13-4 SR. Grid Resistors. Automotive Exhaust Components. Furnace High Temperature Applications. Applications Potential

Transcription

1 13-4 SR Stainless STEEL P r o d u c t D ata B u l l e t i n Grid Resistors Automotive Exhaust Components Locomotive Braking Resistors Resistance Heating Elements Furnace High Temperature Applications Applications Potential AK Steel 13-4 SR Stainless Steel is a ductile weldable ferritic with 13% Cr and 3.75% Al. The high aluminum content results in a base alloy with high electrical resistivity. It is intended for use where electrical energy needs to be dissipated or heat is generated. Good oxidation resistance to 18 F (982 C) permits applications at elevated temperatures. The alloy s wet corrosion resistance is comparable to ferritic alloys Type 49 or Type 43. The alloy is classified in ASTM B63 Class IV and as UNS Alloy K9147. UNS K S R s t a i n l e ss s t e e l

2 Table of Contents Product Description... 1 Physical Property Graphs... 2 Physical Properties... 3 Mechanical Properties... 4 Additional Mechanical Properties... 5 Formability... 6 Oxidation Resistance... 8 Corrosion Resistance... 9 Cyclic Sodium Chloride Pitting Test... 1 Boiling Condensate Corrosion Test Hot Salt Cycle Test Weldability... 13

3 Product Description AVAILABLE FORMS AK Steel produces 13-4 SR Stainless Steel in coils in thicknesses from in. ( mm) and widths up to and including 36 in. (914 mm). For lighter or heavier thicknesses contact your AK Steel representative. CHEMICAL COMPOSITION ASTM B63 Chemical requirements for Class IV Composition Range Resistivity Range % Cr % Al µohm cm COMPOSITION (wt %) Carbon.25 Manganese.3 Phosphorus Sulfur.45 max..3 max. Chromium 13. Nickel.25 Aluminum 3.75 Titanium.3 Iron Balance Typical ROOM TEMPERATURE MECHANICAL PROPERTIES.2% YS UTS Elongation Hardness ksi. (MPa) ksi. (MPa) % in 2" Rockwell 63 (434) 84 (579) 24 B81 Stretch rm value.9 Ridging Resistance Rating (2% stretch) 3 (Scale 1-5 with 5 the heaviest) Olsen Cup Height.35 in. (8.89 mm) (avg. of triplicate test) Bends: Passes 18 - T without fracturing <.5 in. (1.27 mm) thick PHYSICAL PROPERTIES Temperature vs. Density Temperature Density C F gm/cm 3 lbs./in

4 15 14 PHYSICAL PROPERTY Graphs Electrical Resistivity vs. Temperature Electrical Resistivity (1-6 ohm cm) SR SS 18 SR SS 18sr 134sr Temp. ( C) 9 Temp. ( F) Specific Heat vs. Temperature.9 Specific Heat (W s/g K) SR SS.4 Temp. ( C) Temp. ( F)

5 PHYSICAL PROPERTies 13-4 SR Stainless Steel has a mean coefficient of thermal expansion similar to 17-18% Cr alloys Type 439, 18 Cr-Cb and 18 SR Stainless Steels. These coefficients are significantly lower than for austenitic 3 series alloys. Mean Coefficient of Thermal Expansion Temperature CTE C F µin./in. C The thermal conductivity of 13-4 SR Stainless Steel is slightly lower than 18 SR and above 34 Stainless Steels. Thermal Conductivity Temperature Conductivity C F W/cm K BTU* *(BTU in./hr. ft. 2 F) 3

6 MECHANICAL PROPERTIES EFFECT OF COLD WORK Cold working 13-4 SR Stainless Steel leads to a rapid increase in yield and tensile strength and an accompanying loss of ductility. With 1% cold reduction, elongation falls below 1% and yield strength approaches 1 ksi. (69 MPa). The work hardening rate of 13-4 SR Stainless Steel is below that of carbon steel and austenitic stainless alloys. The n Value or work hardening coefficient (measured between 1% strain and the ultimate strenth) typically falls in the range of Stress, ksi. (MPa) 14 (965) 12 (827) 1 (689) 8 (552) 6 (414) 4 (276) 2 (138).2% YS UTS Elongation Elongation % in 2" (5.8 mm) % Cold Reduction HIGH TEMPERATURE TENSILE PROPERTIES Strength properties for 13-4 SR Stainless Steel decrease with heating showing a rapid decline once temperatures exceed 8 F (427 C).Conversely, elongation values remain reasonably unchanged up to 12 F (649 C) but show a rapid increase at higher temperatures. Stress, ksi. (MPa) 1 (689) 8 (552) 6 (414) 4 (276) 2 (138).2% YS UTS Elongation Elongation % in 2" (5.8 mm) Temperature ( C) Temperature ( F) 4

7 13-4 SR STAINLESS STEEL ADDITIONAL MECHANICAL PROPERTIES STRESS RUPTURE 885 F (475 C) Embrittlement 1 hour and 1 hour strengths at 12, 14, and 16 F (649, 74, and 871 C) are presented below. Strength decreases rapidly with temperature and time increases. The stress rupture strength of 13-4 SR Stainless Steel appears similar to that of 18 SR Stainless Steel. At temperatures between 75-1 F ( C), highly alloyed ferritic stainless steels can become embrittled. Strengths increase while ductility and bendability decrease. The degree of embrittlement increases with time, but can be eliminated with temperature excursions above 11 F (593 C). The properties and bend samples shown below indicate 13-4 SR Stainless Steel can become embrittled with time at 9 F (482 C). The alloy will recover much of its ductility with a one hour exposure to 115 F (621 C). Stress Rupture Strength Stress, psi. (MPa) to Rupture in Temp. F ( C) 1 Hours 1 Hours 12 (649) 675 (46.5) 45 (31.) 14 (76) 23 (15.9) 12 (8.3) 16 (871) 92 (6.3) 54 (3.7) EFFECT OF 9 F (482 C) SOAK ON MECHANICAL PROPERTIES Soak Duration (hrs.).2% YS ksi. (MPa) UTS ksi. (MPa) Elongation % in 2" Rockwell Hardness (1% - Ult.) 69 (476) 1 71 (49) 89 (614) 19.6 B (621) 19.4 B n Value 1 8 (552) 97 (669) 18.5 B (8) 129 (889) 1.1 C27-1* 76 (824) 98 (676) 18.5 B * 1 hours at 9 F (482 C) and 1 hour at 115 F (621 C) 13-4 SR Stainles Steel annealed grain microstructure Mixed ferritic grain structure of equiaxed ASTM GS#6 7 Etchant: Vilellas Reagent Annealed 9 F 9 F 9 F 1 hours 1 hours 1 hours 9 F 1 hours and 115 F 1 hour 5

8 13-4 SR 13-4SR pg6.pdf 11/27/211 6:5:44 PM STAINLESS STEEL FORMABILI FORMABILITY 13-4 SR TRUE STRESS/TRUE 13-4 SR STAINLESS STEELSTRAIN TRUE STRESS/TRUE STRAIN LONGITUDINAL ORIENTATION 13-4 SR Stainless Steel true stress/true strain curves are provided for the longitudinal and transverse sheet orientations. The transverse properties are somewhat stronger and less ductile. 1 True Stress (ksi) True True Stress Stress, (ksi) ksi. Toughness The ferritic microstructure with 3.75% Al makes 13-4 SR Stainless Steel more prone to brittle fracturing if impact loaded when cold. The ductile-to-brittle temperature for in. (2.5-3 mm) thick material falls between 9-1 F (32-38 C). The ductile-to-brittle temperature decreases and fracturing is less prone to occur as the sheet thickness decreases. Stamping and forming operations should be avoided below room temperature. Longitudinal Orientation True Strain True Strain(in./in.) (in/in) 13-4SR pg6.pdf 11/27/211 6:5:44 PM.2%.2%YS YS ksi. (MPa) ksi (MPa) UTS UTS ksi. (MPa) ksi (MPa) 6.8 (419) FORMABILITY 81.2 (56) 61 (421) True (ksi) True Stress Stress, ksi Major Engineering Strain (%) True Stress (ksi) 1.15 UTS ksi (MPa) Transverse to Sheet R.D. Transverse Orientation Forming Limit Curve AK Steel 13-4SR,.42" Thick Determined Using CamSys Localized Nodal Strain Measurement Method.1" Squa re Grid Pattern 8 Longitudinal to Sheet R.D. Transverse to Sheet R.D. 7 %) True Strain True Strain(in./in.) (in/in) 86 Thinning Thinning 7 2 n Elongation Hardness RB Value % in (419) 81.2 (56).167 Forming Limit Curve AK Steel 13-4SR,.42" Thick True Strain (in/in).2% YS ksi (MPa) Longitudinal to Sheet R.D B SR TRUE STRESS/TRUE 13-4 SR STAINLESS STEELSTRAIN 8 TRUE STRESS/TRUE STRAIN TRANSVERSE ORIENTATION Determined Using CamSys Localized Nodal Strain Measurement Method.1" Squa re Grid Pattern 13-4 SR TRUE STRESS/TRUE STRAIN LONGITUDINAL ORIENTATION 81 (558) Hardness n Value n Elongation Rockwell Elongation % in 2" Hardness (1% Ult.) RB Value % in % YS.2% YS ksi. (MPa) ksi (MPa) 65-4 (448)-3 1 Hardnessn Value n UTS UTS Elongation ElongationRockwell ksi. (MPa) % in 2" Hardness (1% Ult.) RB Value ksi (MPa) 85-2(586) (451) 85. (586) % in 2 22 B Minor Engineering Strain (%) Property Orientation to Sheet R.D. L Formability D T Tensile/Hardness Test (ASTM E8, E 694, E 18, A37) 13-4SR true stress/true curves %YS (ksi) 61.3 strain 64.6 areuts provided for the longitudinal (ksi) and 83.7 transverse orientations. % El. in 2" (man'l)sheet The 22.8 transverse properties are somewhat 6 ks 65

9 FORMABILITY The forming limit diagram is an experimentally developed graphical representation of the amount of biaxial strain or thinning a material can undergo during various forming operations (stretch, plane strain FLC, and draw) prior to onset of localized thinning and susequent fracture. The curves to the right were developed for.42 in. (1.1 mm) thick 13-4 SR Stainless Steel in both the longitudinal (parallel to the rolling direction) and transverse sample orientations. The FLC in the transverse direction is 14% versus 24% for the longitudinal. Tensile and stretch r data (lower right) were determined for sheet used to generate forming limit curves. Major Engineering Strain (%) Longitudinal to Sheet R.D. R.D. Transverse to Sheet R.D. Transverse Thinning to Sheet R.D. Thinning Minor Engineering Strain (%) Tensile/Hardness Test (ASTM E8, E694, E18, A37) Property Orientation to Sheet Rolling Direction L D T.2% YS (ksi.) UTS (ksi.) El. % in 2" (man l) n Value (1% - Ult.) Strength Coeff. (ksi.) HRBW 86 ASTM Grain Size 6/7 Stretch r (plastic strain ratio) at 18% (ASTM E517) Property Orientation to Sheet Rolling Direction L D T r r m.88 delta r.5 delta r (Max - Min).61 Ridging Rating 2 Olsen Cup Height (in.).369 LDR NA 7

10 OXIDATION RESISTANCE Cyclic oxidation comparisons at F ( C) show 13-4 SR Stainless Steel performs similar to higher Cr alloys Type 439, 18 Cr-Cb and 18 SR Stainless Steels and out performs austenitic Type 34. The 1 hour still air oxidation exposures show 13-4 SR Stainless Steel compares favorable to 18 SR Stainless Steel and superior to ferritic alloys 15 Cr-Cb Stainless Steel, 18 Cr-Cb Stainless Steel and austenitic alloy Type 39. Maximum service temperature appears to be 18 F (982 C) Cyclic Oxidation Resistance F ( C) Weight Change mg/cm 2 Alloy 1 Cycles 2 Cycles 3 Cycles 4 Cycles 5 Cycles Cr-Cb SS SR SS SR SS * Cycle = 25 min. Heat, 5 min. Cool 1 HOUR STILL AIR OXIDATION RESISTANCE Weight Gain (mg/cm 2 ) Temperature F ( C) Alloy 16 (871) 18 (982) 2 (193) 22 (124) 13-4 SR SS Cr-Cb SS NT 18 Cr-Cb SS NT 18 SR SS NT Not Tested T HOUR OXIDATION SAMPLES 13-4 SR SS 18 SR SS type Cr-Cb SS 2 F (193 C) 22 F (124 C) 8

11 13-4 SR STAINLESS STEEL Corrosion Resistance 13-4 SR Stainless Steel outperforms 11% Cr Type 49 and compares favorably to higher Cr ferritic stainless alloys in salt spray. ASTM B117 Salt Spray 5 Hours Type 49 Type SR SS 18 SR SS ASTM B117 specifies metallic coupons are inclined at 3 to the vertical and exposed to 5% NaCl solution atomized and continuously sprayed on to specimen surfaces while held at a temperature of 95 F (35 C). Five Cycles in ASTM G87 Moist SO2 Test Method B* Moist SO2 testing consists of an 8 hour exposure to 14 F (4 C) condensing humidity containing 2L of sulfur dioxide gas followed by a 16 hour ambient dwell. NOTE: One 24 hour period is equal to one cycle. 18 SR SS (A) 18 SR SS (B) 18 SR SS (C) 13-4 SR SS (3A) 13-4 SR SS (3B) 13-4 SR SS (3C) Samples were exposed to all five cycles after heat treatment for 3 minutes at 177 F (966 C). Samples were exposed to all five cycles without any heat treatment. 18 SR SS 13-4 SR SS Samples were exposed to one cycle before heat treatment for 3 minutes at 177 F (966 C) then an additional 4 cycles SR Stainless Steel performs as well if not better than 18 SR Stainless Steel in moist SO2 testing after 5 cycles with or without a 177 F (966 C) oxidation exposure. *ASTM Standard 21 Edition Volume 3.2 p. 372 Alternating 24 Hour Exposure Method 9

12 Cyclic Sodium Chloride Pitting Test Cyclic NaCl pitting tests consist of wetting coupons with salt solution, allowing the solution to concentrate as droplets, then dry, and remoisten at 85% RH. Heating cycles cause oxide films to form and lower resistance to pitting SR Stainless Steel resists corrosion similar to Type 439, better than Type 49 but not up to the level of 18 SR Stainless Steel. Heat treat 1hr at 8 F (427 C) Balance of the 24 hour period 14 F (6 C)/85% RH 15 minute 5% sodium chloride immersion 12 Salt Cycle Mass Loss after 28 days (2 cycles) Ambient dry 1 hour 45 minutes 1 Mass Loss (mg/cm 2 ) Pitting Corrosion in Exterior Salt Cycle Test In cyclic salt/humidity exposures 13-4 SR Stainless Steel falls between Type 439 and Type SR SS SR SS 49 Alloy Pit depth (µm) Type SR SS Type SR SS Days 1

13 Boiling Condensate Corrosion TEst The Boiling Condensate test exposes coupons to synthetic automotive exhaust condensate and concentrates the solution by boiling. Deposits are then remoistened in humidity. A 1 hour daily heating to 932 F (5 C) heat tints the specimens degrading corrosion resistance. By virtue of the 4% Al addition, 13-4 SR Stainless Steel in this test performs similar to higher Cr ferritic stainless steels and outperforms 11% Cr Type 49. In synthetic exhaust condensate 13-4 SR Stainless Steel compares favorably to the higher Cr alloys. Test Setup: Partial immersion of 2 x 4 in. (5.8 x 11.6 mm) coupon in synthetic condensate Test Solution: 5, ppm SO ppm Cl - 1 ppm NO 3-1 ppm Formic Acid Solution ph is adjusted to using sulfuric acid by adding approximately 3-4 ppm SO 4 2- Test Cycle Procedure: Heat 1 hour at 932 F (5 C) Humidity exposure for 7 hours at 14 F (6 C) / 85% RH 16 hours exposed to boiling test solution (boil to dryness) 6 weeks of testing Mass Loss (mg/cm 2 /yr) SR SS 18 SR SS Alloy Watch Glass Condensing Vapor Beaker Steel Sample Boiling Condensate 11

14 HOT SALT CYCLE TEST 13-4 SR Stainless Steel outperforms 11% Cr Type 49 and compares favorably to 18% Cr alloys (18 SR Stainless Steel and Type 439) when dipped in aqueous salt solutions and then exposed to 125 F (677 C) temperatures. Test Setup: 1. 9 minute heat treat at 125 F (677 C) 2. 1 minute cold water quench 3. 5 minute 5% NaCl soak 4. Repeat Cycle Steps 1-3 Samples in humidity overnight at 14 F (6 C) / 85% RH Cycle 2 Cycle Mass Loss (mg/cm 2 ) SR SS 18 SR SS 439 Alloy 12

15 Weldability The ferritic class of stainless steels is generally considered to be weldable by the common fusion and resistance techniques. Special consideration is required to avoid brittle weld fractures during fabrication by minimizing discontinuities, and maintaining low weld heat input. This particular alloy is generally considered to have slightly poorer weldability than the most common alloy of this stainless class, Type 49. A major difference is that the weld deposits themselves, while possessing reasonable ductility, may not be as ductile as the base metal. Gas tungsten arc welds in.42 in SR Stainless Steel sheet, both with and without filler, were bend tested according to ASTM E29 around a.5 in. diameter bar. All of the weld face and root bend tests passed with no cracking, indicating that the welds do have good ductility. When a weld filler is required, 18 Cb filler is suggested for high-temperature service. Care should be taken to avoid forming welds in cold weather. ER38L filler is suggested for better weld ductility in ambient temperature conditions. The specific alloy selection depends on the application. Type 49 Stainless Steel is well known in reference literature and more information can be obtained in the following ways: 1. ANSI/AWS A5.9, A5.22, and A5.4 (filler metals, minimum UTS and elongation). 2. Welding of Stainless Steels and Other Joining Methods, SSINA, (8: ). 3. Welding Stainless Steels, FDB #SF

16 AK Steel Corporation 9227 Centre Pointe Drive West Chester, OH Headquartered in West Chester, Ohio, AK Steel is a world leader in the production of flatrolled carbon, stainless and electrical steel products, primarily for automotive, appliance, construction and electrical power generation and distribution markets. The company operates seven steel plants and two tube manufacturing plants across four states Indiana, Kentucky, Ohio and Pennsylvania. All of the company s steel plants are ISO/TS 16949, ISO 91 and ISO 141 certified for their quality and environmental management systems. AK Steel is a publicly held company traded over the New York Stock Exchange under the symbol AKS aligning the company with many of the most prominent corporations in America. 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. Revision