new - 02 classes of alloys in refinery use

RE Alloys/2-1

Classes of Alloys in Refinery Use

RE Alloys/2-2

Outcomes

Recall alloy types which are commonly used in refineriesRecall specific examples of each alloy typeRecall factors (advantages/disadvantages) which govern the use of the alloy

RE Alloys/2-3

Classes of Refinery Metallurgy

Carbon and killed carbon steelsLow alloy (Cr-Mo) SteelsStainless steelsNickel alloysCopper alloysTitanium alloysAluminum alloys

RE Alloys/2-4

Carbon Steels

Alloy of Fe and C– Carbon content affects mechanical properties

— High CHigh strengthLow ductility

– Processing conditions also affect mechanical properties— Too many details for this course

– Harden when quenched from above 1333oF

RE Alloys/2-5

Refinery Metallurgy

Carbon steel is the default material of construction used in refineries– Inexpensive– Easy to work with– Normally economically satisfactory

— Cost vs. life expectancyOther materials used only when carbon steel is unsatisfactory

RE Alloys/2-6

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

RE Alloys/2-7

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

RE Alloys/2-8

Low Alloy (Cr-Mo) Steels

1 Cr-½Mo; 1¼ Cr-½Mo2¼ Cr-½Mo5 Cr-½Mo9 Cr-½Mo

RE Alloys/2-9

1 Cr-½Mo; 1¼ Cr-½Mo

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 existSimilar properties to carbon steel – Resistance to high temperature H2S/H2

RE Alloys/2-10

1 Cr-½Mo; 1¼ Cr-½Mo

Primary uses– Reactor shells for high temperature processes– Heater tubes– Piping– Exchangers

RE Alloys/2-11

1 Cr-½Mo; 1¼ Cr-½Mo

Primary cautions– High hardenability – weld cracking– Creep embrittlement

— Discussed later

RE Alloys/2-12

2¼ Cr-1 Mo

Used where improved properties over 1¼ Cr-½Mo are required– High temperature strength– Resistance to high temp hydrogen attack– High temperature sulfur

— Contradictory data existSimilar properties to 1¼ Cr-½Mo – Design temperature– Resistance to high temperature H2S/H2

RE Alloys/2-13

2¼ Cr-1 Mo

Primary uses– Reactor shells for high temperature processes– Heater tubes– Piping– Exchangers

RE Alloys/2-14

2¼ Cr-1 Mo

Primary cautions– High hardenability – weld cracking– Temper embrittlement

— Discussed later

RE Alloys/2-15

5 Cr-½Mo

Used where improved properties over 2¼ Cr-1 Mo are required– High temperature strength– Resistance to high temperature hydrogen attack– High temperature sulfur

Similar properties to 2¼ Cr-1 Mo – Design temperature– Resistance to high temperature H2S/H2

RE Alloys/2-16

5 Cr-½Mo

Primary uses– Piping– Exchangers

Primary cautions– High hardenability – weld cracking

RE Alloys/2-17

9 Cr-1 Mo

Used where improved properties over 5 Cr-½Mo are required– High temperature strength– Resistance to high temperature hydrogen attack– High temperature sulfur– Resistance to high temperature H2S/H2

Similar properties to 5 Cr-½Mo – Design temperature

RE Alloys/2-18

9 Cr-1 Mo

Primary uses– Heater tubes

Primary cautions– High hardenability – weld cracking

RE Alloys/2-19

Stainless Steels

FerriticAusteniticMartensitic

RE Alloys/2-20

Stainless Steels, Ferritic

405 11 – 13% Cr, aluminum410S 11 – 13% Cr, low carbon– Body center cubic (“ferrite”)– Just enough Cr to be stainless

RE Alloys/2-21

Stainless Steels, Ferritic

Used where improved properties over 9 Cr-1Mo are required– High temperature sulfur– Resistance to high temperature H2S/H2

Generally not used for– Pressure boundaries– Where welding is required– Naphthenic acids service

RE Alloys/2-22

Stainless Steels, Ferritic

Primary uses– Cladding over carbon or low Cr steels– Trays– Exchanger tubes

Primary cautions– 885 embrittlement (discussed later)– Potentially low toughness

— Weld HAZ

RE Alloys/2-23

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

RE Alloys/2-24

Stainless Steels, Austenitic

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

RE Alloys/2-25

Stainless Steels, Austenitic

Used where improved properties over low alloy steels are required– High temperature strength– Resistance to high temperature hydrogen

attack– High temperature sulfur– Resistance to high temperature H2S/H2

– Design temperature (for high carbon material)

RE Alloys/2-26

Stainless Steels, Austenitic

Carbon is important– Normal and low C material good to 1000oF– H grade materials good to 1500oF– L grades don’t sensitize during welding

— Discussed later

RE Alloys/2-27

Stainless Steels, Austenitic

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 okNormally want 317

RE Alloys/2-28

Stainless Steels, Austenitic

Titanium and niobium (columbium) are important (321, 347)– Chemically stabilize steels

— Don’t sensitize during welding

RE Alloys/2-29

Stainless Steels, Austenitic

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)

RE Alloys/2-30

Stainless Steels, Austenitic

High Ni, Mo stainless– Alloy 20, 254SMO, Al-6XN– Used in reducing acids such as H2SO4

— Sulfuric acid alkylation units– Used when resistance to corrosion

intermediate between 300 series stainless and Hastelloy C-276 are required

RE Alloys/2-31

Stainless Steels, Austenitic

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

RE Alloys/2-32

Stainless Steels, Martensitic

410 12% Cr (higher C than 410S)Not used as pressure boundaryUsed for– Aqueous corrosion resistance– Strength– Wear resistance

Used in– Shafts, pumps, turbine blades

RE Alloys/2-33

Nickel Alloys

Ni, Cr, Fe alloys Alloy 800 (series)Ni, Cr, Mo alloys (C-276, alloy 625)Monel

RE Alloys/2-34

Ni, Cr, Fe Alloys

Face center cubic (austenite) – 800, 800H, 800HT

— Carbon, aluminum and titanium vary– 825– Trade name of these alloys is Incoloy

RE Alloys/2-35

Ni, Cr, Fe Alloys

Use 800 series where improved properties over austenitic stainless steel is required– High temperature strength– High temperature oxidation– Creep– High temperature sulfur– High temperature H2S/H2

– Design temperature

RE Alloys/2-36

Ni, Cr, Fe Alloys

Use 825 where improved properties over austenitic stainless steels is required– Cl- SCC– Reducing acids– Ammonium bisulfide

RE Alloys/2-37

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

RE Alloys/2-38

Ni, Cr, Fe Alloys

Primary cautions– Some alloys subject to sensitization– Follow suppliers temperature

recommendations— Some alloys embrittle when operated

between 550–750oC (1020–1380oF)

RE Alloys/2-39

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

RE Alloys/2-40

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

RE Alloys/2-41

Monel

Alloy 400– Monel or Monel 400 are trade names– 70 Ni, 30 Cu

Resists– HCl– HF– Caustic cracking

RE Alloys/2-42

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

RE Alloys/2-43

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

RE Alloys/2-44

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

RE Alloys/2-45

Copper Alloys

Primary uses– Heat exchangers

— Use dictated by water side— Use for seawater— Use for untreated fresh water

RE Alloys/2-46

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

RE Alloys/2-47

Titanium

Several grades availableHighly reactive material– Oxide film makes highly corrosion resistant– Highly resistant to Cl-

RE Alloys/2-48

Titanium

Primary uses– Exchangers

— May be dictated by water or processPrimary caution– Subject to hydriding when coupled to steel at

temperatures above 80oC (176oF)— Hydriding makes titanium brittle

RE Alloys/2-49

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