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Page 1: Pengelasan Baja Tahan Karat (baru)

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Pengelasan Baja Tahan Karat

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Baja Tahan Karat

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Apa itu baja tahan karat (stainless steels)

•  SS defined as Iron‐base alloy containing > 10.5% Cr & < 1.5%C and they 

are considered

 high

 alloy

•   used for corrosion and heat resistant applications especially in saline solutions, under oxidizing 

conditions. 

•   Corrosion resistance is imparted by the formation of  a passivation layer characterized by:

•   Insoluble chromium oxide film on the surface of  the metal ‐ (Cr2O3) . 

•   Develops when

 exposed

 to

 oxygen

 and

 impervious

 to

 water

 and

 air.

•   Layer is too thin to be visible

•   Quickly reforms when damaged

•   Susceptible to sensitization, pitting, crevice corrosion and acidic environments.

•   Passivation can be improved by adding nickel, molybdenum and vanadium.

•   In general

 a minimum

 concentration

 of 

 12%

 Cr

 is

 required

 to

 obtain

 a film

 that

 completely

 

covers the exposed surface of  a sample.

•   The Cr2O3 in the steel is very stable against attack by a number of  chemicals and electrolytic 

corrosion actions.

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•  Over 150 grades of  SS available, usually categorized into 5 series 

containing alloys

 w/

 similar

 properties.

•  All SS types 

•  Weldable by virtually all welding processes

•  Process selection often dictated by available equipment

•   Simplest &

 most

 universal

 welding

 process•   Manual SMAW with coated electrodes

•   Applied to material > 1.2 mm

•   Other very commonly used arc welding processes for SS

•   GTAW, GMAW, SAW & FCAW

•  Optimal 

filler 

metal 

(FM)•   Does not often closely match base metal composition

•   Most successful procedures for one family 

•   Often markedly different for another family

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• SS base metal & welding FM chosen based on•  Adequate corrosion resistance for intended use

• Welding FM

 must

 match/over

‐match

 BM

 content

 w.r.t

•  Alloying elements, e.g. Cr, Ni & Mo

•  Avoidance of  cracking

• Unifying theme in FM selection & procedure 

development•  Hot cracking

•  At temperatures < bulk solidus temperature of  alloy(s)

•  Cold cracking

•  At rather

 low

 temperatures, typically

 < 150

 ºC

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•Hot 

cracking•  As large Weld Metal (WM) cracks

• Usually 

along 

weld 

centreline•  As small, short cracks (microfissures) in WM/HAZ

• At fusion line & usually perpendicular to it•  Main concern in  Austenitic  WMs

•  Common remedy

• Use mostly austenitic  FM with small amount of  ferrite•   Not suitable when requirement is for

•   Low magnetic permeability

•   High toughness at cryogenic temperatures

•   Resistance to

 media

 that

 selectively

 attack ferrite

 (e.g.

 urea)

•   PWHT that can embrittle ferrite

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•  Cold 

cracking•  Due to interaction of  

•  High welding stresses

•  High‐strength metal

•  Diffusible hydrogen

•  Commonly occurs in Martensitic  WMs/HAZs

•  Can occur in Ferritic  SS weldments embrittled by

•  Grain coarsening and/or second‐phase particles

•  Remedy•  Use of  mostly austenitic FM (with 

appropriate 

corrosion 

resistance)

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Castro & Cadenet, Welding Metallurgy of

Stainless and Heat-resisting Steels

Cambridge University Press, 1974

A=Martensitic Alloys

B=Semi-Ferritic

C=Ferritic

12% Cr raises the critical 

temperatures and reduces the 

austenite region. 

With sufficient amounts of  carbon, 

these steels

 can

 be

 heat

 treated

 to

 a 

martensitic structure.

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General Properties

 of 

 Stainless

 Steels

•  Electrical 

Resistivity

•   Surface & bulk resistance is 

higher than that for plain‐

carbon steels

•  Thermal Conductivity

•   About 40 to 50 percent that of  plain‐carbon steel

•  Melting 

Temperature

•   Plain‐carbon:1480‐1540 °C

•  Martensitic:  1400‐1530 °C

•  Ferritic:  1400‐1530 °C

•   Austenitic:  1370‐1450 °C

•  Coefficient 

of  

Thermal 

Expansion

•   Greater coefficient than plain‐

carbon steels

•  High Strength

•   Exhibit high strength at room 

and elevated temperatures

•  Surface 

Preparation•  Surface films must be 

removed prior to welding

•  Spot 

Spacing

•   Less shunting

 is

 observed

 than

 

plain‐carbon steels

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Grades

 

of

 

Stainless

 

Steel

•  To make

 a steel

 "stainless"

 it

 needs

 to

 contain

 a minimum

 of 

 12%

 Chromium (Cr). 

•  The problem with 12% Cr is that it is fairly brittle and only provides the 

minimum corrosion resistance. Increasing the Chromium content to 17% 

improves corrosion resistance but increases brittleness. Adding 8% Nickel 

makes the

 steel

 ductile

 again.

 Thus

 18/8

 stainless

 was

 born

 (304).

 316

 / 316L has additional Molybdenum and higher Nickel which provides greater 

corrosion resistance.

•  With stainless when you see two numbers they always refer to the 

Chromium and Nickel content ‐ 18/8 is 18%Cr and 8%Ni. If  you see three

numbers like 19/12/3

 they

 refer

 to

 the

 Chromium,

 Nickel

 and

 Molybdenum

 

content. 316L is 19%Cr, 12%Ni and 3%Mo.

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Jenis baja tahan karat

In general, there are five types of stainless steels based on their crystal

structure and strengthening mechanisms. They are (AISI classes for SS ):

1. Austenitic stainless steels

 – 200 series = chromium, nickel, manganese (austenitic)

 – 300 series = chromium, nickel (austenitic)

2. Ferritic stainless steels

• 400 series = chromium only (ferritic)

3. Martensitic stainless steels

 – 500 series = low chromium <12% (martensitic)

4. Precipitation-hardened stainless steels – 600 series = Precipitation hardened series (17-7PH, 17-7 PH, 15-5PH)

5. Duplex stainless steels

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Aplikasi

•  Food industry

 (cookware,

 flatware,

 food

 transport

 and

 storage

 tankers) due to its corrosion resistance and antibacterial properties.

•  Surgical equipment

•  Aerospace

•  High end automotive, industrial, etc.

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Austenitic SS

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 Fe

 

18 Cr

 

8 Ni)

 

C Phase

 

Diagram

 

Baja

 

Tahan Karat

 

Austenitik)

• Nickel stabilizes the austenite,  –phase instainless steels (SS).

• When 8% Ni is added to an 18% Cr steel – 

18/8 SS – the -phase is stable down to room

temperature at very low C – the three phase (+ + carbide) eutectoid region is at lower

temperatures.

• The high temperature -ferrite is also very

restricted.(  + + carbide) eutectoid

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Characteristics of 

 Austenitic

 Stainless

 

steels

• Chrome-nickel or chrome -nickel- manganese alloys Austenitic, non magnetic and donot harden by heat treatment.

• Total content of nickel and chromium is at least 23%• Difficult to machine. Can be improved by Selenium of sulfur additions.• Best high temperature strength and reistance to scaling. Hence the best corrosion

resistance.

• Cold working causes work hardening.• Can be hot worked easily.• Type 302 stainless steel is more used.(austenitic). Modified into 22 different alloys.• Lowering the carbon to 0.08% gives stainless steel type 304 with improved weldability.

Used for most fabrication that needs welding.

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The

 

200/300

 

Series

 

of

 

Austenitic

 

Stainless

 

Steels

• These alloys are based on a minimum of 18% Cr – 8% Ni with a maximum of 0.15C. Most common SS (roughly

70% of total SS production).Contain between 16 and 25 percent chromium, plus sufficient amount of nickel,

manganese and/or nitrogen.

• Have a face-centered-cubic (fcc) structure, Nonmagnetic, Good toughness, Spot weldable, Strengthening can be

accomplished by cold work or by solid-solution strengthening

• General use where corrosion resistance is needed. Used for flatware, cookware, architecture, automotive,

etc. Typical alloy 18% Cr and 10% Ni = commonly known as 18/10 stainless. Also have low carbon version of

Austenitic SS (316L or 304L) used to avoid corrosion problem caused by welding, L = carbon content < 0.03%

• 20% Cr – 10% Ni have better properties for higher specifications such as very low carbon grade (L), eg., < 0.03% C is

 prevents the formation of (CrFe)4C at grain boundaries, which depletes the Cr below 12% in the bulk.

• Addition of 2-3% Mo enhances corrosion protection in neutral salt solutions. As well, very low carbon grade < 0.03% C

is required for welded components

• Addition of Ti (5xC) or Nb (10 x C), enables carbon to be increased to 0.08% for welded products by forming TiC or

 NbC instead of (FeCr)4C.

• Austenitic, High strength, best corrosion resistance. High temp capability up to 1200 F. non-magnetic,

good ductility and toughness, not hardenable by heat treatment, but they can be strengthened via cold

working, best corrosion resistance but most expensive, corrosive in hydrochloric acid.

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Typical Microstructure of 300 series of Austenitic Stainless Steels

Microstructures of 302 Stainless Steel containing 18Cr – 8Ni – 0.11C

Quenched from 985 oC

Austenite + annealing twins

(boundaries are lines) plus

undissolved carbides

(mag – 1000x)

Quenched from 1205 oC

Course Austenite + annealing

twins and no undissolved carbides

(mag – 1000x)

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200/300 Series SS (Austenitic):

• Most common

 SS

 (roughly

 70%

 of 

 total

 SS

 production)

• Used for flatware, cookware, architecture, automotive, etc.

• 0.15% C (max), 16% Cr (min) and Ni or Manganese

• Austenitic, High strength, best corrosion resistance.  High temp capability up to 

1200 F. non‐magnetic, good ductility and toughness, not hardenable by heat treatment,

 but

 they

 can

 be

 strengthened

 via

 cold

 working,

 best

 corrosion

 

resistance but most expensive, corrosive in hydrochloric acid. 

• General use where corrosion resistance is needed.

• Typical alloy 18% Cr and 10% Ni = commonly known as 18/10 stainless

• Also have

 low

 carbon

 version

 of 

 Austenitic

 SS

 (316L

 or

 304L)

 used

 to

 avoid

 corrosion problem caused by welding, L = carbon content < 0.03%

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•300 Series—austenitic chromium‐nickel alloys 

Type 301—highly ductile, for formed products. Also hardens rapidly during mechanical working. Good weldability. 

Better wear resistance and fatigue strength than 304. 

Type 302—same

 corrosion

 resistance

 as

 304,

 with

 slightly

 higher

 strength

 due

 to

 additional

 carbon.

 

Type 303—free machining version of  304 via addition of  sulfur and phosphorus. Also referred to as "A1" in accordance 

with ISO 3506.[10]

Type 304—the most common grade; the classic 18/8 stainless steel. Also referred to as "A2" in accordance with ISO 

3506.[10]

Type 304L— same as the 304 grade but contains less carbon to increase weldability. Is slightly weaker than 304. 

Type 304LN—same as 304L, but also nitrogen is added to obtain a much higher yield and tensile strength than 304L. 

Type 308—used

 as

 the

 filler

 metal

 when

 welding

 304

 

Type 309—better temperature resistance than 304, also sometimes used as filler metal when welding dissimilar steels, 

along with inconel. 

Type 316—the second most common grade (after 304); for food and surgical stainless steel uses; alloy addition of  

molybdenum prevents specific forms of  corrosion. It is also known as marine grade stainless steel due to its increased 

resistance to chloride corrosion compared to type 304. 316 is often used for building nuclear reprocessing plants. 316L 

is an extra low carbon grade of  316, generally used in stainless steel watches and marine applications due to its high 

resistance to corrosion. Also referred to as "A4" in accordance with ISO 3506.[10] 316Ti includes titanium for heat 

resistance, therefore it is used in flexible chimney liners. 

Type 321—similar to 304 but lower risk of  weld decay due to addition of  titanium. See also 347 with addition of  

niobium for desensitization during welding. 

Common 300 series grades of SS:

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Carbide

 

Phases

 

in

 

Stainless

 

Steels

• There are three Fe-Cr carbides phases

formed in slowly cooled stainless steels as a

function of carbon and chromium content.1. Up to 15%, Cr can enter cementite without

changing its structure, to form (FeCr)3C, which

is the carbide present in low alloy steels.

2. The next carbide is (FeCr)7C3, which contains a

minimum of 35% Cr. This is the carbide formedin high-carbon high-chromium tool steels.

3. (FeCr)4C, which contains > 70% Cr, is the

carbide normally found in stainless steels.

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Carbide

 

Precipitation

 

at

 

Grain

 

Boundaries

• The precipitation of (CrFe)4C, which contains 70 % Cr, at grain boundaries

causes the concentration of Cr in the adjacent austenite to fall below 12%,which degrades the corrosion resistance properties of the steel.

• The optimum temperature for precipitation of (CrFe)4C is around 650 oC,

which is attained in the heat affected zone adjacent to a fusion weld.

• Stainless steels with carbon as low as 0.15% can thus suffer “weld decay”.

• It can be eliminated by

1) lowering carbon to 0.03%, or

2) use Ti or Nb to remove the carbon as TiC or NbC, without lowering the Cr content of

the austenite.

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Quenched from 1150 oCReheated 24 h at 650 oC

Carbides at grain boudaries

(low mag – 240x)

Quenched from 1150 oCReheated 24 h at 650 oC

Carbides at grain boundaries

(high mag – 1000x)

Precipitation

 

of

 

CrFe)

4

C

 

at

 

Grain

 

Boundaries

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Precipitation

 

of

 

CrFe)

4

C at

 

Grain

 

Boundaries

• The concentration profile of Cr in the matrix adjacent to a precipitate

of (CrFe)4C is given below.

• The Cr level falls from 18% to 7-8%, which is well below the 12%

limit for effective corrosion protection.

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Oxidation

 

Resistant

 

Stainless

 

Steels

• In order to maintain stability of the austenite phase the Cr was increased to 22 – 

26% Cr with Ni of 12 – 22%. The addition of Ni gives increased resistance to

oxidation at high temperatures. These steels are very expensive and only used for

special applications.

Micrograph of a welded joint in 20Cr – 12Ni

Stainless Steel, x50

• The structure of the original metal is

shown on the left.

• The fine-grained dark structure on the

right is the weld material (filler).• In the centre where the metal has been

heated close to its melting point the

structure is largely austenitic with some

darker alloyed ferrite.

• In the heat affected zone, the austeniteshows pronounced grain growth and is

thus weaker than the original fine grained

structure.

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Ferritic SS

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Fe

 

Cr

 

Phase

 

Diagram

 

Baja

 

Tahan Karat

 

Jenis Feritik)

Cr is a ferritic stabilizer.

The austenite phase is thus condensed into a

small “ loop”, which extends out to 16% Cr

over the range of temperature 900 – 1400 oC.

At concentrations greater than 16% Cr, the  – 

Fe and -Fe phases are not distinguishable and

a common  –phase extends all the way to100% Cr.

The 50/50 composition orders at temperatures

 below ~900o

C to form the  –phase, whichcauses embrittlement in stainless steels.

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Pseudo

 

binary

 

Fe

 

– 12 Cr)

 

C

 

Phase

 

Diagram

• Carbon is soluble in Fe-Cr austenite and increases the Cr limit of the  –loop.

• Hardenable cutlery steels, which contain the minimum 12% Cr, are described in terms of a

 pseudo-binary (Fe + 12%Cr)-C phase diagram.

• The -field is severely constricted compared to the Fe-C diagram.

 – The maximum solubility of C is 0.7% and the eutectoid is at 0.35% C. – In addition, the eutectoid temperature (range) is raised to >800 oC.

Two forms of carbide are inequilibrium with the  –phase, ie., the

(CrFe)4C and (CrFe)7C3, depending

on the carbon content. eutectoid temperature (range)

 Note 12%Cr 

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Characteristics of 

 Ferritic Stainless

 

steels

• 14 to 27% Cr. Low in carbon but high in Cr compared to martensitic steels.

• Not hardened by heat treatment. Only moderately hardened by cold working• Can be cold or hot worked. Achieves maximum softness in annealed condition.• As annealed, their strength is 50% higher than plain carbon steels and corrosion

resistance and machinability is better than martensitic steels.• Annealing is done to relieve stresses due to welding or cold working.• Susceptible to embrittlement during slow cooling during annealing.

• Since martensite is not formed and since there is embrittlement possibility, thesesteels are not tempered.

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•400 common alloys 

Type 405— ferritic for welding applications 

Type 408—heat‐resistant; poor corrosion resistance; 11% chromium, 8% nickel. 

Type 409—cheapest

 type;

 used

 for

 automobile exhausts;

 ferritic (iron/chromium

 only).

 Type 410—martensitic (high‐strength iron/chromium). Wear‐resistant, but less corrosion‐resistant. 

Type 416—easy to machine due to additional sulfur 

Type 420—Cutlery Grade martensitic; similar to the Brearley's original rustless steel. Excellent 

polishability. 

Type 430—decorative, e.g., for automotive trim; ferritic. Good formability, but with reduced 

temperature and

 corrosion

 resistance.

 Type 440—a higher grade of  cutlery steel, with more carbon, allowing for much better edge 

retention when properly heat‐treated. It can be hardened to approximately Rockwell 58 hardness, 

making it one of  the hardest stainless steels. Due to its toughness and relatively low cost, most 

display‐only and replica swords or knives are made of  440 stainless. Also known as razor blade 

steel. Available in four grades: 440A, 440B, 440C, and the uncommon 440F (free machinable). 440A, 

having the

 least

 amount

 of 

 carbon

 in

 it,

 is

 the

 most

 stain

‐resistant;

 440C,

 having

 the

 most,

 is

 the

 strongest and is usually considered more desirable in knifemaking than 440A, except for diving or 

other salt‐water applications. 

Type 446—For elevated temperature service 

Common 400 series grades of SS:

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400 Series SS (Ferritic):

•   Ferritic, 

Automotive 

trim, 

chemical 

processing, 

blades, 

knives, 

springs, 

ball 

bearings, 

surgical instruments.  Can be heat treated!

•   Contain between 10.5% and 27% Cr, little Ni and usually molybdenum.

•   Common grades: 18Cr‐2Mo, 26Cr‐1Mo, 29Cr‐4Mo, and 29Cr‐4Mo‐2Ni

•   Magnetic (high in Fe content) and may rust due to iron content.

•   Lower strength vs 300 series austenitic grades

•   Cheap

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The

 

400

 

Series

 

of

 

Heat

 

Treatable

 

Stainless

 

Steels

 Martensitic  Stainless Steels)

• These steels are based on Martensite, 12-16% Cr with various amounts of Carbon.

• Low carbon grades containing up to 0.2 C containing up to 12-13% Cr are hardenable by air

quenching to form a low-carbon martensite (lath type) and are used for cutlery.• High carbon grades contain 0.6-1.2 C and 16-18 Cr form much harder high-carbon martensite

(lenticular type) on quenching and are used for surgical instruments.

Air cooled from 955 oC. Low

carbon martensite x1000

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The

 

400

 

Series

 

of

 

Heat

 

Treatable

 

Stainless

 

Steels

 erritic Stainless  Steels)

• Low carbon grades with up to 0.2 C and 14-18% Cr are ferritic and

can only be hardened by 1) cold work or 2) precipitation of carbide.

Air cooled from 790 oC ferrite plus carbide x1000

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Martensitic SS

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Characteristics of  Martensitic Stainless steels• Straight chromium steels with 11.5 to 18% Cr. C 0.15 Mn 1.25 Si 1• For turbine blades and corrosion resistant applications• Magnetic

• Can be machined (poorer machinability than plain carbon steels. Machinability can beimproved by adding small amounts of Selenium or Sulphur.)

• Hot working possible.• Can be hardened (by air cooling or oil quenching itself)

• Full hardness on air-cooling from ~ 1000 ºC• Softened by tempering at 500–750 ºC

• Maximum tempering temperature reduced If Ni content is significant• On high-temperature tempering at 650–750 ºC

• Hardness generally drops to < ~ RC 30• Useful for softening martensitic SS before welding for 

• Sufficient bulk material ductility

• Accommodating shrinkage stresses due to welding• Coarse Cr-carbides produced

• Damages corrosion resistance of metal• To restore corrosion resistance after welding necessary to

• Austenitise + air cool to RT + temper at < 450 ºC

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500 Series SS (Martensitic):

•   Not as corrosion resistant as the other classes but extremely strong and tough as well as 

machineable and

 can

 be

 hardened

 via

 heat

 treat.

•   High strength structural applications (Su up to 300 ksi)  – nuclear plants, ships, steel turbine blades, tools, etc.

•   Magnetic

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PH SS

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Precipitation

 

Hardened

 

Ferritic Stainless

 

Steels

• Ferritic stainless steels with ~17% Cr have very low carbon of  0.04  – 0.07 C, which give 

good corrosion resistance and high strength.

• The 17  – 4 PH* (with 4% Ni) alloy is transformed to low carbon martensite (lath 

martensite) on cooling from austenite and is hardened by ageing at 480 

oC due to the 

precipitation of  Al‐Ti and a Nb‐Cu compound.

• The 17‐7PH ( with 7% Ni) alloy is semi‐austenitic and requires a more complicated series of  

treatments to produce a precipitation‐hardened martensite.

• 5% ‐ 20% d‐ferrite is present after this steel is quenched from the solution annealing 

temperature of 

 1065

 

oC as Al

 is

 a strong

 ferrite

 former.

• It is easily worked in this condition but it rapidly “work hardens”* because of  its low Ni 

content.

• It is also hardened by ageing at 565 oC when an Al‐based compound is precipitated.

• An 

ageing 

treatment 

at 

510 o

C gives 

higher 

strength 

at 

the 

expense 

of  

lower 

ductility.

• - PH stands for “precipitation hardened”.

• Recall the concept of work hardening in bcc steels by dislocation pinning by carbon.

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600 Series

 Precipitation

 Hardening

 

Martensitic SS:•   Have corrosion resistance comporable to 300 series austentic grades but can be 

precipitation hardened

 for

 increased

 strength!

•   Key: High strength + corrosion resistance BOTH.

•   Why?  Aerospace industry  – defense budgets determined 2% of  GDP spent dealing with 

corrosion so developed high strength corrosion resistant steel to replace alloy steels.

•   Lockheed‐Martin Joint Striker Fighter  – 1st aircraft to use PH SS for entire airframe.

•   Common Grades:

•   630 grade = 17‐4 PH (17% Cr, 4% Ni), 

•   17‐4 PH, 

•   15‐

PH

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SSINA Stainless Steel Design Guidelines

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SSINA Stainless Steel Design Guidelines

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SSINA Stainless Steel Design Guidelines

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DUPLEX SS

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Characteristics of  Duplex stainless steels

•   Excellent resistance to stress corrosion cracking 

•  Very high mechanical strength 

•   Excellent resistance to pitting and crevice corrosion 

•  High resistance to general corrosion in a variety of  environments

•  Low thermal expansion 

•  High resistance to erosion corrosion and corrosion 

fatigue 

•  Good weldability

•  Lower 

life 

cycle 

cost

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Duplex microstructure

•  The austenite islands 

(light) are embedded in 

a continuous

 ferrite

 

(dark) matrix.

•  The duplex 

microstructure typically 

contains 45

‐65%

 

austenite and 35‐55% 

ferrite.

 Austenite Ferrite

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Yield Strength 0,2% Austenitic vs Duplex Stainless Steel

0

400

500

600

200

300

100

316L

SAF

2304

904L

SAF

2205

6Mo+N

SAF2507

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Solidif ication mechanism of aDuplex Stainless Steel

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Stress

 

strain

 

curves

Austenite,

 

ferrite

 

and

 

duplex

0,0 0,2 0,4 0,6 0,80

200

400

600

800

1000

austeniteduplex (2205)

ferrite

   S   t  r  e  s  s   [   M   P  a   ]

Strain

ferrite

duplex

austenite

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Conclusions

Key 

Areas

•  Good Weldability

•  Uses Conventional Welding Processes

•  Joint Design

•  Role of  Nitrogen

•  Heat Input Important

•   Interpass Temperature

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Welding

 

Stainless

•   There are 2 common grades of  stainless: 304L (welded using 308L filler), and 316L which is 

welded using

 316L

 filler.

•   Why is 308L filler used for 304L? Basically there are a number of  grades that do similar  jobs, 302L, 303L and 304L (they are 17/7, 18/8 and 19/9 respectively). 308L is 20/10 so can be used to weld 

all 3 grades.

•   Stainless is easy to weld but very difficult to keep flat, the coefficient of  linear expansion is 1.7 

times that of  mild steel. There isn’t much you can do about that except to weld it quickly and by 

doing so minimise the heat input.

•   304 and 316 (as opposed to the L low carbon versions) suffer from weld 

decay. When heated to 

welding temperatures the Chromium combines with the Carbon leaving the steel short of  Chromium and therefore unable to self  repair itself. 

•   This was virtually eliminated by introducing stabilised stainless steels 347 and 321 which contain 

Niobium 

or Titanium which sacrifices itself  to save the Chromium, however, when lower carbon 

versions 304L and 316L were introduced the problem of  weld decay was eliminated. These days 

the 

higher 

(in 

fact, 

normal) 

carbon 

versions 

are 

only 

used 

for 

applications 

where 

heat 

resistance 

is 

needed.

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Stainless

 

Steel

 

Filler

 

Metal

 

Choice* depends on environment ‐ if  Sulphurous it must be 410 

** preheat of  150°C required 

304L 316L 310 347 321 410 430  Mild 

Steel

308L 308L 310 308L 308L 309L 309L 309L   304L

308L 316L 310 316L 316L 309L 309L 309L   316L

310 310 310 310 310 309L 310 310   310

308L 316L 310 347 347 309L 309L 309L   347308L 326L 310 347 318 309L 309L 309L   321

309L 309L 309L 309L 309L 410/309L* 309L 309L   410

309L 309L 310 309L 309L 309L 309L** 309L   430

309L 309L 310 309L 309L 309L 309L  Mild 

Steel

Mild 

Steel