When turning high carbon steel, the cutting force and tool wear are larger than those in turning carbon steel because of the high carbon content. Therefore, lower cutting speeds should be used to reduce tool wear. Similar to the processing of low and medium carbon steels, the corresponding cutting speed should be adopted for workpieces with different hardness.

(4) Easy cut steel

Easy-cut steel is divided into re-vulcanized easy-cut steel (11XX series) and re-vulcanized, and then returned to phosphorus easy-cut steel (12XX series).

Re-vulcanized easy-cut steel (AISI 1108 ~ 1151) includes 14 standard grades. The processability of the material is improved when the sulfur content reaches 0.33% (AISI 1119 and AISI 1144). Most of the 11XX series grades increase the manganese content from 1.30% to 1.65% so that enough manganese reacts with sulfur to form MnS particles. Since the MnS particles will form some micropores and microcracks during the chip forming process, these microscopic defects will diffuse into the cut layer of the workpiece, which increases the shear angle of the chips and accelerates the chip breaking process, so that good processing can be obtained. surface.

Re-vulcanization and re-phosphorization easy-cut steels include four lead-free grades (AISI 1211, 1212, 1213 and 1215) and three lead-containing grades (AISI 12L13, 12L14 and 12L15) with lead content of 0.15% to 0.35. %. The 12XX series has increased sulfur content (0.10% to 0.35%) and phosphorus content (0.04% to 0.12%). The effect of increasing the sulfur content is similar to the case of the AISI 11XX grade.

After increasing the phosphorus content, the dissolution of phosphorus in iron can promote chip breaking, which is beneficial to avoid the formation of long tendril-like chips and obtain a better processed surface finish.

In turning, lead plays a role in the 12XX series of grades similar to an internal lubricant, which reduces friction between the tool and the workpiece and reduces heat generation. Leaded grades are mainly used for high volume processing. The use of lead-containing grades increases the cutting speed and results in a good machined surface, which increases processing efficiency by more than 25%.

Re-vulcanized, re-phosphorus easy-cut steel is widely used in the processing of threaded products. Due to economic reasons, the application of lead-free cut steel in high-speed machining of threads is limited, but its excellent processing characteristics can be fully reflected in the high-speed machining of threads.

Among all the easy-cut steels, the 12LXX grade is most suitable for high-speed turning. The cutting parameters are shown in Table 5 (omitted). There is no continuous chipping when turning easy-cut steel, so there is no chip control problem.

(5) High manganese steel

The manganese content of high manganese steel is 0.75% to 1.65%, the carbon content is 0.10% to 0.71%, and the phosphorus and sulfur contents are the same as those of low, medium and high carbon steels. There are 12 standard grades. Most grades contain 0.0005% to 0.30% boron, which can increase the thickness of the hardened layer.

15XX series low carbon high manganese steel (AISI 1513 ~ 1527) is mainly used for processing carburized parts with higher surface hardenability than ordinary carbon steel.

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