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Stainless Steel Castings, Grey Iron Castings, Ductile Iron Castings

Heat Treatment of Austenitic Stainless Steel Castings

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

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

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