continuing to cut, and will also cut the parts. Smooth surface scratches. The V-groove cannot be broken at the secondary cutting edge of the tool as it will scratch the surface of the part. This type of turning tool has a long service life and can be used for deep cutting.


Sometimes when machining certain stainless steels with a single turning tool, it is best to have the chips fall under the lathe, rather than breaking them into smaller pieces. If the high-quality surface finish is required, the auxiliary process should be at least 0. 254 ~ 0. 508mm metal thickness while reducing the feed per revolution.


High-speed steel tools are best cut at normal speeds and feed rates. Cutting speed can be increased with high-drilling steel tools, but the cutting depth should be shallow to avoid tool wear and breakage. For example, the tensile strength range of 12Cr18Ni9 (302), Y12Cr18Ni9 (303), 06Cr19N10 (304) and 06Cr17N12Mo (316) under annealing conditions is approximately the same as the tensile strength range of carbon steel. However, the range between tensile strength and yield strength of austenitic stainless steels is much greater than for low or medium carbon ferritic steels. For example, there is a significant range between the tensile strength and yield strength of the annealed Y12Cr18Ni9 (303) steel, which causes “sticking” during cutting, resulting in accumulation at the tip of the tool, combined with poor precision, overheating and short tool life. . In order to avoid work hardening and reduce the accumulation of chips before cutting, when cutting austenitic large-diameter stainless steel pipes, a larger feed rate than carbon steel and a slower cutting speed are used. It is also recommended to use a helical chip cutter to cut all austenitic steels, especially high alloy steels such as 16Cr23N13 (309) steel, because the austenitic steels are very flexible and look like long ropes.



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