As the name implies, free cutting steel has an excellent cutting performance. It can be processed by higher cutting speed and deeper cutting depth. The free cutting elements such as lead, sulfur, calcium, selenium, tellurium, and bismuth in steel can reduce the cutting resistance and the abrasion of machined parts, improve the smoothness and accuracy as well as the tool service life.
According to its features, stainless steel can be divided into non-magnetic stainless steel, free cutting stainless steel, low-temperature stainless steel, high strength stainless steel. Addition of 0.2 ~ 0.4% sulfur and selenium as impurity elements in stainless steel can improve the cutting performance of stainless steel because they reduce the toughness of stainless steel. For example, the impact value of 18-8 stainless steel can reach 30kg/cm². The impact value of steel 18-8 containing 0.31% sulfur (0.084% C, 18.15% Cr, 9.25% Ni) is 1.8kg /cm². The impact value of steel 18-8 containing 0.22% selenium (0.094% C, 18.4% Cr, 9% Ni) is 3.24kg /cm². Today here we have sorted out the commonly used free cutting stainless steel and their chemical composition.
UNS | S20300 | S30300 | S30310 | S30323 | S30345 |
Type | XM-1 | 303 | XM-5 | 303Se | XM-2 |
C | ≤0.08 | ≤0.15 | ≤0.15 | ≤0.15 | ≤0.15 |
Si | ≤1.00 | ≤1.00 | ≤1.00 | ≤1.00 | ≤1.00 |
Mn | 5.00 6.50 | ≤2.00 | 2.5 4.5 | ≤2.00 | ≤2.00 |
P | ≤0.04 | ≤0.20 | ≤0.20 | ≤0.20 | ≤0.05 |
S | 0.18 0.35 | ≥0.15 | ≥0.25 | ≤0.06 | 0.11 0.16 |
Cr | 16.00 18.00 | 17.00 19.00 | 17.00 19.00 | 17.00 19.00 | 17.00 19.00 |
Ni | 5.00 6.50 | 8.00 10.00 | 7.00 10.00 | 8.00 10.00 | 8.00 10.00 |
Mo | — | — | — | — | 0.40 0.60 |
Se | — | — | — | ≥0.15 | — |
Cu | 1.75 2.25 | — | — | — | — |
Al | — | — | — | — | 0.60 1.00 |
UNS | S41600 | S41610 | S41623 | S42020 | S44020 |
Type | 416 | XM-6 | 416Se | 420F | 440F |
C | ≤0.15 | ≤0.15 | ≤0.15 | 0.30 0.40 | 0.95 1.20 |
Si | ≤1.00 | ≤1.00 | ≤1.00 | ≤1.00 | ≤1.00 |
Mn | ≤1.25 | 1.50 2.50 | ≤1.25 | ≤1.25 | ≤1.25 |
P | ≤0.06 | ≤0.06 | ≤0.06 | ≤0.06 | ≤0.06 |
S | ≥0.15 | ≥0.15 | ≤0.06 | ≥0.15 | ≥0.15 |
Cr | 12.00 14.00 | 12.00 14.00 | 12.00 14.00 | 12.00 14.00 | 16.00 18.00 |
Ni | — | — | — | (≤0.5) | (≤0.5) |
Se | — | — | ≥0.15 | — | — |
Cu | — | — | — | (≤0.6) | (≤0.6) |
UNS | S18200 | S18235 | S41603 | S43020 | S43023 |
Type | XM-34 | — | — | 430F | 430FSe |
C | ≤0.08 | ≤0.025 | ≤0.08 | ≤0.12 | ≤0.12 |
Si | ≤1.00 | ≤1.00 | ≤1.00 | ≤1.00 | ≤1.00 |
Mn | ≤2.50 | ≤0.50 | ≤1.25 | ≤1.25 | ≤1.25 |
P | ≤0.04 | ≤0.03 | ≤0.06 | ≤0.06 | ≤0.06 |
S | ≥0.15 | 0.15 0.35 | ≥0.15 | ≥0.15 | ≤0.06 |
Cr | 17.50 19.50 | 17.50 18.50 | 12.00 14.00 | 16.00 18.00 | 16.00 18.00 |
Ni | — | ≤1.00 | — | — | — |
Mo | 1.50 2.50 | 2.00 2.50 | — | — | — |
Se | — | — | — | — | ≥0.15 |
Ti | — | 0.30 1.00 | — | — | — |
N | — | ≤0.025注 | — | — | — |
Note：C+N≤0.03