The as-cast structure of austenitic stainless steel castings is austenite + carbide or austenite + ferrite. Heat treatment can improve the corrosion resistance of austenitic stainless steel castings.
Equivalent Grade of Austenitic Stainless Steel |
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| AISI | W-stoff | DIN | BS | SS | AFNOR | U.N.E. / I.H.A. | JIS | UNI |
| 304 | 1.4301 | X5 CrNi 18 9 | 304 S 15 | 2332 | Z 6 CN 18.09 | F.3551 | SUS 304 | X5CrNi18 10 |
| 305 | 1.4303 | X5 CrNi 18 12 | 305 S 19 | - | Z 8 CN 18.12 | - | SUS 305 | X8CrNi19 10 |
| 303 | 1.4305 | X12 CrNiS 18 8 | 303 S 21 | 2346 | Z 10 CNF 18.09 | F.3508 | SUS 303 | X10CrNiS 18 09 |
| 304L | 1.4306 | X2 CrNiS 18 9 | 304 S 12 | 2352 | Z 2 CN 18.10 | F.3503 | SUS 304L | X2CrNi18 11 |
| 301 | 1.4310 | X12 CrNi 17 7 | - | 2331 | Z 12 CN 17.07 | F.3517 | SUS 301 | X12CrNi17 07 |
| 304 | 1.4350 | X5 CrNi 18 9 | 304 S 31 | 2332 | Z 6 CN 18.09 | F.3551 | SUS 304 | X5CrNi18 10 |
| 304 | 1.4350 | X5 CrNi 18 9 | 304 S 31 | 2333 | Z 6 CN 18.09 | F.3551 | SUS 304 | X5CrNi18 10 |
| 304LN | 1.4311 | X2 CrNiN 18 10 | 304 S 62 | 2371 | Z 2 CN 18.10 | - | SUS 304 LN | - |
| 316 | 1.4401 | X5 CrNiMo 18 10 | 316 S 16 | 2347 | Z 6 CND 17.11 | F.3543 | SUS 316 | X5CrNiMo17 12 |
| 316L | 1.4404 | - | 316 S 12/13/14/22/24 | 2348 | Z 2 CND 17.13 | SUS316L | X2CrNiMo17 12 | |
| 316LN | 1.4429 | X2 CrNiMoN 18 13 | - | 2375 | Z 2 CND 17.13 | - | SUS 316 LN | - |
| 316L | 1.4435 | X2 CrNiMo 18 12 | 316 S 12/13/14/22/24 | 2353 | Z 2 CND 17.13 | - | SUS316L | X2CrNiMo17 12 |
| 316 | 1.4436 | - | 316 S 33 | 2343 | Z 6 CND18-12-03 | - | - | X8CrNiMo 17 13 |
| 317L | 1.4438 | X2 CrNiMo 18 16 | 317 S 12 | 2367 | Z 2 CND 19.15 | - | SUS 317 L | X2CrNiMo18 16 |
| 329 | 1.4460 | X3 CrNiMoN 27 5 2 | - | 2324 | Z5 CND 27.05.Az | F.3309 | SUS 329 J1 | - |
| 321 | 1.4541 | X10 CrNiTi 18 9 | 321 S 12 | 2337 | Z 6 CND 18.10 | F.3553 | SUS 321 | X6CrNiTi18 11 |
| 347 | 1.4550 | X10 CrNiNb 18 9 | 347 S 17 | 2338 | Z 6 CNNb 18.10 | F.3552 | SUS 347 | X6CrNiNb18 11 |
| 316Ti | 1.4571 | X10 CrNiMoTi 18 10 | 320 S 17 | 2350 | Z 6 CNDT 17.12 | F.3535 | - | X6CrNiMoTi 17 12 |
| 309 | 1.4828 | X15 CrNiSi 20 12 | 309 S 24 | - | Z 15 CNS 20.12 | - | SUH 309 | X16 CrNi 24 14 |
| 330 | 1.4864 | X12 NiCrSi 36 16 | - | - | Z 12 NCS 35.16 | - | SUH 330 | - |
1. Solution Heat Treatment
The general specification of solution heat treatment is: heating the casting to 950°C - 1175°C and placing it in water, oil or air after the heat preservation to completely dissolve the carbides in the stainless steel to obtain a single-phase structure. The choice of solution temperature depends on the carbon content in the cast steel. The higher the carbon content, the higher the solid solution temperature required.
In order to reduce the temperature difference between the surface of the steel casting and the core during the heating process, the heating method of the solution treatment of austenitic stainless steel should be preheated at a low temperature and then quickly heated to the solution temperature. The holding time should increase correspondingly as the wall thickness of the casting increases.
The cooling medium for solution treatment can be water, oil or air, of which water is the most commonly used. Air cooling is only suitable for thin-walled steel castings.
Specifications of Solid Solution Treatment of Cast Austenitic Stainless Steel |
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| Grade in China | Equivalent Grade Abroard | Solution Temperature / ℃ | Hardness / HBW |
| ZG03Cr18Ni10 | / | 1050 - 1100 | / |
| ZG0Cr18Ni9 | / | 1080 - 1130 | / |
| ZG1Cr18Ni9 | G-X15CrNi18 8 (German Grade) | 1050 - 1100 | 140 - 190 |
| ZGCr18Ni9Ti | 950 - 1050 | 125 - 180 | |
| ZGCr18Ni9Mo2Ti | X18H9M2 (Russian Grade) | 1000 - 1050 | 140 - 190 |
| ZG1Cr18Ni12Mo2Ti | X18H12M2 (Russian Grade) | 1100 - 1150 | / |
| ZGCr18Ni11B | X18H11B (Russian Grade) | 1100 - 1150 | / |
| ZG03Cr18Ni10 | CF-3 (US Grade) | 1040 - 1120 | / |
| ZG08Cr19Ni11Mo3 | CF-3M (US Grade) | 1040 - 1120 | 150 - 170 |
| ZG08Cr19Ni9 | CF-8 (US Grade) | 1040 - 1120 | 140 - 156 |
| ZG08Cr19Ni10Nb | CF-8C (US Grade) | 1065 - 1120 (Stablization at 870 - 900 ) | 149 |
| ZG07Cr19Ni10Mo3 | CF-8M (US Grade) | 1065 - 1120 | 156 - 210 |
| ZG16Cr19Ni10 | CF-16F (US Grade) | 1095 - 1150 | 150 |
| ZG2Cr19Ni9 | CF-20 (US Grade) | 1095 - 1150 | 163 |
| ZGCr19Ni11Mo4 | CG-8M (US Grade) | 1040 - 1120 | 176 |
| ZGCr24Ni13 | 1095 - 1150 | 190 | |
| ZG1Cr24Ni20Mo2Cu3 | 1100 - 1150 | / | |
| ZG2Cr15Ni20 | CK-20 (US Grade) | 1095 - 1175 | 144 |
| ZGCr20Ni29Mo3Cu3 | CH-7M (US Grade) | 1120 | 130 |
| ZG1Cr17Mn13N | 1100 | 223 - 235 | |
| ZG1Cr17Mn13Mo2CuN | 1100 | / | |
| ZG0Cr17Mn13Mo2CuN | 1100 | 223 - 248 | |
2. Stabilization
Austenitic stainless steel has excellent corrosion resistance after solution treatment. However, when the casting is reheated to 500°C-850°C or the casting works in this temperature range, chromium carbide will re-precipitate along the austenite grain boundary, causing grain boundary corrosion or weld cracking. This phenomenon is called sensitization. In order to improve the intergranular corrosion resistance of such austenitic stainless steel castings, it is generally necessary to add alloying elements such as titanium and niobium. After solution treatment, reheat to 850°C - 930°C, and then quickly cool down. In this way, the carbides of titanium and niobium are first precipitated from the austenite, thereby preventing the precipitation of chromium carbide and improving the grain boundary corrosion resistance of the stainless steel.
Post time: Aug-18-2021