CIVE 2700 Lecture Notes - Weldability, Stainless Steel, Csa Group
28 Sep 2014
School
Department
Course
Professor
16/09/2014
1
Last class:
•Alloying
•Material composition
•Phase diagrams
•Steel production
Steels Cast Irons
Today:
1. Steel grades
2. Stainless steel
Mill Symbol
Bar Size (diameter)
Blank Space
Grade Symbol- one line
(400) or two lines (500)
through five spaces
Weldable
Structural Steel
Structural steel is used for different types of structural members
Columns & beams Bracings
www.gic-edu.com www.castconnex.com
Structural Steel Grades
1. Type W -Weldable Steel
2. Type WT -Weldable Notch Tough Steel
3. Type R -Atmospheric Corrosion-Resistant Steel
4. Type A - Atmospheric Corrosion-Resistant Weldable Steel
5. Type AT - Atmospheric Corrosion-Resistant Weldable Notch Tough Steel
6. Type Q - Quenched and Tempered Low Alloy Steel Plate
7. Type QT - Quenched and Tempered Low Alloy Notch-Tough Steel Plate
The seven types of structural steel available in Canada, as specified in
CSA G40.20-04: General Requirements for Structural Quality Steel,
(Issued by Canadian Standards Association) are as follows:
Every country has specification or standards for identifying steel types.
Designation differs from standard to standard. USA-ASTM, Canada-CSA
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Atmospheric corrosion-resistant steel
Ordinary carbon steel
Type W versus Type R
www.corrosionlab.com
Structural Steel-CSA Designation
These seven types and eight strength levels have been combined
into twenty-five grades, as follows:
400WT
Grade is identified by a number and one or two letters:
e.g. 400 WT means Fy= 400 MPa; Weldable Notch Tough Steel
Composition and Use
1. Type W - Weldable Steel
Typical Chemical Composition: (differs for different yield strengths*)
0.20-0.26% C, 0.50-1.50% Mn, 0.04% P, 0.05% S, 0.40% Si and 0.10% other (Cd,
V, Al)
Use:
•Suitable for field or shop welding where notch toughness at low
temperature is not a design requirement. (Not recommended for low
temperature applications)
•Applications may include buildings and bridge members (beams &
columns) in compression
e.g. Grade 300W is recommended for normal building construction where
field or shop welding procedures are used-design does not consider impact)
*For more details on composition see Table 6-4 in the Canadian
Institute of Steel Construction (CISC) Handbook of Steel Construction
or the CSA standard G40.20/21
2. Type WT - Weldable Notch Tough Steel
Typical Chemical Composition:
0.20-0.26% C, 0.08-1.50% Mn, 0.03% P, 0.04% S, 0.15-0.40% Si and 0.10%
other
Use:
•Suitable for welded construction where notch toughness at low
temperature is a design requirement-designer should specify Charpy
V-Notch test temperature and energy level.
•Applications may include primary tension members in bridges.
e.g. 300WT is easily weldable with good impact properties, suitable
for low temperature applications, due to its chemical composition.
Notch toughness: passes minimum CharpyV-notch impact test
requirement
3. Type R – Atmospheric Corrosion-Resistant Steel
Typical Chemical Composition:
0.16% C, 0.75% Mn, 0.05-0.15% P, 0.04% S, 0.75% Si, 0.30-1.25% Cr, 0.90% Ni,
0.20-0.60% Cu
Use:
•Display an atmospheric corrosion resistance four times that of plain
carbon steels.Weldable up to a maximum thickness of 14 mm -
often used in bare (unpainted) condition-staining problem!
•Applications include unpainted roofing, siding, light structural members,
art works etc., where notch toughness at low temperature is not a
design requirement
Building siding Roof
www.raic.org www.mgerwing.wordpress.com
4. Type A – Atmospheric Corrosion-Resistant Weldable Steel
Typical Chemical Composition:
0.20% C, 0.75-1.60% Mn, 0.025-0.03% P, 0.035-0.04% S, 0.15-0.50% Si, 0.70% Cr,
0.25-0.90% Ni, 0.20-0.60% Cu
Use:
•Display an atmospheric corrosion resistance four times that of plain carbon
steels – suitable for welded construction in all thicknesses where notch
toughness at low temperature is not a design requirement – Widely used
in painted or unpainted condition – staining problem!
•Applications are more common in bridges in compression applications
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“Weathering” Steel
Weathered steel
sculpture
Note staining
on concrete
base
Runoff of water from upper portions of a structure tend to produce long-lasting
streaks of red oxide on its lower portions. Special attention must be paid to the
drainage of storm water to prevent staining of surrounding structures and
sidewalks.
Atmospheric Corrosion Resistant Steels are referred to as “weathering” steel
www.events.nace.org
•Was developed to reduce maintenance, e.g. no painting (save money).
•After about 2 years, the surface oxidizes by developing a dense oxide skin
that seals out the atmosphere and retards further corrosion. The colour
changes from brown to much darker and reddish brown.
•This is in contrast to other steels that form a coarse, porous and flaky oxide
skin that allows the atmosphere to continue penetrating the steel.
Weathering steel pedestrian bridge New River Gorge Bridge
“Weathering” Steel
www.americanbridge.net
5. Type AT – Atmospheric Corrosion-Resistant Weldable
Notch Tough Steel
Typical Chemical Composition:
Similar to Type A
Use:
•Display an atmospheric corrosion resistance four times that of plain
carbon steels – suitable for welded construction where notch
toughness at low temperature is a design requirement – often used
in unpainted condition - designer should specify Charpy V-Notch
test temperature and energy level
•Applications include primary tension members in bridges
AT is used to get better behaviour at low temperatures,
which is generally not necessary for a building application
6. Type Q – Quenched and Tempered Low Alloy Steel Plate
Typical Chemical Composition:
0.20% C, 1.50% Mn, 0.03% P, 0.04% S, 0.15-0.40% Si, 0.0005-0.005% B
Use:
•Steel of this type is readily welded – welding and fabrication techniques
must not adversely affect properties of the plate, especially in the heat
affected zone.
•Applications may include bridges and similar structures
Type Q steels display a very high yield strength
and good resistance to brittle fracture.
Welding:
•Excessive temperature will compromise any tempering.
•Appropriate filler metal. Properties of base metal and filler need to be
matched as close as possible.
•Follow the welding process specifications (obtained from material supplier)
7. Type QT - Quenched and Tempered Low Alloy Notch-Tough
Steel Plate
Typical Chemical Composition:
Similar to Type Q
Use:
•Suitable for structures where notch toughness at low temperature is a
design requirement - designer should specify Charpy V-Notch test
temperature and energy level - readily welded - welding and fabrication
techniques must not adversely affect properties of the plate, especially
in the heat affected zone.
•Applications may include primary tension members in bridges and
similar elements
Structural Steel-ASTM Designation
•ASTM has its own alloy identification
•Begins with a letter ‘A’ followed by 2 to 4 numbers
•Commonly used structural steel:
•Carbon steels
•High strength low alloy steels (HSLA)
•Corrosion resistant high strength low alloy steels
•Quenched and tempered low alloy steels
•Valid for different shapes; plates, pipes and hollow sections
•For more in depth information refer to each ASTM specification:
(e.g. ASTM A36- Standard Specification for Carbon Structural Steel)
•For CSA refer to G40.20 and G40.21
Document Summary
Last class: alloying, material composition, phase diagrams, steel production. Structural steel is used for different types of structural members www. gic-edu. com www. castconnex. com. The seven types of structural steel available in canada, as specified in. Every country has specification or standards for identifying steel types. These seven types and eight strength levels have been combined into twenty-five grades, as follows: Grade is identified by a number and one or two letters: e. g. 400 wt means fy = 400 mpa; weldable notch tough steel. Composition and use: type w - weldable steel. Typical chemical composition: (differs for different yield strengths*) 0. 20-0. 26% c, 0. 50-1. 50% mn, 0. 04% p, 0. 05% s, 0. 40% si and 0. 10% other (cd, *for more details on composition see table 6-4 in the canadian. Institute of steel construction (cisc) handbook of steel construction or the csa standard g40. 20/21: type wt - weldable notch tough steel. 0. 20-0. 26% c, 0. 08-1. 50% mn, 0. 03% p, 0. 04% s, 0. 15-0. 40% si and 0. 10% other.
