12 SR STAINLESS STEEL. More Oxidation Resistant Than Type 409. More Creep Resistant Than Type 409. Applications Potential

Transcription

1 12 SR STAINLESS STEEL P R O D U C T D ATA B U L L E T I N More Oxidation Resistant Than Type 409 More Creep Resistant Than Type 409 Applications Potential AK Steel 12 SR Stainless Steel was developed specifically for automotive exhaust gas applications. Typical uses include passenger car and truck catalytic converters, stamped and tubular manifolds, flanging and tubing associated with exhaust system components. Non-automotive applications include heat exchangers, flue liners and commercial furnaces. 1 2 S R S TA I N L E S S S T E E L

2 TABLE OF CONTENTS Product Description... 1 Physical Properties... 1 Mechanical Properties... 2 Formability... 4 Elevated Sag Resistance... 6 Oxidation Resistance... 7 Weldability... 9

3 PRODUCT DESCRIPTION 12 SR is a 12% chromium ferritic stainless steel that provides a more oxidationresistant, stronger alternative to Type 409 stainless steel. In addition, it provides formability and weldability comparable to other more highly alloyed ferritic stainless steels. COMPOSITION (wt %) Carbon (C) Silicon (Si) 0.60 Chromium (Cr) 12.0 Aluminum (AL) 1.20 Titanium (Ti) 0.25 Niobium (Nb) 0.50 AVAILABLE FORMS 12 SR Stainless Steel is available as sheet and strip. Data presented in this bulletin were generated by testing material annealed at 1950 F (1066 C) unless otherwise stated. PHYSICAL PROPERTIES Density, g/cm 3 (lbs./in. 3 ) Modulus of Elasticity, psi. (GPA) Type (0.276) 7.63 (0.278) in tension 27.5 x 10 6 (189) 1

4 MECHANICAL PROPERTIES TABLE 1 TYPICAL MECHANICAL PROPERTIES* Test Direction % in 2" (50.8 mm) Rockwell Hardness 12 SR Longitudinal 73 (503) 50 (345) 32.0 B81 Type 409 Longitudinal 64 (441) 36 (248) 35.0 B70 *1950 F (1066 C) Anneal. TABLE 2 PROPERTIES ACCEPTABLE FOR MATERIAL SPECIFICATION* % in 2" (50.8 mm) Rockwell Hardness 12 SR 60 (448) min. 35 (276) min. 20 min. B92 max. Type (379) 30 (207) 22 min. B80 max. *1950 F (1066 C) annealed sheet and strip. TABLE 3 EFFECT OF ANNEALING TEMPERATURE ON MECHANICAL PROPERTIES* Annealing % in 2" (50.8 mm) Rockwell Hardness 2050 (1121) 65.0 (449) 43.2 (297) 37.5 B (1066) 65.3 (451) 43.3 (298) 36.5 B (1010) 69.8 (482) 44.7 (309) 34.5 B (954) 72.2 (499) 44.9 (310) 32.5 B (899) 77.8 (537) 50.1 (346) 27.0 B84 *Average of triplicated longitudinal tests. TABLE 4 EFFECT OF COLD WORK ON MECHANICAL PROPERTIES* % Cold Work % in 2" (50.8 mm) Rockwell Hardness (499) 49.4 (340) 32.0 B (608) 82.6 (569) 15.0 B (684) 92.0 (634) 10.0 B (748) (724) 6.0 B (774) (743) 5.0 C (818) (799) 3.0 C (870) (844) 4.0 C24 *Average of duplicate tests. 2

5 TABLE 5 EFFECT OF PRIOR COLD WORK ON ANNEALED MECHANICAL PROPERTIES* % Cold Work Annealing % in 2" (50.8 mm) Rockwell Hardness (996) 73.8 (509) 48.8 (337) 30.0 B (1066) 66.4 (457) 42.4 (292) 35.0 B80 4 ASTM Grain Size (966) 74.2 (511) 45.6 (314) 30.0 B81 6-1/ (1066) 66.6 (459) 43.8 (302) 35.0 B (996) 75.2 (518) 48.4 (333) 29.0 B80 7 *Average of duplicate tests (1066) 68.1 (469) 44.4 (306) 32.0 B79 5 TABLE 6 ROOM TEMPERATURE REVERSE BENDING FATIGUE (SONNTAG) Stress *Run Out. Longitudinal Number of x 10 3 Transverse 50 (344) (310) (303) (296) (289) (282) (276) (269) (262) (258) 18098* 37 (255) * 36 (248) 10212* 35 (241) * * 3

6 FORMABILITY Use the same techniques employed with Type 409 to fabricate 12 SR Stainless Steel. In the annealed condition, the alloy exhibits good bend ductility. Similar to other ferritic stainless steels, formability decreases with increases in thicknesses, particularly above in. (3.2 mm) thick. In tubular form, the material does not fabricate as easily as Type 409 unless an annealing cycle is included TABLE 7 FORMABILITY Annealing Olsen Cup Height in. (mm) Limiting Draw Ratio after welding. For maximum elevated temperature creep strength, a 1950 F (1066 C) anneal at temperature for several minutes is suggested. Following the anneal, air cooling is usually sufficient. To minimize grain size, a lower temperature anneal cycle is beneficial. Contact AK Steel for guidance in selecting the optimum cycle for applications other than creep resistance. ELEVATED TEMPERATURE STRENGTH Laboratory tests show that 12 SR Stainless Steel is stronger at elevated temperatures than Type 409. This strength advantage holds at high strain rates such as with short-time elevated temperature tensiles (Table 8) and with low strain rates such as with sag testing (Figures 1 and 2). TABLE 8 SHORT-TIME ELEVATED TEMPERATURE TENSILE PROPERTIES* Room 73.0 (504) 50.0 (329) 1000 (538) 53.4 (368) 28.4 (196) 1200 (649) 43.7 (301) 23.9 (164) 1300 (704) 21.6 (149) 16.2 (111) 1400 (760) 10.1 (70) 8.1 (56) 1500 (816) 7.5 (52) 6.1 (42) 1600 (871) 5.2 (35) 4.2 (29) *Average of duplicate tests. TABLE 9 STRESS RUPTURE STRENGTH Minimum 180 Bend Diameter 1825 (996) 395 (10.0) 2.10 OT 3 in. (76 mm) Stretch Cup Height, in. (mm) 1950 (1066) 390 (9.9) 2.13 OT 1.16 (29.4) *0.060 in. (1.5 mm) thickness. Stress, for Rupture in 100 Hours 1000 Hours 1300 (704) 6.0 (41) 4.2 (29) 1500 (816) 2.3 (16) 1.5 (10) 4

7 TABLE 10 EFFECT OF ELEVATED TEMPERATURE EXPOSURE ON 1500 F (816 C) STRESS-RUPTURE STRENGTH* % Cold Work Exposure Exposure Time, Hours Stress, for Rupture in 100 Hours 1000 Hours (593) (17.5) 1.6 (11.2) (15.4) 1.3 (9.1) (15.4) 1.3 (9.1) (593) (18.2) 1.6 (11.2) (16.1) 1.3 (9.1) (16.1) 1.3 (9.1) (704) (16.8) 1.6 (11.2) (15.4) 1.3 (9.1) (16.1) 1.2 (8.4) (704) (16.1) 1.5 (10.5) (14.7) 1.3 (9.1) (14.0) 1.3 (9.1) (816) (13.3) 1.4 (9.8) (12.6) 1.2 (8.4) (12.6) 1.2 (8.4) (816) (12.6) 1.3 (9.1) (12.6) 1.2 (8.4) (11.9) 1.2 (8.4) * in. ( mm) thick sheet. Samples were cold worked and aged at F ( C) prior to stress rupture testing. TABLE 11 EFFECT OF ELEVATED TEMPERATURE EXPOSURE ON ROOM-TEMPERATURE PROPERTIES* Prior % Cold Work Exposure Exposure Time, Hours % in 2" (50.8 mm) Rockwell Hardness Minimum 180 Bend Diameter (593) (582) 45.6 (314) 25.0 B86 2T (714) 74.5 (514) 18.0 B97 2T (769) 85.9 (593) 16.0 B99 4T (593) (580) 44.8 (309) 26.0 B86 2T (711) 72.0 (496) 18.0 B96 2T (760) 85.0 (586) 16.0 B99 4T (704) (509) 39.4 (272) 30.0 B80 2T (547) 52.3 (360) 24.0 B86 2T (563) 55.6 (383) 21.0 B88 0T (704) (504) 41.6 (287) 31.0 B80 1T (519) 49.6 (342) 25.0 B84 2T (540) 56.2 (387) 23.0 B84 0T (816) (464) 37.8 (261) 34.0 B76 0T (476) 46.8 (323) 31.0 B80 1T (468) 42.0 (290) 32.0 B76 0T (816) (456) 37.4 (258) 35.0 B76 0T (468) 45.0 (310) 30.5 B80 1T (457) 39.8 (274) 34.0 B74 0T * in. ( mm) thick sheet. Samples were cold worked and aged prior to conducting room temperature tensile tests. 5

8 ELEVATED TEMPERATURE SAG RESISTANCE FIGURE F (871 C) SAG TESTS Deflection, mils SR Type 444 Type 409 The sag test is a simple technique used to compare the elevated temperature deformation or creep resistance of various alloys. Strips 1 x 12 in. (25.4 x 305 mm), all of the same thickness, are placed on a specially constructed rack with an unsupported span of 10 in. (254 mm). Samples are then exposed to varying time periods at a specified temperature. After each time interval, sample deflection is measured with a dial gauge. Sag curves represent deflection vs. time at a set temperature or deflection vs. temperature for a set time. Sag results correlate well with actual creep tests. At 1600 F (871 C), 12 SR Stainless Steel is considerably more resistant to sag deflection than Type 409, and comparable to Type 444 stainless steel as shown in Figure 1. This strengthening under low strain rate-elevated temperature conditions is attributed to a high final annealing temperature and the subsequent formation of secondary phases in the microstructure of the 12 SR material. FIGURE HOUR SAG EXPOSURES Exposure, Hrs. Deflection, in. (mm) (10.2) (7.6) (5.1) (2.5) 12 SR.06 in. (1.5 mm) Type in. (1.5 mm) Type in. (2.5 mm) (593) 1200 (649) 1300 (704) 1400 (760) 1500 (818) 1600 (871) 1700 (927), Sag deflections after 100 hours at varying temperatures show AK Steel 12 SR comparable to a much thicker Type 409 stainless (Figure 2). ELEVATED TEMPERATURE FATIGUE STRENGTH In typical tension-tension fatigue tests (R=0.1) at 1500 F a stress of 3.5 ksi. (24 MPa) can be maintained of more than 10 7 cycles without failure. 6

9 OXIDATION RESISTANCE Cyclic oxidation test data in Tables 12, 13 and 14 indicate that 12 SR Stainless Steel is comparable to Type 409 at 1400 F (760 C), superior to Types 409 and 430 at 1600 F (871 C), and approaches the 18% Cr ferritic stainless steels up through 1700 F (927 C) in resisting weight gain through oxidation. TABLE 12 CYCLIC OXIDATION TESTS AT 1400 F (760 C)* Weight Change, mg/cm SR Type *Furnace atmosphere natural gas. 25 minutes heat, 5 minutes cool. TABLE 13 CYCLIC OXIDATION TESTS AT 1600 F (871 C)* Weight Change, mg/cm SR Type Type ** Type ** 18 SR *Furnace atmosphere natural gas. 25 minutes heat, 5 minutes cool. **Removed from test. TABLE 14 CYCLIC OXIDATION TESTS AT 1700 F (927 C)* Weight Change, mg/cm SR Type SR *Furnace atmosphere natural gas. 25 minutes heat, 5 minutes cool. 7

10 TABLE 15 OXIDATION RESISTANCE 100-HOUR STILL AIR RESISTANCE Thickness in. (mm) Weight Change, mg/cm 2, 1500 (816) 1650 (899) 1725 (940) 1800 (982) 1900 (1038) 12 SR (1.5) (0.76) (0.38) (0.13) Type (1.5) (0.76) (0.38) * (0.13) 1.8 * Type (0.76) * *Catastrophically destroyed (0.38) * (0.13) * CORROSION RESISTANCE TABLE 16 SYNTHETIC MUFFLER CONDENSATE* Corrosion Rate 240 Hours mils/year μm/year 12 SR Type *Exhaust condensate due to incomplete combustion. 8

11 WELDABILITY 12 SR Stainless Steel is weldable by Gas Metal Arc (GMAW), Gas Tungsten Arc (GTAW) and resistance welding techniques. Weld formability approaches that of Type 409, but because of the higher alloy content, may not be equal to Type 409. Qualification trials should precede any commercial production requiring high-frequency weld fabrication. TABLE 17 RESISTANCE SPOT WELDING PROPERTIES* Tension Sheer and U-Tension Tests Welding Electrodes in. (6.3 mm) Flat Face 3 in. (76 mm) Radius RWMA Class 2 *0.060 in. (1.5 mm) thickness. Tension Shear Test Load, lbs. (N) 2660 (3678) 2785 (3850) 2860 (3954) 3010 (4161) U-Tension Test Load, lbs. (N) 885 (1224) 800 (1106) 705 (975) 1110 (1535) Filler metal can be used. The specific alloy selection depends on the application. Contact AK Steel sales for assistance in selecting a suitable weld filler metal. Ductility Ratio Average U-Tension Load Average Tension Shear Load = = TABLE 18 GAS TUNGSTEN-ARC WELD PROPERTIES (AUTOGENOUS) Thickness in. (mm) % in 2" (50.8 mm) Failure Location Olsen Cup Height in. (mm) 0.60 (1.5) 68.1 (469) 31.5 Base metal 435 (11.0) (2.9) 69.5 (479) 31.0 Base metal * F Weld face in tension. ** R Weld root in tension. ***Minimum diameter is measured in the number of thicknesses of material around which the bend is made. OT is the same as flat. Minimum 180 Bend Diameter*** F* 0T R** 0T F* 0T R** 3T 9

12 Volume Resistivity µω Cm FIGURE 3 12 SR VOLUME RESISTIVITY Type 409 Volume Resistivity at Room 60.0 Microhm cm , F , C TABLE 19 TOUGHNESS OF AUTOGENOUS GTA WELDS* Test W/A, in.-lbs./in. 2 (mm N/mm 2 ) Longitudinal Transverse 212 (100) 3687 (645) 4038 (707) 150 (66) 3829 (670) 2677 (468) 72 (22) 2933 (513) 423 (74) 32 (0) 120 (21) 378 (66) 0 (-18) 120 (21) 193 (34) *0.060 in. (1.5 mm) thickness, notch in weld. TABLE 20 THERMAL CONDUCTIVITY Thickness in. (mm) 12 SR 400 (204) 800 (427) 1200 (649) 1600 (871) Type 409/Type (100) 932 (500) Thermal Conductivity BTU/hr./ft. 2 /ft./ F (W/m K) 11.1 (19.2) 12.7 (21.9) 14.0 (24.2) 15.3 (24.9) 14.4 (24.9) 16.6 (28.7) TABLE 21 THERMAL EXPANSION Test Mean Coefficient of Thermal Expansion µω/in./ F (μm/m C) (21-93) 5.7 (10.3) (21-204) 6.0 (10.8) (21-316) 6.1 (11.0) (21-427) 6.4 (11.5) (21-538) 6.6 (11.9) (21-653) 6.9 (12.4) (21-760) 7.0 (12.6) (21-871) 7.4 (13.3) 10

13 AK Steel Corporation 9227 Centre Pointe Drive West Chester, OH STEEL AK Steel is a world leader in the production of flat-rolled carbon, stainless and electrical steel products, primarily for automotive, infrastructure and manufacturing, construction and electrical power generation and distribution markets. Headquartered in West Chester, Ohio (Greater Cincinnati), the company employs approximately 8,000 men and women at eight steel plants, two coke plants and two tube manufacturing plants across six states: Indiana, Kentucky, Michigan, Ohio, Pennsylvania and West Virginia. Additional information about AK Steel is available at The information and data in this document are accurate to the best of our knowledge and belief, but are intended for general information only. Applications suggested for the materials are described only to help readers make their own evaluations and decisions, and are neither guarantees nor to be construed as express or implied warranties of suitability for these or other applications. Data referring to material properties are the result of tests performed on specimens obtained from specific locations of the products in accordance with prescribed sampling procedures; any warranty thereof is limited to the values obtained at such locations and by such procedures. There is no warranty with respect to values of the materials at other locations. AK and the AK Steel logo are registered trademarks of the AK Steel Corporation