Introduction
In the industrial materials landscape, the UNS N06625 nickel alloy
round bar stands as a paragon of high - performance materials. Its
wide - ranging applications across aerospace, marine, chemical, and
other industries are a testament to its remarkable properties. From
enduring the extreme conditions in aircraft engines to maintaining
structural integrity in corrosive chemical processing plants, this
alloy has proven to be indispensable. This article delves deep into
the chemical composition, mechanical properties, equivalent grades,
product standards, advantages, and applications of the UNS N06625
nickel alloy round bar, both in black bar and bright bar forms,
aiming to provide a comprehensive understanding of this remarkable
material.
Chemical Composition
Main Elements
- Nickel (Ni): Nickel is the base element of UNS N06625, with a
content of at least 58%. Nickel imparts excellent corrosion
resistance, especially in reducing environments. It also
contributes to the alloy's high - temperature strength and good
toughness, allowing the alloy to maintain its mechanical properties
at elevated temperatures. For example, in high - temperature
chemical processing, nickel helps the alloy resist attack from
various corrosive media.
- Chromium (Cr): The chromium content in UNS N06625 ranges from 20.0%
to 23.0%. Chromium is crucial for forming a dense and adherent
chromium - oxide film on the alloy surface. This film provides
outstanding oxidation resistance, protecting the alloy from high -
temperature oxidation and many corrosive substances. In
applications such as in the aerospace industry, where components
are exposed to high - temperature and oxidative environments, this
chromium - induced protection is essential.
- Molybdenum (Mo): With a content of 8.0% - 10.0%, molybdenum
significantly enhances the alloy's resistance to pitting and
crevice corrosion, especially in chloride - containing
environments. It also improves the alloy's strength at elevated
temperatures. In marine applications, where seawater contains high
levels of chlorides, the presence of molybdenum in the alloy
ensures long - term durability.
- Niobium (Nb) (plus Tantalum (Ta) when present): The combined
content of niobium and tantalum (usually niobium is the main
component, with a content of 3.15% - 4.15%) is important for
precipitation strengthening. Niobium forms fine carbide particles
during heat treatment, which enhance the alloy's strength,
especially at high temperatures. This is beneficial in applications
like gas turbines, where components need to withstand high -
temperature and high - stress conditions.
Minor Elements
- Carbon (C): The carbon content is limited to a maximum of 0.10%.
Excessive carbon can form carbides, which may reduce the alloy's
corrosion resistance, especially in sensitization - prone
environments. By keeping the carbon content low, the alloy can
maintain its excellent corrosion - resistant properties during
welding and in service.
- Silicon (Si) and Manganese (Mn): Silicon content is typically
limited to a maximum of 0.50%, and manganese content is also capped
at 0.50%. These elements play a role in the deoxidation process
during alloy production. While they are present in small amounts,
an excessive increase in their content could potentially affect the
alloy's mechanical and corrosion - resistant properties. For
example, too much silicon might cause brittleness in certain
circumstances.
- Phosphorus (P) and Sulfur (S): Phosphorus content is restricted to
a maximum of 0.015%, and sulfur content to a maximum of 0.015%.
These elements are considered impurities. High levels of phosphorus
and sulfur can lead to reduced ductility and an increased
susceptibility to hot cracking during processing. In extreme cases,
they can also negatively impact the alloy's corrosion resistance.
Mechanical Properties
Tensile Strength
The tensile strength of UNS N06625 nickel alloy round bar at room
temperature is typically around 830 MPa (120,000 psi). This high
tensile strength is crucial in many applications. In the aerospace
industry, for instance, components like aircraft engine parts are
subjected to extreme mechanical stresses during flight. The high
tensile strength of UNS N06625 ensures that these parts can
withstand the centrifugal forces, vibration, and thermal stresses
without breaking, thus maintaining the structural integrity of the
engine and ensuring the safety of the flight. In the construction
of high - pressure pipelines in the oil and gas industry, the
alloy's high tensile strength allows the pipelines to resist the
internal pressure of the transported fluids, preventing leaks and
ensuring the efficient transportation of oil and gas.
Yield Strength
The yield strength of UNS N06625 at room temperature is
approximately 415 MPa (60,000 psi). Yield strength represents the
stress at which the material begins to deform plastically. A
relatively high yield strength means that the alloy can resist a
significant amount of stress before permanent deformation occurs.
In marine applications, where structures such as offshore platforms
are constantly under the influence of waves, tides, and the weight
of the equipment on them, the high yield strength of UNS N06625
enables these structures to maintain their shape and dimensions
over long periods. This is essential for the safety and long - term
operation of the platforms, as any significant deformation could
lead to structural failure.
Elongation
The elongation of UNS N06625 nickel alloy is around 30%. Elongation
is a measure of the material's ductility, which is closely related
to its toughness and processing properties. A high elongation value
indicates good toughness, meaning the alloy can absorb a large
amount of energy before fracturing. This is beneficial in
applications where the material may be subjected to sudden impacts
or dynamic loads, such as in the manufacturing of shock - absorbing
components in machinery. In terms of processing, the good
elongation property allows the alloy to be easily formed into
various shapes through processes like forging, rolling, and
extrusion. For example, during forging, the alloy can be deformed
into complex shapes without cracking, enabling the production of
high - quality components with precise geometries.
Hardness
The hardness of UNS N06625 is generally in the range of HB 200 -
250 (Brinell hardness). This moderate hardness level gives the
alloy good wear resistance. In applications where the material is
in contact with other surfaces in relative motion, such as in
bearings or seals in chemical processing pumps, the hardness helps
to prevent excessive wear, ensuring a long service life. At the
same time, the moderate hardness also makes the alloy amenable to
machining. It can be easily cut, drilled, and milled to the
required dimensions and tolerances, which is important for
manufacturing components with tight specifications in industries
like precision engineering.
Equivalent Grades
- Inconel 625: This is perhaps the most well - known equivalent grade
for UNS N06625. Inconel 625 is a trademarked name by Special Metals
Corporation. It is widely recognized in the global market,
especially in the aerospace and high - end manufacturing
industries. The use of Inconel 625 in these industries has led to
its high - profile status, and many engineers and designers are
more familiar with this name when specifying materials for
projects. For example, in the design of aircraft engine components,
the name Inconel 625 might be more commonly used in the initial
material selection phase.
- 2.4856 (DIN Standard): In the German and European context, the
number 2.4856 is used to identify this alloy according to the DIN
standard. This numerical designation is part of the German
standardization system for materials, which is widely used in
European manufacturing, particularly in the automotive, machinery,
and chemical engineering industries. When sourcing materials in
Europe or dealing with European - based suppliers, the 2.4856
designation becomes crucial. It ensures that the correct alloy is
specified and supplied, adhering to the strict quality and
composition requirements of the DIN standard.
- NC22DNb (AFNOR Standard): In France, the alloy is known as NC22DNb
under the AFNOR (Association Française de Normalisation) standard.
This grade is used in various French and francophone industrial
applications, such as in the oil and gas exploration and production
projects in French - speaking regions. Understanding this
equivalent grade is essential for companies operating in these
areas or collaborating with French - based partners in the energy
and related sectors.
- GH3625 (Chinese Standard): In China, GH3625 is the corresponding
grade for UNS N06625. The Chinese market has a large demand for
high - performance alloys in industries like aerospace, power
generation, and petrochemicals. GH3625 is produced and used in
China, following the Chinese national standards. Chinese
manufacturers and end - users often refer to this grade when
specifying materials for their domestic projects.
Knowing these equivalent grades is extremely important in material
procurement and substitution. In the global market, different
suppliers may use different naming systems. When a company needs to
source UNS N06625 nickel alloy round bars, being aware of the
equivalent grades allows it to communicate effectively with
suppliers from different regions. For example, a company in the
United States may find a more cost - effective supplier in Europe.
By knowing the DIN - equivalent grade 2.4856, they can accurately
request the correct material. In terms of substitution, if a
particular grade is not available or has long lead times,
understanding the equivalent grades helps in finding suitable
alternatives that meet the project's requirements in terms of
chemical composition, mechanical properties, and product
standards.
Product Standards
ASTM Standards
ASTM (American Society for Testing and Materials) has several
standards relevant to UNS N06625 nickel alloy round bars. For
example, ASTM B446 covers the standard specification for nickel -
chromium - molybdenum alloy (UNS N06625) rod and bar. This standard
precisely defines the dimensions, tolerances, and mechanical
property requirements of the round bars. In terms of dimensions, it
specifies the allowable diameter ranges and length tolerances,
ensuring that the products are of a consistent size for various
applications. For mechanical properties, it sets minimum
requirements for tensile strength, yield strength, and elongation,
guaranteeing that the alloy bars can withstand the mechanical
stresses expected in their intended applications. Products meeting
ASTM standards are widely recognized and accepted in the American
market and are often specified in industries such as aerospace, oil
and gas, and chemical processing in the United States.
EN and DIN Standards
In Europe, the EN (European Norm) and DIN (Deutsches Institut für
Normung) standards play a crucial role. The EN standards for UNS
N06625 nickel alloy round bars focus on aspects such as chemical
composition control, mechanical property verification, and quality
management during production. They ensure that the alloy's chemical
composition adheres strictly to the specified ranges, which is
essential for maintaining its corrosion - resistant and mechanical
properties. The DIN standards, on the other hand, are more detailed
in some areas, such as heat treatment requirements and surface
quality inspection methods. For example, DIN standards may specify
the exact heat treatment processes, including temperature, time,
and cooling rates, to achieve the desired microstructure and
mechanical properties. European - made UNS N06625 round bars that
comply with these standards are highly regarded for their quality
and reliability, and they are commonly used in European - based
industrial projects, especially in the automotive, machinery
manufacturing, and energy sectors. These standards also take into
account environmental and safety aspects, ensuring that the
production and use of the alloy bars are in line with European
environmental protection and safety regulations.
GB Standards
In China, the GB (Guobiao, national standard) for UNS N06625 nickel
alloy round bars (corresponding to the Chinese grade GH3625) sets
out the technical requirements for the alloy. It includes
requirements for chemical composition, which must meet the
specified ranges to ensure the alloy's performance. The mechanical
property requirements in the GB standard are also clearly defined,
covering aspects such as tensile strength, yield strength, and
hardness. Additionally, the standard addresses inspection and
testing methods, packaging, marking, and storage requirements.
Products that meet the GB standards are well - suited for the
domestic market in China, as they are produced in accordance with
local industry needs and regulations. In the Chinese aerospace,
petrochemical, and power generation industries, where high -
performance materials are required, GB - compliant UNS N06625 round
bars are often preferred due to their quality assurance and local
availability.
Product Advantages
Corrosion Resistance
UNS N06625 nickel alloy round bars exhibit outstanding corrosion
resistance in a wide range of corrosive environments. In the
chemical industry, where exposure to strong acids, alkalis, and
various chemical reagents is common, this alloy can withstand the
corrosive effects of substances such as sulfuric acid, hydrochloric
acid, and sodium hydroxide. For example, in chemical reactors and
storage tanks, the alloy's corrosion - resistant properties ensure
that the equipment can operate safely for long periods without the
risk of leakage or structural failure due to corrosion. In marine
engineering, the high chloride content in seawater poses a great
challenge to the materials used. UNS N06625 can resist pitting and
crevice corrosion caused by chlorides, making it an ideal choice
for components such as ship hulls, offshore platform structures,
and seawater pipelines. Its ability to resist corrosion in marine
environments significantly extends the service life of these
structures, reducing maintenance and replacement costs.
High - Temperature Performance
One of the remarkable features of UNS N06625 is its excellent high
- temperature performance. At elevated temperatures, it can
maintain high strength and stability. In the aerospace industry,
components like turbine blades and combustion chambers in aircraft
engines are exposed to extremely high temperatures during
operation. The high - temperature strength of UNS N06625 allows
these components to withstand the thermal stresses and mechanical
loads, ensuring the efficient operation of the engine. In the
energy sector, such as in power plants, boilers, and gas turbines,
the alloy can endure high - temperature flue gases and steam,
contributing to the reliable operation of power - generation
equipment. Even at temperatures up to 800°C, UNS N06625 still
retains a significant portion of its room - temperature strength,
which is crucial for applications in high - temperature
environments where structural integrity must be maintained.
Weldability and Machinability
UNS N06625 nickel alloy round bars have good weldability, which is
of great significance in manufacturing processes. Welding is a
common method for joining components in various industries. The
good weldability of this alloy means that it can be easily welded
to other parts without significant issues such as cracking or
porosity in the weld joints. This reduces the complexity and cost
of manufacturing complex structures. For example, in the
construction of large - scale chemical processing plants, where
many pipes and vessels need to be joined, the good weldability of
UNS N06625 enables efficient construction and ensures the integrity
of the welded structures. In terms of machinability, the alloy can
be readily processed using common machining techniques such as
turning, milling, and drilling. This allows manufacturers to
produce components with high precision and complex geometries,
meeting the strict requirements of different industries. Good
machinability also increases production efficiency, as it reduces
the time and effort required for machining operations, ultimately
leading to cost savings in the manufacturing process.
Product Applications
Aerospace Industry
In the aerospace industry, UNS N06625 nickel alloy round bars play
a crucial role. For aircraft engine components, such as turbine
blades, the high - temperature strength and corrosion resistance of
UNS N06625 are essential. Turbine blades are exposed to extremely
high - temperature gas streams during engine operation, often
reaching temperatures well above 500°C. The alloy's ability to
maintain its mechanical properties at these high temperatures
ensures that the blades can withstand the centrifugal forces and
thermal stresses without deforming or failing. This is directly
related to flight safety, as any failure of the turbine blades
could lead to engine malfunction and potentially a catastrophic
accident. In addition, for aircraft structural components like wing
spars and fuselage frames, the high strength - to - weight ratio of
UNS N06625 is beneficial. It allows for the construction of lighter
yet stronger structures, which in turn improves fuel efficiency and
increases the aircraft's payload capacity. The alloy's corrosion
resistance also protects these components from the corrosive
effects of environmental factors such as moisture and pollutants in
the atmosphere, ensuring the long - term integrity of the aircraft
structure.
Petrochemical Industry
In the petrochemical industry, UNS N06625 nickel alloy round bars
are widely used in the manufacturing of pipelines, reaction
vessels, and valves. Pipelines in petrochemical plants often
transport highly corrosive substances such as crude oil, refined
fuels, and various chemical reagents. The excellent corrosion
resistance of UNS N06625 ensures that the pipelines can operate
safely for long periods without suffering from leaks or failures
due to corrosion. For example, in pipelines that carry sulfur -
containing crude oil, the alloy can resist the corrosion caused by
sulfur compounds, which are highly corrosive in the presence of
moisture. Reaction vessels, which are used for chemical reactions
under high - temperature and high - pressure conditions, require
materials with high strength and corrosion resistance. UNS N06625
meets these requirements, allowing the vessels to maintain their
structural integrity during the reaction processes. Valves in
petrochemical plants need to be able to withstand the corrosive
media and high - pressure flows. The use of UNS N06625 in valve
manufacturing ensures smooth operation and long - term reliability,
which is crucial for the stable operation of the entire
petrochemical production process. Any disruption in the pipeline,
reaction vessel, or valve system could lead to production downtime,
which is not only costly but also potentially dangerous due to the
release of harmful chemicals.
Marine Engineering
In marine engineering, the high chloride content in seawater poses
a significant challenge to the materials used. UNS N06625 nickel
alloy round bars are highly valued for their outstanding resistance
to seawater corrosion. For offshore platforms, which are constantly
exposed to seawater, wind, and wave forces, the alloy is used in
the construction of structural components such as support columns
and decks. Its high strength and corrosion resistance enable the
platforms to withstand the harsh marine environment and the
mechanical stresses caused by the movement of the sea. This ensures
the long - term stability and safety of the platforms, which are
essential for the extraction of offshore oil and gas resources. In
shipbuilding, UNS N06625 is used for manufacturing components such
as propeller shafts, rudder components, and seawater - handling
systems. Propeller shafts need to have high strength to transmit
the power from the engine to the propellers and also need to resist
the corrosive effects of seawater. The use of UNS N06625 in these
applications significantly extends the service life of the
components, reduces maintenance costs, and improves the overall
performance and reliability of the ships.
Other Fields
- Energy Field: In the energy field, especially in nuclear power
plants, UNS N06625 nickel alloy round bars are used in the
manufacturing of components such as reactor internals and heat
exchanger tubes. In nuclear reactors, the components are exposed to
high - temperature, high - pressure, and highly radioactive
environments. The alloy's high - temperature strength, corrosion
resistance, and radiation resistance make it suitable for these
applications. Heat exchanger tubes need to transfer heat
efficiently while resisting corrosion from the coolant. UNS N06625
ensures the reliable operation of the heat exchangers, which is
crucial for the safe and efficient generation of nuclear power.
- Medical Field: In the medical field, UNS N06625 is used in the
manufacturing of certain medical devices. For example, in some
implantable devices that require high - strength and biocompatible
materials, the alloy's properties make it a viable option. Its
corrosion resistance ensures that the device does not corrode in
the human body, and its mechanical strength allows it to maintain
its shape and function over time. Although the use in the medical
field is relatively limited compared to other industries, it still
plays an important role in the development of advanced medical
technologies, contributing to better medical treatment and patient
care.
Conclusion
UNS N06625 nickel alloy round bars, in both black bar and bright
bar forms, are a remarkable class of materials. Their carefully -
balanced chemical composition, featuring high nickel, chromium,
molybdenum, and niobium contents, endows them with outstanding
corrosion resistance, high - temperature strength, and good
toughness. The mechanical properties, such as high tensile and
yield strengths, decent elongation, and moderate hardness, make
them suitable for a wide range of applications. The existence of
multiple equivalent grades under different standards and the
compliance with various product standards (ASTM, EN/DIN, GB) ensure
their availability and quality control in the global market.
The product advantages of UNS N06625, including excellent corrosion
resistance, high - temperature performance, and good weldability
and machinability, have led to their extensive use in critical
industries like aerospace, petrochemical, and marine engineering.
As industries continue to evolve and demand materials that can
withstand more extreme conditions, UNS N06625 nickel alloy round
bars are expected to play an even more significant role. With the
continuous development of manufacturing and processing
technologies, it is likely that the performance of these alloy
round bars will be further optimized, opening up new application
possibilities in emerging fields such as advanced energy
technologies and high - tech manufacturing.
Monel 400 Alloy Sheet Plate UNS N04400 Nickel Alloy ASTM B127
