Austenitic Chromium-Manganese Stainless Steels – a European Approach

Austenitic Chromium-Manganese Stainless Steels – A European Approach

Materials and Applications Series, Volume 12 Austenitic Chromium-Manganese Stainless Steels – A European Approach

Euro Inox

Euro Inox is the European market development asso- Full members ciation for stainless steel. Acerinox The members of Euro Inox include: www.acerinox.es • European stainless steel producers Aperam • national stainless steel development associations www.aperam.com • development associations of the alloying element industries Outokumpu www.outokumpu.com A prime objective of Euro Inox is to create awareness of the unique properties of stainless steels and to ThyssenKrupp Acciai Speciali Terni promote their use in existing applications and new www.acciaiterni.it markets. To this end, Euro Inox organises conferences ThyssenKrupp Nirosta and seminars and issues guidance in printed form www.nirosta.de and electronic format, to enable architects, design- ers, specifiers, fabricators and end users to become more familiar with the material. Euro Inox also sup- Associate members ports technical and market research. Acroni www.acroni.si

British Stainless Steel Association (BSSA) www.bssa.org.uk

Cedinox www.cedinox.es

Centro Inox www.centroinox.it

Informationsstelle Edelstahl Rostfrei www.edelstahl-rostfrei.de

International Chromium Development Association (ICDA) www.icdachromium.com

International Molybdenum Association (IMOA) www.imoa.info

Nickel Institute www.nickelinstitute.org

Paslanmaz Çelik Derneği (PASDER) www.turkpasder.com

Polska Unia Dystrybutorów Stali (PUDS) ISBN 978-2-87997-321-0 www.puds.pl 978-2-87997-333-3 German version SWISS INOX 978-2-87997-335-7 Italian version www.swissinox.ch Austenitic Chromium-Manganese Stainless Steels – A European Approach

Contents

Austenitic Chromium-Manganese Stainless Steels - 1. Introduction 2 A European Approach 2. History of the 200 series and current First Edition 2012 developments 3 (Materials and Applications Series, Volume 12) 3. The new 200 European grade: 1.4618 5 © Euro Inox 2012 4. Mechanical properties 6 5. Formability 9 6. Corrosion resistance properties 12 7. Physical properties 14 8. Weldability 15 9. Summary 16 10. References 17

Editor Euro Inox Diamant Building, Bd. A. Reyers 80 1030 Brussels, Belgium Tel.: +32 2 706 82 67 Fax: +32 2 706 82 69 E-mail: [email protected] Internet: www.euro-inox.org

Authors J. Charles, La Plaine Saint Denis, France A. Kosmač, Brussels, Belgium J. Krautschick, Krefeld, Germany Copyright notice J. A. Simón, Los Barrios (Cádiz), Spain This work is subject to copyright. Euro Inox reserves N. Suutala, Espoo, Finland all rights of translation in any language, reprinting, re- T. Taulavuori, Tornio, Finland use of illustrations, recitations and broadcasting. No part of this publication may be reproduced, stored in Disclaimer a retrieval system, or transmitted in any form or by any Euro Inox has made every effort to ensure that the means, electronic, mechanical, photocopying, record- information presented in this publication is techni- ing or otherwise, without the prior written permis- cally correct. However, the reader is advised that the sion of the copyright owner, Euro Inox, Luxemburg. material contained herein is for general information Violations may be subject to legal proceeding and purposes only. Euro Inox, its members, staff and con- liable for monetary damages per infringement as well sultants, specifically disclaim any liability or respon- as cost and legal fees and fall under prosecution act of sibility for loss, damage or injury, resulting from the the Luxemburg copyright law and regulations within use of the information contained in this document. the European Union.

1 Austenitic Chromium-Manganese Stainless Steels – A European Approach

1 Introduction

Replacing nickel in austenitic stainless steels references for these grades has recently by adding manganese has been considered been pointed out, along with: for over 50 years. The purpose is to reduce • an over-generalised use of these grades the impact of nickel-price fluctuations on the as a supposed alternative to grade 1.4301 alloy surcharge. This has resulted in the de- (304); velopment of the so-called 200 series. These • the emergence of other type 200 steels grades also have complementary nitrogen with low Cr and Ni contents, high levels additions, to further stabilise the austenitic of impurities and ill-defined mechanical phase and provide high-strength properties properties; necessary in certain applications. Copper • the fact that the non-magnetic nature of has also been successfully added, to provide these grades means customers can eas- austenite stabilisation and improve cold- ily mistake them for austenitic chromium- forming properties. When copper is added, nickel grades. nitrogen content can be reduced, providing softer manganese austenitic grades. In Europe, the wish to be less affected by the alloy surcharge has resulted in the develop- In Europe and North America, these grades ment of the ferritic grades. However, these had only limited applications until the end are more difficult to weld, especially beyond of the last century. They were selected main- a thickness of 6 mm. In some applications, ly for their combination of high strength and non-magnetic – i.e. austenitic – material is ductility, for example in the production of preferable. It was therefore desirable to make conveyor belts. available a type 200 stainless steel with: • an adequate and consistent level of cor- In India, due to restrictions on nickel im- rosion resistance; ports, type 200 stainless steels have been • mechanical properties that make it easier extensively used since the 1980s, essential- to form than the “classic” grade 1.4372 ly for affordable stainless steel tableware. (201). As these items are typically washed by hand and not exposed to the more corrosive con- For CrMn stainless steel to become more ac- ditions of dishwashers, their corrosion re- ceptable in a European environment, a high sistance has proved entirely adequate. level of standardisation is required. Provid- ing technical information has been made a More recently, large amounts of type 200 priority, to avoid misunderstandings and stainless steels have been produced in Asia. improper use. Some of the grades developed have not met current international standards, since To respond to these needs, a working group they have been designed to minimize alloy- with representatives of the main European ing elements – including chromium, which flat stainless steel producers was created, is a key element in corrosion resistance. under the umbrella of Euro Inox. Its main con- The lack of international standards and clusions are presented in this publication.

2 Austenitic Chromium-Manganese Stainless Steels – A European Approach

2 History of the 200 series and current developments

The 200 series of stainless steels was de- Simultaneously, Mn and Cu containing veloped in the early 1930s. Although the grades were developed which made it pos- first chemical analyses were of the 205 kind sible to produce 4–6 % Ni austenitic grades (Ni content close to 1 % and stabilisation of (grades 211 and 203) with relatively low ni- the austenitic phase by simultaneous high trogen content (<0.06 % N). Drawing prop- manganese and nitrogen additions – see erties equivalent to those of 304 could be Figures 1 and 2), the first grades to receive achieved. Due to a new Ni shortage, these the AISI label in the mid-1950s were the grades began to be popular in the early 201 and 202 grades (nickel content around 1970s. The new AOD technology made add- 4–6 % and nitrogen additions below 0.25 %). ing nitrogen to the 200 series easier and These became more popular during the Ko- more cost-effective (Table 1). Once again the rean War, due to the need to conserve nickel. nickel shortage ended and, with high avail- At that time, the use of nickel was mainly res- ability, Ni prices went down again. For more tricted to military applications. Grade 214, than 30 years, grade 304 was the standard with less than 1 % Ni and about 0.35 % N was of the stainless steel family, at an average produced at the end of the 1950s. Auste- yearly growth of 5–6 %. nitic CrMn grades containing Mo to improve corrosion resistance appeared in the mid- 1960s, both in the U.S. and Europe.

N Cr (%) (%) 5 % Ni Austenite + Ferrite 12 % Mn 0,5 4 % Ni 8 % Mn 18 4 % Mn 3 % Ni 1 % Mn 0,4 2 % Ni 16 1 % Ni

0,3 0 % Ni 14 Austenite 0,2 5 4 3 2 1 0 % Ni

Cr Mn 18 20 22 24 26 28 (%) 2691215 (%)

Figure 1. Effects of Cr and Mn additions on N solubility Figure 2. Alloying elements and austenite loop stabili- in steel ty at 1075 °C (Franks)

3 Austenitic Chromium-Manganese Stainless Steels – A European Approach

The 200 series still had only marginal appli- began. China, especially, became a major cations in the eighties and nineties (with the user of 200 series stainless steel. Austenitic exception of India). With the new century, a CrMn steel was produced locally, the rest new period of high nickel-price volatility being imported mainly from India.

Table 1 . Chemical analyses of different austenitic CrMn grades in % by mass (200 series)

AISI * UNS ** Cr Ni Mn N C S Others 201 S20100 16.0–18.0 3.5—5.5 5.5—7.5 0.25 max. 0.15 max. 0.030 max. S20103 16.0–18.0 3.5—5.5 5.5—7.5 0.25 max. 0.03 max. 0.030 max. 201LN S20153 16.0–17.5 4.0—5.0 6.4—7.5 0.10—0.25 0.03 max. 0.030 max. Cu 1.0 max. S20161 15.0–18.0 4.0—6.0 4.0—6.0 0.08—0.20 0.15 max. 0.040 max. 202 S20200 17.0–19.0 4.0—6.0 7.5—10.0 0.25 max. 0.15 max. 0.030 max. 203 S20300 16.0–18.0 4.0—6.0 5.0—6.5 - 0.08 max. 0.18—0.35 Cu 1.75—2.25 204 S20400 15.0–17.0 1.5—3.0 7.0—9.0 0.15—0.30 0.03 max. 0.030 max. S20430 15.5–17.5 1.5—3.5 6.5—9.0 0.05—0.25 0.15 max. 0.030 max. Cu 2.0—4.0 205 S20500 15.5–17.5 1.5—3.5 14.0—15.5 0.32—0.40 0.12—0.25 0.030 max. 214 S21400 17.0–18.5 1.0 max. 14.0—16.0 0.35 min. 0.12 max. 0.030 max. 216 S21600 17.5–22.0 5.0—7.0 7.5—9.0 0.25—0.50 0.08 max. 0.030 max. Mo 2.0—3.0 S21603 17.5–22.0 5.0—7.0 7.5—9.0 0.25—0.50 0.03 max. 0.030 max. Mo 2.0—3.0 S24000 17.0–19.0 2.25—3.75 11.5—14.5 0.20—0.40 0.08 max. 0.030 max. EN*** Cr Ni Mn N C S Others 1.4371 16.0–17.0 3.5—5.5 6.0—8.0 0.15—0.20 0.03 max. 0.015 max. 1.4372 16.0–18.0 3.5—5.5 5.5—7.5 0.05—0.25 0.15 max. 0.015 max. 1.4373 17.0–19.0 4.0—6.0 7.5—10.5 0.05—0.25 0.15 max. 0.030 max.

*AISI = American Iron and Steel Institute designations **UNS = Unified Numbering System designations ***EN = EN 10 088-2 designations

4 Austenitic Chromium-Manganese Stainless Steels – A European Approach

3 The new 200 European grade: 1.4618

While technical development determines Table 2. Chemical composition and me- a material’s potential, economic factors chanical properties of 1.4618

often decide its market success. The most Steel number 1.4618 relevant economic factor over the last ten Steel name X9CrMnNiCu17–8–5–2 years has been the volatility of raw-material Chemical composition C <0.10, Si <1.00, prices – especially that of nickel. In appli- (% by mass) Mn 5.50–9.50, P <0.070, S <0.010, Cr 16.50–18.50, cations with strong inter-material compe- Ni 4.50–5.50, Cu 1.00–2.50, tition, where several materials can qualify N <0.15 for the same end-use, price factors usually Rp0.2 (MPa) min. 220 tip the balance. Rm (MPa) 520–850

A80 (%) min. 40 In the case of the 200-series grades, de- KV (J) min. 100 signed to substitute the classical 300 series (grades mainly characterized by good The new grade 1.4618 also falls within the corrosion resistance, low yield strength analysis band of grade 201. However, it is and high formability properties), the mar- distinct from grade 1.4372 in three respects: ket lacked a well defined, standardised • It is on the “rich side” of the 201 composi- offer. Most of the developed grades were tion band, which is beneficial to its corro- under alloyed, when considering general or sion resistance. localized corrosion resistance, or suffered • It is low in allowable sulphur content, from increased sensitivity to delayed crack- which further improves corrosion resist- ing and stress corrosion cracking. ance. • Copper is added for metallurgical rea- The newly-developed austenitic CrMn sons, to obtain mechanical properties grade (with 16.5 % Cr min.; 4.5 % Ni min.) close to those of grade 1.4301 (304) in is designed to obtain an optimum compro- terms of elongation to rupture. However, mise between cost reduction (lower nickel), the yield strength of the 200 series is high formability and the achieving of corro- higher than that of the 300 series. sion resistance as close as possible to that of 1.4301. Improvements in melting practic- Being new, the grade is not yet included es have made it possible to reduce carbon in standard EN 10088–1:2005. Until the content and add nitrogen, which improves next revision of EN 10088–1, certificates formability. Drawability is further increased can be supplied by the mills according to by copper alloying. ASTM A 240 grade 201 and the agreement of the customer on copper content. Table 2 shows the 1.4618 specification, agreed by European stainless steel producers. The grade meets the “rich side” of the AISI 201 specification and is further alloyed with copper.

5 4 Mechanical properties 6 Austenitic Chro mium-Manganese Stainless Stee ls – A European Approach

Rp0,2, Rm (MPa) 1600 1000 1400 1200 800 600 400 200 Table although Mechanical of grade 1.4301 (304). Figure 3. Mechanical properties versus cold deformation for 1.4307/304L (left) and 1.4618 (right) (304L) andmuch softerthan 1.4372 (201). 1.4618 is similar to 1.4301 (304)and1.4307 show that interms of mechanical properties, ternative to 1.4301 or1.4307. Figures 4and5 sometimes considered as alower-cost al- In certain environments, grade 1.4618 is state than 1.4307 (304L). er mechanical properties inthecold worked of strength (R 1.4310 R , R (MPa)

p0,2 m 1.4618. 01 1600 1000 1400 1200 800 600 400 200 2 (301) 01 shows 02 grade c Grade old deformation(%) A R p0.2

m 80 properties 02 austenitic 1.4 03

typical ) c 30 old deformation(%) A R 1.4618 is m 80 1.4618 7 /30 1.4 03

04 slightly 30

4L mechanical 7 /30 R

04 05 p0,2 shows grade remain behaves

4L higher R 05 p0,2 06

– slightly very i.e.

similarly 06

0 properties 0 20 20 30 40 50 60 70 than

its

similar,

80 80 (%) A 0

high- yield 0 20 20 30 40 50 60 70 that

80 80 (%) A

very formability tion than CrNi austenitic grade 1.4307. sensitive to martensitic phase transforma- cold R Figure 4 shows that 1.4618 has much lower

Rp0,2, Rm (MPa) p0.2 1600 1000 1400 1200 800 600 400 200

andR stable

Rp0,2, Rm (MPa) deformed, 01 1600 1000 1400 1200 800 600 400 200

is 01 austenitic m 02

than 1.4372 (201)andthat improved. c A R old deformation(%) m 80 02 03 alloy c 1.461 A R old deformation(%) m 80

03 04 structure,

8 1.4618 Furthermore, 1.461 R 04 05 p0,2 8 R 05 p0,2 06 exhibits being 06 0 when 0 20 20 30 40 50 60 70 less

80 80 (%) 0 A a

0 20 20 30 40 50 60 70

80 80 (%) A Austenitic Chromium-Manganese Stainless Steels – A European Approach

Figure 4. Comparison of the mechanical properties of several austenitic stainless steels at room temperature (2B, 3 mm)

One of the factors determining the form- Typical room temperature and sub-zero ability of a steel grade is its alloying com- temperature mechanical properties are pre- position. The characteristics affecting the sented for 1.4372, for general information. formability of stainless steel include yield Tensile strength increases substantially strength, tensile strength, ductility and the with decreasing temperature and this ef- effect of work hardening on these proper- fect can also be found with chromium-nickel ties. The yield strength of 1.4618 is modest austenitic stainless steels. Yield strength and only slightly higher than that of auste- also increases, but to a lesser extent. nitic CrNi grades. The drawing ratio, however, is comparable to that of austenitic Some reduction in ductility can be observed, CrNi grades. as measured by elongation. However, ductility values remain high down to –100 °C.

1600 80 1400 70

1200 A5 60 1000 50 A 5 (MPa) (%) m 800 40 Rm , R

p0,2 600 30 R

400 Rp0,2 20 200 10 Figure 5. Mechanical properties at sub-zero 0 0 temperatures for 1.4372 -120 -100 -80 -60 -40-20 02040 (N = 20, thickness 2 mm, Ni 3.6–4.5 %, T (°C) C 0.03–0.06 %)

7 Austenitic Chromium-Manganese Stainless Steels – A European Approach

Figure 6. Mechanical 800 80 properties at elevated temperatures for 1.4372 700 70 (N = 20, thickness Rm

2 mm, Ni 3.6–4.5 %, 600 A5 60 C 0.03–0.06 %) 500 50 A 5 (MPa) (%) m 400 40 , R

Rp0,2

p0,2 300 30 R 200 20 100 10 0 0 020406080 100 120 T (°C)

For some applications, the effect of sub- Like all austenitic stainless steel, 1.4618 has zero temperatures must also be considered exceptional toughness and does not exhibit in materials selection. Austenitic stain- the ductile to brittle transition temperature less steels are very often used in sub-zero (DBTT) behaviour that characterises ferritic temperature applications. It is important and martensitic stainless steels. The varia- for safe service that a high level of fracture tion of impact toughness with temperature toughness is maintained at all exposure is therefore minor and the steel can be suc- temperatures. cessfully used at sub-zero temperatures. Figure 7 shows impact toughness results at different temperatures.

1D, 5 mm Figure 7. Impact tough- 400 2D, 3 mm ness results for steel 350

grade 1.4618 (1D – hot )

2 300 rolled, annealed and m 250 pickled, 2D – cold rolled,

annealed and pickled) V ( J/c 200

KC 150 100 50 -60 -40-20 0204060 T ( °C )

8 Austenitic Chromium-Manganese Stainless Steels – A European Approach

5 Formability

Austenitic stainless steels are almost with- nickel and copper content improves drawa- out exception well suited to deep-drawing bility. This is also why 1.4618 performs very operations. The most important properties well in terms of formability. affecting drawability are yield strength, tensile strength and ductility. Composition is another important factor. In general, higher

ø ø 1 1 6 6 R 4 2 4 2 5 5 1 6 5 8 3

6 3 1 3 R R Figure 8. Stretchforming 4 (left) and drawing 3 1 - Punch 9 2 - Punch support 4 process (right) 3 - Die 7 4 - Hold-down ring 5 - Blank 5 - Hold-down ring 6 - Part 1 - Punch 6 - Hold-down ring support 2 - Punch support 7 - Ejector plate 3 - Die 8 - Blank 4 - Die support 9 - Part

Figure 9. Erichsen test sample (left) and swift cup test samples (right)

D Expansion - Erichsen (mm) Limit Drawing Ratio - LDR = d

Figure 10. Comparison of formability

9 diagram (thickness 1 mm) Figure 12. Forming limit between 1.8 and 2. stainless steels are Typical LDR values for (LDR) = D/d. The Limit Drawing Ratio Figure 11. 10 Austenitic Chro mium-Manganese Stainless Stee ls – A European Approach nitrogen of minimum1%Cu additions andoptimum classic 1.4372 (201)grade. The combination LDR values are improved compared with the grades. grade 1.4618 compared to other200series improves True major strain -0 ,3

content the -0,2 1.4 formability

301 obviously -0,1

properties

0, 0, 0, 0, 0, 0,6 significantly 1.4 1 3 5 2 4 372 (4, 0 T rue minorstrain

5 %Ni) of

0, representation the forming limitis curve, adirect anduseful The forming limit diagram, also known as produce failure. ray To construct aforming limit diagram, anar tions of strain that 1.4618 can withstand. low this encompasses curve all thecombina - that can occur without failure. The area be- illustrates thebiaxial combination of strain curve strain at each location. The forming limit nal gridto determine themajor andminor are thencompared with thecircles of origi- The major andminoraxes of theellipses except inareas of pure biaxial deformation. come ellipses wherever deformation occurs, before forming. The individual circles be- imprinted onthesurface of thesheet metal 1

is circles,

defined 0, 20 1.4618 (4, often of by

formability.

strain 2.5 5 %Ni,2, ,3 mm combinations in 0, 5 %Cu The diameter, 4 diagram )

that 0, is 5 -

Austenitic Chromium-Manganese Stainless Steels – A European Approach

Delayed cracking is reduced by the chemical (small crevices, pits, etc.). This is consist- composition of 1.4618. The grade performs ent with results presented earlier that show almost like grade 1.4301 (AISI 304). Salt a slight decrease in localised corrosion re- spray tests performed on cups have shown, sistance when comparing grade 1.4618 with in the most critical areas, crack propaga- grade 1.4301 (304). tions for grade 1.4618 that are not observed for type 1.4301 (AISI 304) grades. Metallo- graphic investigations have identified that cracks mostly initiate in corroded areas

Table 3. Sensitivity to delayed cracking of some austenitic steels as a function of the deep drawing ratio, measured in Swift cup tests

Swift cup test / Deep drawing ratio Grade Ni (%) Cu (%) 1.4 1.6 1.8 2.0 2.12 2.14 1.4301 8.1 0.5 + + + + + + 1.4618 4.7 2.4 + + + + + 1.4372 4.4 0.3 + + + ------1.4372 3.6 0.3 + + ------“204Cu” 1.1 1.7 + ------+ = Successful -- = Delayed cracking

11 corrosion resistance correlation with pitting corrosion resistance in sembly. Right: crevice steel part after disas- corrosion on a stainless Figure 14. Left: crevice potential, pH 7). erties (critical pitting rosion resistance prop- Figure 13. Pitting cor- 6 Corrosion resistance properties 12 Austenitic Chro mium-Manganese Stainless Stee ls – A European Approach 0.02 tiodynamic-curve 1.4618 The pitting corrosion resistance of grade its pitting corrosion resistance being better The grade behaves like grade 1.4310 (301), Resistance to crevice initiation Vpit (mV/SCE) pHd M 300 200 400 500 600 70 800 NaCl 0 has 10 4, 2, 3, 2, 1, 3, 1,

(23 0 5 0 0 0 5 5 been 1.4512 (409) 14 °C, tests pH investigated 12 15 1.4 7) 1.4016/4 1.4510/4

372/20 solution 16 performed 1.461 Cr (%) 1 30 39 14 8 17 (Figure 1.4 by 318

1.4 poten- 18 301/30 in PREN (%Cr 1.4016 (4 16 13). 1.4509 (441) a 4

19 1.4 1.4510 (4 372 (201) than which enhance pitting corrosion resistance. in (304L). This is theresult of aslight reduction lower than that of austenitic grade 1.4307 30) 18 +3, Cr 1.4 that content,

Propagation rate (µA/pH) 3 %Mo+16N) 1000 39) 301 (3 100 1.461 10

1 1 of 20

8 0, 04 classical 11 partially 1.4510/4 1.4016/4 ) 1.4526 (4 1.440 39 30

201 22

offset 36) 4 (316L) Ni (%) grade

by 1.4521 (444) 1.4

1.461 24 N but 1.4 372/20 additions, 318/301LN 1.4

8 301/30 slightly 1 26 4 10

Austenitic Chromium-Manganese Stainless Steels – A European Approach

The crevice corrosion resistance (crevice ini- best-performing grade among the 200 se- tiation) of grade 1.4618 is significantly bet- ries grades investigated. ter than that of other 200 series grades. It is equivalent to that of 1.4310 (301) and very Intergranular corrosion resistance was close to grade 1.4307 (304L). investigated by means of EN ISO 3651-2 (Strauss tests). Reducing nitrogen and car- With crevice corrosion, Ni has a power- bon content improves the steel’s behaviour. ful effect in reducing its propagation. With Only sensitising treatments at 700 °C for 4.5 % Ni, grade 1.4618 is more resistant to 30 minutes followed by slow cooling induc- crevice corrosion than grades with lower es intergranular cracks, after Strauss test nickel content. For both pitting and crevice and bending operations. In these condi- corrosion resistance, grade 1.4618 is the tions, even grade 1.4301 (304) is sensitised.

Table 4. Intergranular corrosion testing conditions and results (Strauss test)

Grade EN ISO 3651-2 700 °C, 30 min + 650 °C, 10 min + 700 °C, 30 min + water cooling water cooling cooling 60o °C/h 1.4618 pass pass fail (0.05 % C, 4.5 % Ni) 1.4301 pass pass fail (0.05 % C, 8.1 % Ni) 1.4307 pass pass pass (0.02 % C, 8.1 % Ni) 1.4372 pass pass fail (0.05 % C, 4.5 % Ni)

Stress corrosion cracking was tested in salt spray (fog), in accordance with ASTM B 117. With stress corrosion cracking, the initiation and propagation of cracks under the combined action of tensile stresses and a corrosive environment is described.

Table 5. Stress corrosion cracking results after 1000 h of exposure, in a salt spray (fog) test, according to ASTM B 117

Number of cracks / Steel grade LDR Number of samples tested 1.83 0 / 3 1.4301 1.94 0 / 3 Figure 15. Stress corrosion cracking on the cup after 1.83 2 / 3 testing 1.4618 1.94 3 / 3

13 Austenitic Chromium-Manganese Stainless Steels – A European Approach

7 Physical properties

Physical properties important for the suc- Table 6. The coefficient of thermal expansion

cessful implementation of stainless steels Mean thermal expansion include coefficient of thermal expansion, EN ASTM coefficient between 20 °C and °C (10-6 K-1) electrical resistivity and specific heat. 200 400 1.4618 - 17.4 18.5 The coefficient of thermal expansion is the 1.4372 201 16.6 17.9 change in unit of length (or volume) accom- panying a unit change of temperature, at a 1.4301 304 17.0 18.5 specified temperature. Table 7. Electrical resistivity

The electrical resistivity properties of grade Electrical resistivity EN ASTM ( ·mm2/m) 1.4618 rank between those of 1.4372 and Ω 0 °C 25 °C 50 °C 100 °C 1.4301 austenitic alloys. 1.4618 - 0.76 0.77 0.79 0.85 1.4372 201 0.80 0.81 0.84 0.89 Specific heat is the quantity of heat required 1.4301 304 0.72 0.75 0.76 0.81 to change by one degree the temperature of a body of material of unit mass. Specific heat Table 8. Specific heat values for selected austenitic stainless steels Specific heat are given in Table 8. EN ASTM (J/g·K) 39 - 41 °C 1.4618 - 0.51 1.4372 201 0.51 1.4301 304 0.48

14 Austenitic Chromium-Manganese Stainless Steels – A European Approach

8 Weldability

Table 9 shows typical welding conditions and in most cases the same welding filler for grade 1.4618. Grade 1.4618 behaves materials as for 1.4301 (304) or 1.4310 almost like grade 1.4301 (304). No specific (301) can be used. welding parameters need to be observed

Table 9. Typical 1.4618 welding conditions

Without filler With filler material material Welding Protective gas process Typical Filler metal Thickness thickness Wire rod Coil Spot welding <2mm Seam welding <2mm ER 308 L (Si) ER 308 L (Si) Ar GTAW / TIG <1.5 mm >0.5 mm 1.4370 1.4370 Ar + 5 % H2 ER 347 (Si) ER 347 (Si) Ar + He Ar ER 308 L (Si) Ar + 5 % H PAW / plasma <1.5 mm >0.5 mm ER 310 1.4370 2 Ar + He ER 347 (Si) Ar + 2 % CO2 Ar + 2 % O ER 308 L (Si) 2 Ar + He GMAW /MIG >0.8 mm 1.4370 Ar + 3 % CO + ER 347 (Si) 2 1 % H2 ER 308 L SAW >2 mm ER 347 (Si) E 308 Electrode repairs E 308 L E 347 He Restricted: Laser <5 mm Ar–N2

15 Austenitic Chromium-Manganese Stainless Steels – A European Approach

9 Summary

Extensive data on the newly-designed Grade 1.4618 is designed to offer end users 1.4618 grade has been presented. It is a grade that can replace grades similar to concluded that grade 1.4618, as a repre- 1.4301 (304) in numerous cases. The higher sentative of the 200 series, has an optimum carbon content than is present in 1.4307 chemical composition that makes it less (304L) restricts its use for thicker welded dependent on alloy-surcharge cost fluctua- sections. tions while obtaining mechanical and corrosion resistance properties similar to those The grade has been jointly developed by of grades 1.4301 (304) and 1.4310 (301). Acerinox, Aperam, Outokumpu and Thyssen- Krupp Stainless under the umbrella of Euro Good deep drawing properties can be ob- Inox. tained without significant sensitivity to delayed cracking. Although long-term experience is not available, initial experience indicates that grade 1.4618 has very similar weldability to grade 1.4301 (304). Weld- ing can be performed with the same filler material.

16 Austenitic Chromium-Manganese Stainless Steels – A European Approach

10 References

[1] New 200-series’ steels: an opportunity or a threat to the image of stainless steel?, Brussels: ISSF, 2005 [2] CHARLES, Jacques, “The new 200-series: an alternative answer to Ni surcharge?”, Proceedings of the Stainless Steel USA Int. Conf., Houston, 2006 [3] The Ferritic Solution, Brussels, ISSF, 2007 [4] CHARLES, Jacques, ‘’A new European 200 series standard to substitute 304 austenitics?’’, Proceedings, 6th European Stainless Steel Science and Market Conference, Helsinki, Jernkontoret, 2008, pp. 427-436 [5] TAULAVUORI, Tero, OHLINGSCHLÄGER, T., SÄYNÄJÄKANGAS, J.: ‘’A novel view on material selection of stainless steels by optimizing material costs and product properties’’, Proceedings, 6th European Stainless Steel Science and Market Conference, Helsinki, Jernkontoret, 2008, pp.335-341 [6] ASM Specialty Handbook, Stainless Steels, Davis, J.R. (ed.), ASM International, 1996

17 ISBN 978-2-87997-321-0

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