Martensitic Stainless Steel

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Martensitic stainless steel - Wikipedia

Martensitic stainless steel Stainless steels may be classified by their crystalline structure into four main types: austenitic, ferritic, martensitic, and duplex. Martensitic stainless steel is a specific type of stainless steel alloy that can be hardened and tempered through multiple ways of aging/heat treatment.[1][2][3][4]

Contents History Overview Chemical compositions

Tweezers made of 410 martensitic stainless steel

Mechanical Properties Physical properties Processing Applications [4] - corrosion resistant engineering steels (see above table on mechanical properties) used in a variety of mechanical engineering applications -wear resistant and corrosion resistant applications References

History In 1912, Harry Brearley of the Brown-Firth research laboratory in Sheffield, England, while seeking a corrosion-resistant alloy for gun barrels, discovered and subsequently industrialized a martensitic stainless steel alloy. The discovery was announced two years later in a January 1915 newspaper article in The New York Times.[5] Brearly applied for a U.S. patent during 1915. This was later marketed under the "Staybrite" brand by Firth Vickers in England and was used for the new entrance canopy for the Savoy Hotel in 1929 in London.[6] The characteristic body-centered tetragonal martensite microstructure was first observed by German microscopist Adolf Martens around 1890. In 1912, Elwood Haynes applied for a U.S. patent on a martensitic stainless steel alloy. This patent was not granted until 1919.[7]

Overview Martensitic stainless steels can be high- or low-carbon steels built around the composition of iron, 12% up to 17% chromium, carbon from 0.10% (Type 410) up to 1.2% (Type 440C):[8] Up to about 0.4%C they are used mostly for their mechanical properties ( pumps, valves, shafts ..). Above, 0.4% they are used mostly for their wear resistance (cutlery surgical blades, plastic injection molds, nozzles...). They may contain some Ni (Type 431) which allows a higher Cr and/or Mo content, thereby improving corrosion resistance and as the Carbon content is also lower, the toughness is improved. Grade EN 1.4313 (CA6NM) with a low C, 13%Cr and 4%Ni offers good mechanical properties, good castability, good weldability and good resistance to cavitation. It is used for nearly all the hydroelectric turbines in the world, including those of the huge "Three Gorges " dam in China. Additions of B, Co, Nb, Ti improve the high temperature properties, particularly creep resistance (for heat exchangers in steam turbines). A specific grade is Type 630 (also called 17/4 PH) which is martensitic and hardens by precipitation at 475 °C.

Chemical compositions

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Martensitic stainless steel - Wikipedia Chemical composition of a few common martensitic stainless steel grades from EN 10088-1 (2005) standard

Chemical composition (main alloying elements) in wt% EN

EN

AISI

Steel designation

Number

Number

Number

C

Cr

Mo

Others

Remarks

X12Cr13

1.4006

410

0.12

12.5

—

—

Base grade, used as stainless engineering steel

X20Cr13

1.4021

420

0.20

13.0

—

—

Base grade, used as stainless engineering steel

X50CrMoV15

1.4116

-

0.50

14.5

0.65

V: 0.15

Used chiefly for professional knives

X14CrMoS17

1.4104

430F

0.14

16.5

0.40

S: 0.25

Sulphur improves machinability

X39CrMo17-1

1.4122

-

0.40

16.5

1.10

—

Used chiefly for professional knives

X105CrMo17

1.4125

440C

1.10

17.0

0.60

—

Tool steel grade (440C), high wear resistance

X17CrNi16-2

1.4057

431

0.17

16.0

—

Ni: 2.00

Ni replaces some C for higher ductility & toughness

X4CrNiMo16-5-1

1.4418

-

≤ 0.06

16.0

1.10

Ni: 2.00

Highest corrosion resistance of martensitics

Ni: 4.00 X5CrNiCuNb16-4

1.4542

≤ 0.07

630 (17/4PH)

16.0

-

Precipitation hardening grade

Cu: 4.00

High strength. Used in aerospace

Nb: 5xC to 0.45 There are many proprietary grades not listed in the standards, particularly for cutlery.

Mechanical Properties They are hardenable by heat treatment (specifically by quenching and stress relieving, or by quenching and tempering (referred to as QT).[9][10] The alloy composition, and the high cooling rate of quenching enable the formation of martensite. Untempered martensite is low in toughness and therefore brittle.Tempered martensite gives steel good hardness and high toughness as can be see below; used largely for medical tools (scalpels, razors and internal clamps).[11] Mechanical properties of a few common martensitic stainless steel grades according to EN 10088-3 Standard Mininmum Yield stress, MPa

Tensile strength, MPa

Minimum Elongation, %

Heat treatment

1.4006

450

650 - 850

15

QT650

1.4021

600

650 - 850

12

QT800

1.4122

550

750 - 950

12

QT750

1.4057

700

900 - 1050

12

QT900

1.4418

700

840 - 1100

16

QT900

1.4542

790

960 - 1160

12

P960

IN the heat treatment column, QT refers to Quenched and Tempered, P refers to Precipitation hardened

Physical properties Physical properties of a few common martensitic stainless steels from EN 10088-1 (2005) standard Young’s Modulus at 20 °C,

Mean coefficient of thermal expansion between 20 and 100 °C

Gpa

10−6K−1.

Thermal Conductivity at 20 °C

Specific Thermal capacity at 20 °C

W.m−1K−1

J.Kg−1.K−1

10.5

30

460

0.60

215

10.5

30

460

0.65

215

10.5

30

460

0.65

215

10.4

15

430

0.80

440C

215

10.4

15

430

0.80

431

215

10.0

25

460

0.70

200

10.5

25

430

0.60

195

10.3

30

430

0.80

200

10.9

30

500

0.71

EN Designation

EN

X12Cr13

1.4006

410

215

X20Cr13

1.4021

420

X50CrMoV15

1.4116

X39CrMo17-1

1.4122

X105CrMo17

1.4125

X17CrNi16-2

1.4057

X3CrNiMo13-4

1.4313

X4CrNiMo16-51

1.4418

X5CrNiCuNb164

1.4542

AISI

630

https://en.wikipedia.org/wiki/Martensitic_stainless_steel

Electrical resitivity

10−6Ω.m

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Martensitic stainless steel - Wikipedia

Processing When formability, softness, etc. are required in fabrication, steel having 0.12 per cent maximum carbon is often used in soft condition. With increasing carbon, it is possible by hardening and tempering to obtain tensile strength in the range of 600 to 900 N/mm2, combined with reasonable toughness and ductility. In this condition, these steels find many useful general applications where mild corrosion resistance is required. Also, with the higher carbon range in the hardened and lightly tempered condition, tensile strength of about 1600 N/mm2 may be developed with lowered ductility. A common example of a Martensitic stainless steel is X46Cr13. Martensitic stainless steel can be nondestructively tested using the magnetic particle inspection method, unlike austenitic stainless steel.

Applications [4] Martensitic stainless steels, depending upon their carbon content can be seen as

- corrosion resistant engineering steels (see above table on mechanical properties) used in a variety of mechanical engineering applications pumps valves boat shafts

-wear resistant and corrosion resistant applications cutlery medical tools (scalpels, razors and internal clamps)[11] bearings (ball bearings) razor blades injection molds for polymers brake disks for bikes & motorbikes

References 1. "Premium Alloys 17-4 Stainless Steel" (https://premiumalloys.com/17_4_ ph.html). Retrieved 2019-11-26. 2. "Classifications of Stainless Steel" (https://app.aws.org/wj/1998/11/koteck i/). aws.org. American Welding Society. Retrieved 2019-04-02. 3. D. Peckner and I.M. Berstein (1977). Handbook of stainless steels. Mc Graw Hill. pp. Chapter 6. ISBN 978-0070491472. 4. "Martensitic Stainless Steels" (https://www.worldstainless.org/about-stainl ess/what-is-stainless-steel/categories-grades-and-product-forms/). International Stainless Steel Forum. 2018. 5. "A non-rusting steel". New York Times. 31 January 1915. 6. Sheffield Steel, ISBN 0-7509-2856-5. 7. Rodney Carlisle; Scientific American (2005-01-28). Scientific American Inventions and Discoveries: All the Milestones in Ingenuity – From the Discovery of Fire to the Invention of the Microwave Oven (https://books.g oogle.com/books?id=pDbQVE3IdTcC&pg=PA380). John Wiley & Sons. p. 380. ISBN 978-0-471-66024-8.

8. http://metals.about.com/od/properties/a/Steel-Types-And-Properties.htm, http://www.totalmateria.com/page.aspx? ID=CheckArticle&site=kts&NM=199. 9. Dossett, Jon L; Totten, George E., eds. (2014). Heat treating of irons and steels (https://dl.asminternational.org/handbooks/book/9/Heat-Treating-of -Irons-and-Steels). ASM International. pp. 382–396. ISBN 978-1-62708168-9. 10. Budynas, Richard G. and Nisbett, J. Keith (2008). Shigley's Mechanical Engineering Design, Eight Edition. New York, NY: McGraw-Hill Higher Education. ISBN 978-0-07-312193-2. 11. Akhavan Tabatabae, Behnam; et al. (2009). "Influence of Retained Austenite on the Mechanical Properties of Low Carbon Martensitic Stainless Steel Castings" (https://doi.org/10.2355/isijinternational.51.471). ISIJ International. 51 (3): 471–475. doi:10.2355/isijinternational.51.471 (https://doi.org/10.2355%2 Fisijinternational.51.471).

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