3. classes of alloys in refinery use

8/10/2019 3. Classes of Alloys in Refinery Use

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EDS 2004/Metallurgy 2-1

Classes of Alloys in Refinery Use


Outcomes

Recall alloy types which are commonly used

in refineries

Recall specific examples of each alloy type

Recall factors (advantages/disadvantages)

which govern the use of the alloy


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Classes of Refinery Metallurgy

Carbon and killed carbon steels

Low alloy (Cr-Mo) Steels

Stainless steels

Nickel alloys

Copper alloys

Titanium alloys

Aluminum alloys


Carbon Steels

Alloy of Fe and C

Carbon content affects mechanical properties

High C

High strength

Low ductility Processing conditions also affect mechanical

properties

Too many details for this course

Harden when quenched from above 1333oF


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Refinery Metallurgy

Carbon steel is the default material of

construction used in refineries

Inexpensive

Easy to work with

Normally economically satisfactory

Cost vs. life expectancy

Other materials used only when carbon steel

is unsatisfactory


Carbon Steels

Carbon steel processed in two forms

Ordinary Carbon steel

Proper designation would be rimmed or

semi killed carbon steel

Killed carbon steel

Killing is a refining process

Affects

Mechanical properties

Cleanliness of steel


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Carbon Steels

Killed Steel used

H2S, HF, CN- service

Lack of inclusion helps prevent blisters

High temperature hydrogen service

Lack of inclusion helps prevent blisters

Low temperature service

Minimum temperatures as low as -50oF (-45oC)

Ordinary carbon steel

Use in all other services


Low Alloy (Cr-Mo) Steels

1 Cr- Mo; 1 Cr- Mo

2 Cr- Mo

5 Cr- Mo

9 Cr- Mo


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1 Cr- Mo; 1 Cr- Mo

Used where improved properties over carbon steel

are required

Design temperature 1200oF vs. 1000oF

High temperature strength

Resistance to high temp hydrogen attack

High temperature sulfur

Contradictory data exist

Similar properties to carbon steel

Resistance to high temperature H2S/H2


1 Cr- Mo; 1 Cr- Mo

Primary uses

Reactor shells for high temperature processes

Heater tubes

Piping

Exchangers


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1 Cr- Mo; 1 Cr- Mo

Primary cautions

High hardenability weld cracking

Creep embrittlement

Discussed later


2 Cr-1 Mo

Used where improved properties over 1 Cr- Mo

are required


Resistance to high temp hydrogen attack

High temperature sulfur Contradictory data exist

Similar properties to 1 Cr- Mo

Design temperature



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2 Cr-1 Mo

Primary uses

Reactor shells for high temperature processes

Heater tubes

Piping

Exchangers


2 Cr-1 Mo

Primary cautions


Temper embrittlement

Discussed later


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5 Cr- Mo

Used where improved properties over 2 Cr-1 Mo

are required


Resistance to high temperature hydrogen attack


Similar properties to 2 Cr-1 Mo

Design temperature



5 Cr- Mo

Primary uses

Piping

Exchangers

Primary cautions



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9 Cr-1 Mo

Used where improved properties over 5 Cr- Mo

are required





Similar properties to 5 Cr- Mo

Design temperature


9 Cr-1 Mo

Primary uses

Heater tubes

Primary cautions



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Stainless Steels

Ferritic

Austenitic

Martensitic


Stainless Steels, Ferritic

405 11 13% Cr, aluminum

410S 11 13% Cr, low carbon

Body center cubic (ferrite)

Just enough Cr to be stainless


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Used where improved properties over 9 Cr-1

Mo are required



Generally not used for

Pressure boundaries

Where welding is required

Naphthenic acids service



Primary uses

Cladding over carbon or low Cr steels

Trays

Exchanger tubes

Primary cautions 885 embrittlement (discussed later)

Potentially low toughness

Weld HAZ


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Stainless Steels, Austenitic

Face center cubic (austenite)

304 18% Cr, 8% Ni

316 Approximately 304 + 2% Mo

317 Approximately 304 + 3% Mo

321 Approximately 304 + Ti

347 Approximately 304 + Nb

High Ni, Mo Stainless



Theoretically available grades

Normal and L grades often

double stamped

H grades difficult to find,

316H nearly unavailable

No L grade for 321 and 347

(chemically stabilized rather

than low C 347H347

321H321

317H317317L

316H316316L

304H304304L


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Used where improved properties over low alloy

steels are required





Design temperature (for high carbon material)



Carbon is important

Normal and low C material good to 1000oF

H grade materials good to 1500oF

L grades dont sensitize during welding

Discussed later


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Molybdenum is important (316, 317)

Resists pitting from Cl-

May or may not resist cracking from Cl-

Resists naphthenic acid corrosion

Normally need 2.5% Moly

316 may be ok

Normally want 317



Titanium and niobium (columbium) are

important (321, 347)

Chemically stabilize steels

Dont sensitize during welding


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Primary uses

Heater tubes (347H)

Oxidation, sensitization resistance

Exchanger tubes (304)

Linings (304)

Aqueous H2S service

High temperature components (304)

Strength and code allowable temperatures

High pressure hydrotreating piping (321, 347)



High Ni, Mo stainless

Alloy 20, 254SMO, Al-6XN

Used in reducing acids such as H2SO4

Sulfuric acid alkylation units

Used when resistance to corrosionintermediate between 300 series stainless

and Hastelloy C-276 are required


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Primary cautions

Subject to sensitization

May lead to corrosion

Subject to pitting and stress corrosion

cracking from Cl-

Use care in cooling water applications

Liquid metal embrittlement by zinc

Be careful of galvanized materials

All issues discussed later


Stainless Steels, Martensitic

410 12% Cr (higher C than 410S)

Not used as pressure boundary

Used for

Aqueous corrosion resistance

Strength Wear resistance

Used in

Shafts, pumps, turbine blades


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Nickel Alloys

Ni, Cr, Fe alloys Alloy 800 (series)

Ni, Cr, Mo alloys (C-276, alloy 625)

Monel


Ni, Cr, Fe Alloys

Face center cubic (austenite)

800, 800H, 800HT

Carbon, aluminum and titanium vary

825

Trade name of these alloys is Incoloy


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Ni, Cr, Fe Alloys

Use 800 series where improved properties

over austenitic stainless steel is required


High temperature oxidation

Creep


High temperature H2S/H2

Design temperature


Ni, Cr, Fe Alloys

Use 825 where improved properties over

austenitic stainless steels is required

Cl- SCC

Reducing acids

Ammonium bisulfide


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Ni, Cr, Fe Alloys

Primary uses 800, 800H,800HT

Heater tubes

Pig tails for H2 reformers

Primary uses 825

Hydrotreater reactor effluent air coolers

Low point drains


Ni, Cr, Fe Alloys

Primary cautions

Some alloys subject to sensitization

Follow suppliers temperature

recommendations

Some alloys embrittle when operatedbetween 550750oC (10201380oF)


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Ni, Cr, Mo Alloys

Alloy C-276

Trade name Hastelloy

Alloy 625

Trade name Inconel

Alloys C2000 and 59

Newer alloys which may be used in the future


Ni, Cr, Mo Alloys

Use when high resistance to aqueous corrosion

is required

Acid chlorides (ammonium chloride)

Immune to Cl- stress corrosion cracking

Reducing acids (sulfuric and hydrochloric) Oxidizing acids (nitric acid)

Lower resistance than with reducing acids

Ammonium bisulfide


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Monel

Alloy 400

Monel or Monel 400 are trade names

70 Ni, 30 Cu

Resists

HCl

HF

Caustic cracking


Monel

Primary uses

HF Alkylation units

All areas where the corrosion rate exceeds

acceptable limits for carbon steel

Mostly high temperature areas

Crude unit overheads

Linings, rings trays

Hot and or concentrated caustic applications


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Monel

Primary cautions

Not resistant to oxidizing environments

Applications over 300oF (150oC) may not be

successful

Highly resistant to but not completely immune

from ammonia SCC


Copper Alloys

Cupronickels

70 Cu, 30 Ni

90 Cu, 10 Ni

Inhibited admiralty brass

71 Cu, 28 Zn, 1 Sn, 0.04 As

Aluminum brass, arsenical

77.5 Cu, 20.5 Zn, 2 Al, 0.1 As

Naval Brass

60 Cu, 39.25 Zn, 0.75 Sn


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Copper Alloys

Primary uses

Heat exchangers

Use dictated by water side

Use for seawater

Use for untreated fresh water


Copper Alloys

Primary cautions

Ammonia stress corrosion cracking

Cu Ni less sensitive than brasses

Sulfur compounds

May cause excessive corrosion

Water velocity

High velocities, higher corrosion (varies

by alloy)

High concentrations of oxygen/oxidizers

May increase corrosion rates


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Titanium

Several grades available

Highly reactive material

Oxide film makes highly corrosion resistant

Highly resistant to Cl-


Titanium

Primary uses

Exchangers

May be dictated by water or process

Primary caution

Subject to hydriding when coupled to steel attemperatures above 80oC (176oF)

Hydriding makes titanium brittle


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Aluminum Alloys

Many classes of alloys

Many alloys within each class

Mechanical and corrosion properties vary

Primary refinery uses

Fin Fans

Cold boxes

Rotating equipment

Not piping or vessels

3. classes of alloys in refinery use

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