ASTM B473
Standard Specification for UNS N08020, UNS N08024, and UNS N08026
Nickel Alloy Bar and Wire
Alloy 20, also known as Carpenter 20, is a nickel-iron-chromium
austenitic alloy that was developed for maximum resistance to acid
attack, specifically sulfuric acid. This superalloy has excellent
resistance to general corrosion, pitting, and crevice corrosion in
chemicals containing chlorides and sulfuric, phosphoric, and nitric
acids. It also contains niobium for stabilization against
sensitization and resultant intergranular corrosion. Carpenter 20
combines excellent corrosion resistance with elevated mechanical
properties and relatively easy fabrication. Although originally
designed for use in sulfuric acid related industries, Alloy 20 is
now a popular choice for a wide variety of industries including the
chemical, food, pharmaceutical, and plastics industries. In
addition, this superalloy is used in heat exchangers, mixing tanks,
metal cleaning and pickling equipment, and piping.
There has long been a debate on whether Carpenter 20 is a stainless
steel or a nickel alloy because the nickel content is right on the
border of defining it as one way or the other. So, depending on who
you talk to this alloy may be referred to as alloy 20 Stainless
Steel or as a nickel alloy. Either way it is still great for
corrosion resistance.
Chemical Composition, %
| Ni | Fe | Cr | Cu | Mo | Nb | C | Mn | P | S | Si |
| 32.00-38.00 | Balance | 19.0-21.0 | 3.0-4.0 | 2.0-3.0 | 8xC-1.0 max | .07max | 2.0 max | .045 max | .035 max | 1.0 max |
ASTM Specifications
| Pipe Smls | Pipe Welded | Tube Smls | Tube Welded | Sheet/Plate | Bar | Forging | Fitting |
| B729 | B464 | B729 | B468 | B463 | B473 | B462 | B366 |
| Form | Tensile Min. | Yield Min. (.2% offset) | Elongation Min. | Reduction of Area Min. |
| Bar (hot or cold finished) | 80 ksi | 35 ksi | 30% | 50% |
| Sheet/Plate | 80 ksi | 35 ksi | 30% | - |
Benefits of Alloy 20 UNS N08020 Round Bar
The benefits of a Alloy 20 Round Bars -
Excellent resistance to corrosion, crevice corrosion, and pitting
Perfect for use around sulfuric, phosphoric, and nitric acids
Ease of fabrication and elevated mechanical properties
Applications of Alloy 20 UNS N08020 Round Bar
The applications of the Alloy 20 Round Bars are -Synthetic rubber
manufacturing equipment; Processing of pharmaceuticals, plastics
and organic and heavy chemicals; Tanks, piping, heat exchangers,
pumps, valves, and other process equipment; Acid cleaning and
pickling equipment; Chemical process piping, reactor vessels;
Bubble caps.
In what forms is Alloy 20 Available at HT PIPE?
Sheet
Plate
Bar
Pipe & Tube (welded & seamless)
Fittings
oflanges, slip-ons, blinds, weld-necks, lapjoints, long welding
necks, socket welds, elbows, tees, stub-ends, returns, caps,
crosses, reducers, and pipe nipples
Welding Wire (AWS Classifications: ER320LR and E320LR-16)
What are the characteristics of Alloy 20?
Excellent general corrosion resistance to sulfuric acid
Excellent resistance to chloride stress corrosion cracking
Excellent mechanical properties and fabricability
Minimal carbide precipitation during welding
Excels in resisting corrosion to hot sulfuric acids
Differences between hot rolled steel and cold rolled steel
Hot Rolled Steel
Hot rolling is a mill process which involves rolling the steel at a
high temperature (typically at a temperature over 1700° F), which
is above the steel’s recrystallization temperature. When steel is
above the recrystallization temperature, it can be shaped and
formed easily, and the steel can be made in much larger sizes. Hot
rolled steel is typically cheaper than cold rolled steel due to the
fact that it is often manufactured without any delays in the
process, and therefore the reheating of the steel is not required
(as it is with cold rolled). When the steel cools off it will
shrink slightly thus giving less control on the size and shape of
the finished product when compared to cold rolled.
Uses: Hot rolled products like hot rolled steel bars are used in
the welding and construction trades to make railroad tracks and
I-beams, for example. Hot rolled steel is used in situations where
precise shapes and tolerances are not required.
Cold Rolled Steel
Cold rolled steel is essentially hot rolled steel that has had
further processing. The steel is processed further in cold
reduction mills, where the material is cooled (at room temperature)
followed by annealing and/or tempers rolling. This process will
produce steel with closer dimensional tolerances and a wider range
of surface finishes. The term Cold Rolled is mistakenly used on all
products, when actually the product name refers to the rolling of
flat rolled sheet and coil products.
When referring to bar products, the term used is “cold finishing”,
which usually consists of cold drawing and/or turning, grinding and
polishing. This process results in higher yield points and has four
main advantages:
Cold drawing increases the yield and tensile strengths, often
eliminating further costly thermal treatments.
Turning gets rid of surface imperfections.
Grinding narrows the original size tolerance range.
Polishing improves surface finish.
All cold products provide a superior surface finish, and are
superior in tolerance, concentricity, and straightness when
compared to hot rolled.
Cold finished bars are typically harder to work with than hot
rolled due to the increased carbon content. However, this cannot be
said about cold rolled sheet and hot rolled sheet. With these two
products, the cold rolled product has low carbon content and it is
typically annealed, making it softer than hot rolled sheet.
Uses: Any project where tolerances, surface condition,
concentricity, and straightness are the major factors.
