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CHAPTER 12

Materials of Construction

Material properties are of great importance in all aspects of rotating

equipment design and manufacture. It is essential to check the up-to-date

version of the relevant British Standards or equivalent when choosing or

assessing a material. The most common materials used for rotating

equipment are divided into the generic categories of carbon, alloy, stainless

steel, and non-ferrous.

12.1 Plain carbon steels basic dataTypical properties are shown in Table 12.1.

Table 12.1 Plain carbon steel: properties

Type %C %Mn Yield, R e UTS, Rm(MN/m2) (MN/m2)

Low C steel 0.1 0.35 220 320

General structural steel 0.2 1.4 350 515

Steel castings 0.3 270 490

12.2 Alloy steels basic dataAlloy steels have various amounts of Ni, Cr, Mn, or Mo added to improve

properties. Typical properties are shown in Table 12.2.

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Engineers Guide to Rotating Equipment296

Table 12.2 Alloy steels: properties

Type %C Others (%) R e(MN/m2) Rm(MN/m

2)

Ni/Mn steel 0.4 0.85 Mn 480 680

1.00 Ni

Ni/Cr steel 0.3 0.5 Mn 800 910

2.8 Ni

1.0 Cr

Ni/Cr/Mo steel 0.4 0.5 Mn 950 1050

1.5 Ni

1.1 Cr

0.3 Mo

12.3 Stainless steels basic dataStainless steel is a generic term used to describe a family of steel alloys

containing more than about 11 per cent chromium. The family consists of

four main classes, subdivided into about 100 grades and variants. The main

classes are austenitic and duplex. The other two classes, ferritic and

martensitic, tend to have more specialized application and so are not so

commonly found in general rotating equipment use. The basic

characteristics of each class are given below.

Austenitic The most commonly used basic grades of stainless steel are

usually austenitic. They have 1725 per cent Cr, combined with 820 per

cent Ni, Mn, and other trace alloying elements which encourage the

formation of austenite. They have low carbon content, which makes them

weldable. They have the highest general corrosion resistance of the family

of stainless steels.

Ferritic Ferritic stainless steels have high chromium content (>17 per cent

Cr) coupled with medium carbon, which gives them good corrosion

resistance properties rather than high strength. They normally have some

Mo and Si, which encourage the ferrite to form. They are generally non-

hardenable. Martensitic This is a high-carbon (up to 2 per cent C), low-chromium (12

per cent Cr) variant. The high carbon content can make it difficult to weld.

Duplex Duplex stainless steels have a structure containing both austenitic

and ferritic phases. They can have a tensile strength of up to twice that of

straight austenitic stainless steels and are alloyed with various trace

elements to aid corrosion resistance. In general, they are as weldable as

austenitic grades but have a maximum temperature limit, because of the

characteristic of their microstructure.

Table 12.3 gives basic stainless steel data.

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MaterialsofConstruction

297

AISI Other

classifications

Type + Yield

Fty

(ksi)

[(Re)

MPa]

Ultimate

Ftu

(ksi)

[(Rm)

MPa]

E(%)

50

mm

HRB %C %Cr %

others *

Properties

302 ASTM A296

(cast),

Wk 1.4300,

18/8, SIS 2331

Austenitic 40 [275.8] 90 [620.6] 55 85 0.15 1719 810 Ni A general

purpose

stainless steel.

304 ASTM A296,

Wk 1.4301,

18/8/LC,

SIS 2333,

304S18

Austenitic 42 [289.6] 84 [579.2] 55 80 0.08 1820 812 Ni An economy

grade.

304L ASTM A351,

Wk 1.4306,

18/8/ELC,

SIS 2352,

304S14

Austenitic 39 [268.9] 80 [551.6] 55 79 0.03 1820 812 Ni Low C to avoid

intercrystalline

corrosion after

welding.

316 ASTM A296,

Wk 1.4436,

18/8/Mo,SIS 2243,

316S18

Austenitic 42 [289.6] 84 [579.2] 50 79 0.08 1618 1014

Ni

Addition of Mo

increases

corrosionresistance.

316L ASTM A351,

Wk 1.4435,

18/8/Mo/ELC,

316S14,

SIS 2353

Austenitic 42 [289.6] 81 [558.5] 50 79 0.03 1618 1014

Ni

Low C weldable

variant of 316.

Table 12.3 Stainless steels basic data

Stainless steels are commonly referred to by their AISI equivalent classification (where appropriate).

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EngineersGuidetoRotatingEquipment

298321 ASTM A240,

Wk 1.4541,

18/8/Ti,

SIS 2337,

321S18

Austenitic 35 [241.3] 90 [620.6] 45 80 0.08 1719 912

Ni

Variation of 304

with Ti added to

improve

temperature

resistance.

405 ASTM

A240/A276/

A351,

UNS 40500

Ferritic 40 [275.8] 70 [482.7] 30 81 0.08 11.514.5 1 Mn A general purpose

ferritic stainless

steel.

430 ASTM

A176/A240/

A276,

UNS 43000,

Wk 1.4016

Ferritic 50 [344.7] 75 [517.1] 30 83 0.12 1418 1 Mn Non-hardening

grade with good

acid-resistance.

403 UNS S40300,

ASTM

A176/A276

Martensitic 40 [275.8] 75 [517.1] 35 82 0.15 11.513 0.5 Si Turbine grade of

stainless steel.

410 UNS S40300,

ASTM

A176/A240,

Wk 1.4006

Martensitic 40 [275.8] 75 [517.1] 35 82 0.15 11.513.5 4.56.5

Ni

Used for machine

parts, pump shafts,

etc.

255 (Ferralium) Duplex 94 [648.1] 115 [793] 25 280

HV

0.04 2427 4.56.5

Ni

Better resistance to

SCC than 316.

High strength. Max.

temp 575 F

(301 C) due to

embrittlement.

Avesta SAF

2507 ,

UNS S32750

'Super'

duplex

40% ferrite

99 [682.6] 116 [799.8] ~ 25 300

HV

0.02 25 7 Ni,

4 Mo,

0.3 N

* Main constituents only shown.+All austenitic grades are non-magnetic; ferritic and martensitic grades are magnetic.

Avesta trade mark.

Table 12.3 Cont.

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Materials of Construction 299

12.4 Non-ferrous alloys basic dataThe term non-ferrous alloys is used for those alloy materials that do not

have iron as their base element. The main ones used for mechanicalengineering applications, with their ultimate tensile strength ranges, are:

nickel alloys 4001200 MN/m2

zinc alloys 200360 MN/m2

copper alloys 2001100 MN/m2

aluminium alloys 100500 MN/m2

magnesium alloys 150340 MN/m2

titanium alloys 4001500 MN/m2

The main ones in use are nickel alloys, in which nickel is frequently alloyed

with copper or chromium and iron to produce material with high

temperature and corrosion resistance. Typical types and properties are

shown in Table 12.4.

Table 12.4 Nickel alloys: properties

Alloy type Designation Constituents (%) UTS (MN/m2)

NiCu UNS N04400 66 Ni, 31 Cu, 1 Fe, 415

(Monel) 1 Mn

NiFe Ni lo 36 36 Ni, 64 Fe 490

NiCr Inconel 600 76 Ni, 15 Cr, 8 Fe 600

NiCr Inconel 625 61 Ni, 21 Cr, 2 Fe, 800

9 Mo, 3 Nb

NiCr Hastelloy C276 57 Ni, 15 Cr, 6 Fe, 7501 Co, 16 Mo, 4 W

NiCr Nimonic 80A 76 Ni, 20 Cr 8001200

(age hardenable)

NiCr Inco Waspalloy 58 Ni, 19 Cr, 13 Co, 8001000

(age hardenable) 4 Mo, 3 Ti, 1 Al

12.5 Material traceabilityThe issue of material traceability is an important aspect of the manufacture

of high-integrity rotating equipment. Most technical codes and standards

make provision for quality assurance activities designed to ensure that

materials of construction used in the pressure envelope are traceable.

Figure 12.1 shows the chain of traceability which operates for rotating

equipment materials. Note that although all the activities shown are

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Engineers Guide to Rotating Equipment300

Fig. 12.1 The chain of traceability for materials

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Materials of Construction 301

available for use (i.e. to be specified and then implemented) this does not

represent a unique system of traceability suitable for all materials. In

practice there are several levels in use, depending on both the type ofmaterial and the nature of its final application. The most common document

referenced in the material sections of rotating equipment specifications is

the European Standard EN 10 204: (1991) Metallic products types of

inspection documents. It provides for two main levels of certification:

Class 3 and Class 2 (see Table 12.5).

Table 12.5 Material traceability: EN 10 204 classes

EN 10 204 Document Compliance with: Test Test basiscertificate validation results

type by the order technical included Specific Non-specific

rules *

3.1A I Yes

3.1B M(Q) Yes

3.1C P Yes

3.2 P + M(Q) Yes

2.3 M Yes

2.2 M Yes

2.1 M No

I An independent (third party) inspection organization.

P The purchaser.

M(Q) An independent (normally QA) part of the material manufacturer's organization.

M An involved part of the material manufacturers organization.

* Normally the technical rules on material properties given in the relevant material standard (and

any applicable technical code).

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