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STEEL BARS
FOR
AUTOMOTIVE
Steel bar applications in automotive
engines and drive trains must
meet stringent requirements for
micro-cleanliness and machinability,
in addition to tightly controlled
chemistry and hardenability.
John Bayer*
MacSteel
Jackson, Michigan
*Member of ASM International
• Constant Velocity Joints (CVJ) are integral to most all drivetrains,
especially those involving front or all-wheel drives. The majority of CVJ’s
are produced from 0.45 - 0.55%C grades on multi-stage warm form
presses. CVJ products are also produced from low carbon, alloy carburizing grades, and can be cold formed or hot forged. The warm or cold
formed parts are generally produced from bar that has been machine
turned or cold drawn to allow for near net shaped parts in these closed die
operations. The low carbon parts are carburized, and the shafts of these
parts are induction hardened.
• Drive train shafting and axles are
generally produced from either a hotrolled or turned, cold-finished bar with
carbon ranging 0.40 to 0.60%. Some
shafting/axle product may require
minor alloying, depending on
strength requirements. Drive axles
may be produced with hot upsetting for flanges and with machined splines.
• Camshafts are generally produced from hotrolled bar with a cold-finished surface that has been
machine-turned. The majority of steel camshafts are produced by machining, with no prior metal forming. Both
carbon and alloy grades are suitable, but most machined
camshafts are produced from grade 1045 – 1060 steel with
elevated sulfur (0.035-0.050%) to enhance machinability.
Bar product is generally normalized and machined-straightened prior to camshaft manufacturing. This allows for consistent microstructure and straightness, which improves
both the machining and induction hardening processes.
The 0.50% carbon level allows for excellent surface wear
resistance on both bearing journals and cam lobes. In addition, the high strength allows some manufacturers to
center-drill for hollow camshafts, thus reducing weight.
High-performance racing camshafts are produced from
low-carbon alloy grades that provide higher strength and
fatigue life. Furthermore, these parts are carburized to
provide a higher surface hardness for enhanced wear
resistance.
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A P P L I C AT I O N S
M
ost automotive powertrain applications require specific steel properties
that mandate very tight control of
manufacturing techniques. As a result, steelmaking practices must have high levels
of repeatability and process control to meet stringent micro-cleanliness requirements. In addition,
chemical composition and ranges must be tightly
controlled to meet hardenability, machinability,
and grain size requirements.
High-strength steel bars are specified for
camshafts and crankshafts in today’s smaller, more
highly powered engines and drivetrains because
they provide required formability, strength, and
fatigue resistance. This article describes the composition, properties, and applications of high
■
strength steel bars.
• Differential, side, and pinion gears are generally produced from 0.15 to 0.27%C, low alloy steel,
and are carburized after manufacture. Larger gearing
can be made of a medium carbon alloy that is throughhardened prior to machining. Grade selection depends on the specific application, but it also should
be related to any “mating” parts so that wear
and strength characteristics may be
matched.
• Crankshafts are most often
produced from medium to high carbon
grades with elevated manganese (15xx
grades). Additionally, vanadium or boron may be
added to provide higher strength. These parts are hot forged, and
may be twisted during forging for alignment. The journals for both
the main and connecting rod bearing surfaces are induction hardened before final grinding. These higher strength steels provide for
smaller, lighter weight crankshafts that still meet the higher torque
requirements for smaller, more powerful engines.
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Effects of common alloying elements in automotive steels
Element
Effects
Carbon
The principal strengthening element in steel. It can have a great effect on numerous metallurgical properties.
Increased carbon levels can provide increased hardness and strength. Lower carbon (less than 0.25%) improves
weldability, ductility, and toughness at the expense of strength.
Alloying elements have a major impact
Increases strength and toughness. Manganese has one of the strongest
on properties of steel and the subsequent
elemental effects on steel’s hardenability (the ability of steel to harden at
costs of part manufacture. As every engia depth from the surface through quenching). Higher levels have a
neer knows, the goal is to develop a steel
negative effect on weldability.
chemistry that will meet all the required
Considered an impurity, except when intentionally added to improve
objectives with the most cost-effective
machinability. It combines with manganese to produce manganese
manufacturing process.
sulfide (MnS) inclusions, which assist as “chip breakers” in machining
The sulfur level of steels provided for
steels. Higher sulfur levels have a detrimental effect on impact resistance. many powertrain applications is generally elevated to a level to provide maxA deoxidizer, it is added to steel to tie up free oxygen. The term “killed
imum machinability without negatively
steel” is used when it is deoxidized, thus providing improved internal
impacting product performance. The
soundness and surface quality. Higher levels slightly increase
hardenability (the ability of steel to develop
hardenability; however, silicon can have a negative impact on
a specific hardness level at a depth from
machinability.
the quenched surface) is generally tightly
Table continues on next page
controlled through chemistry. This allows
the engineer to define specific strength and
toughness criteria based on the needs and
geometry of the part.
Manganese
Sulfur
Silicon
• The majority of transmission
main and counter shafts, in addition
to input and output shafts, are produced
from medium carbon grades (0.40 to
0.55%C) and are cold or warm formed.
These shafts have spline gearing that is cold
roll formed or machined, then induction
hardened. Transmission and transfer case
gearing consists predominantly of alloy carburizing steel that is warm or hot forged, surface
hardened, and machined.
• Smaller shafting for Constant
Velocity Joints (CVJ) is generally cold
drawn bar product with rolled splines. The
spline gearing area of drive shafts is predominantly induction hardened. Shafting,
like gearing, requires machinability, and
shafts must be able to develop specific
strength, fatigue, and wear properties after
surface hardening or heat treatment.
• Yokes are predominantly hot forged from 0.35 to 0.45%C grades, much of which may be
resulfurized (11xx series) to improve machinability. Yoke ears are machined, and the spline
gearing may be machined or formed on either the ID or OD of the shaft. After machining, these
parts are induction hardened. Yokes may be friction welded to longer shafting (solid or hollow)
if required, or mated with hollow aluminum drive shafting for weight reduction. Yoke spiders
are generally produced from low carbon, carburizing alloy grades. They are then warm formed for
net or near net shape control before hardening and final grinding.
• Hubs and spindles (wheel bearings) are produced from higher carbon (>0.50%), bearing quality
steel. These parts are hot forged, induction hardened,
and machined. New generation wheel bearings have
bearing races that are not external, but instead are designed into the part. This requires a machined and
ground, hardened raceway, hence the steel cleanliness is critical.
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Effects of common alloying elements in automotive steels, continued
Element
Effects
Nickel
When combined with other alloying elements, it produces steels with excellent strength and low-temperature
toughness in the quenched and tempered condition.
Chromium
Provides wear resistance, hardenability, and low temperature toughness. At high levels, it provides corrosion and
oxidation resistance, and assists in maintaining strength levels at elevated temperatures.
Molybdenum
Has a strong effect on hardenability (similar to manganese). Molybdenum also increases strength at elevated
temperatures.
Aluminum
Acts as a deoxidizer and helps control grain size. It can have a negative impact on machinability.
Columbium
(Niobium)
Helps produce fine grain steel, and improves the strength of micro-alloyed steels.
Vanadium
Also helps produce fine grain steel. Additionally, it can be used to increase strength, impact toughness, and
hardenability. Vanadium can have a negative impact on machinability.
Titanium
Primarily a deoxidizer and nitrogen scavenger in the making of boron steels. Also acts as a grain refiner. Titanium
can have a detrimental effect on machinability.
Boron
Increases hardenability in steel with less than 0.80% carbon, replacing other alloying elements.
Common bar steel grades: properties and applications
Carbon grades
Grade
Key properties
Typical applications
1016-1025
Carburizing steel with considerably better machining
characteristics than more formable lower-carbon steels.
Recommended for die forging and hot upsetting.
Commonly selected for low-strength-fastener
applications. Widely used for inexpensive massproduced carburized parts; popular carburizing steel.
Can be strengthened by cold working or surface
hardened by carburizing or cyaniding. Relatively
soft. Good weldability and formability.
1030
On the low end of the medium carbon types. Selected
instead of low-carbon steels where higher mechanical
properties are needed. Its hardness and strength can
be increased by heat treatment or cold working.
1038
1137
1141
Offers advantages in notch toughness . Response to
hardening is well suited for applications requiring
some machining in the quenched and tempered
condition. Strength can be increased either by hardening
or by cold drawing. Response to die forging and hot
upsetting is excellent.
Better mechanical properties than 1038, due to higher
carbon. Response to hardening is well suited to
applications that require machining in the quenched
condition. Strength is increased by hardening or cold
drawing. Good for normal machining operations.
Readily forged, formed, and upset at elevated
temperatures. Extensive deformation at room
temperatures is not recommended. Combines strength
with moderate resistance to abrasion and wear in the
heat-treated condition. Response to hardening is excellent.
Superior response to hardening by heating to the
appropriate temperature and quenching in either water or
oil. When quenched and tempered, moderately tough and
resistant to cracking and fatigue-type failure. Superior
forging characteristics.
1045
1050-1060
1070
48
Very suitable for carburized parts that require considerable cold forming. Camshafts, bearing retainers, and
chain rollers are typical parts that are carburized.
Low-strength bolts, nuts, rivets, tie rod ends, and a
variety of general hardware are among the products
that are not carburized. Cold-extruded piston pins.
Widely used for low-strength bolts and cold-formed
parts. Used in the case-hardened condition for
internal-combustion engine parts where cold strength
is not critical.
Very suitable for small parts of moderate strength.
Used for parts that are cold headed; before cold
heading, it is usually spheroidize annealed to improve
workability. Popular for gear and sprocket production.
Camshafts, tie rods, wheels, hubs, and other similar
applications.
Widely used in medium-strength, heat-treated forgings
intended for a variety of components. Crankshafts,
hubs, connecting rods, steering arms, axles, camshafts,
couplings, yokes, and gears are typical applications;
selection depends primarily on strength requirements,
details or fabrication and processing, and cost.
Used for a variety of medium-to-high-strength
heat-treated forgings in automotive applications.
Frequently cold-drawn to specified mechanical
properties for use without heat treatment in some
applications.
Widely used for medium-strength, forged parts and
accessories, particularly those requiring good torsional
strength and some abrasion resistance. Typical
automotive applications include camshafts, CVJs, and
input/output shafts.
Used for springs, and a variety of parts requiring good
fatigue resistance, moderate toughness, and resistance
to mechanical shock. In spring applications, grade 1070
is preferred for lighter sections and lighter loads,
whereas grade 1080, because of higher hardenability
and strength, can be employed where heavier sections
are required. Used for integrated wheel bearings –
hubs & spindles. Good for induction hardening in
applications requiring a relatively thin, hard case for wear
resistance augmented by a strong core for load-bearing
and shock resistance. Widely used in the manufacture of
case-hardened shafts and gears.
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Common bar steel grades: properties and applications, continued
Grade
Key properties
Typical applications
Carbon manganese grades
1522
Especially suited to heat treating by either normalizing or
Increasingly popular as an automotive gear steel, for
quenching in water and tempering to reasonably highapplications such as pinions and side gears. Can be
strength levels. Can be carburized for high surface hardness. carburized by the various methods.
1541
Responds in much the same manner as an alloy grade in
that through-hardening can be obtained in limited sections
and uniform strength levels can be engineered into the
finished component. Can be induction hardened.
Suitable for complex automotive transmission
component shafting where splines and gears are an
integral part of the shaft. Used for automotive
connecting rods.
1552
Higher carbon level provides higher surface hardness.
Automotive axle components where the material can be
induction hardened to high surface hardness and
uniform high-strength level can be maintained through
the balance of the cross section.
Through-hardening alloy grades
4140
Slightly difficult to process, is rarely cold formed but rather
forged or machined. Used in Q&T or N&T condition.
Can be heat treated to a high-strength level over a wide
range of sizes. Has good toughness.
Heavy gears, piston rods, heavy-duty crankshafts.
Can be used for demanding applications requiring high
strength and toughness
4340
Readily hot forged. Should be full annealed for machining,
spheroidize annealed for cold forming. Used in Q&T or
N&T condition.
Used for large industrial gears . Used for shafting,
piston rods.
5140
Should be fully annealed to facilitate machining. Should be
spheroidize annealed for cold forging or extruding. Used
predominantly in the Q&T or N&T condition.
Gears, light shafting.
8640
Readily hot forged. Should be fully annealed for machining, Industrial gears, automotive ball studs.
spheroidize annealed for cold forming. Used in Q&T or
N&T condition.
Carburizing alloy grades
4027
Can be hot forged. Can be machined in the as-rolled
condition. Can be cold forged to a limited degree. Higher
core hardness than the usual gear steel compositions.
Used for carburized gears in automotive applications.
4118
Can be hot or cold formed. Can be machined without prior
annealing. Carburized by conventional methods
Used principally for automotive carburized gears
subjected to moderate loading.
4320
Similar to 4620 in forging and other processing. Has higher
hardenability than 4620. Good for carburized gears for
heavy loading.
Widely used for carburized bearings.
4620
Can be forged similarly to the other carburizing grades.
Generally requires thermal treatment to facilitate cold
forming or machining.
Excellent for gears for moderate and heavy-duty
applications.
AISI Grade
Designation System
The American Iron &
AISI System of designations for commonly used grades
Steel Institute (AISI), the
Grade
Grade
American Society for
designation Steel Types
designation Steel Types
Testing and Materials
(ASTM), and the Society
10xx
Carbon Steel Grades
51xx
Chromium 0.80, 0.95 or 1.05 %
of Automotive Engineers
11xx
Resulfurized Carbon Steel Grades
51xxx
Carbon 1.00 % - Chromium 0.50, 1.00
(SAE) provide standards
or 1.45 %
for general specifications
12xx
Rephosphorized and Resulfurized
when ordering steel.
Carbon Steel Grades
86xx
Nickel 0.55 % - Chromium 0.50 % However, it should be
Molybdenum
0.20
%
13xx
Manganese 1.60 to 1.90 %
noted that very little bar
87xx
Nickel 0.55 % - Chromium 0.50 % 15xx
Manganese 1.00 to 1.35 %
steel for automotive apMolybdenum 0.25 %
plications is supplied to
23xx
Nickel 3.50 %
93xx
Nickel 3.25 % - Chromium 1.20 % general requirements.
33xx
Nickel 3.50 % - Chromium 1.55 %
Molybdenum 0.12 %
40xx
Molybdenum 0.25 %
94xx
Manganese 1.00 % - Nickel 0.45 % Chromium 0.10 % - Molybdenum 0.12 %
41xx
Chromium 0.95 % - Molybdenum 0.20 %
For more information:
97xx
Nickel 0.55 % - Molybdenum 0.20 % 43xx
Nickel 1.80 % - Chromium 0.50 or
John Bayer, MacSteel,
Chromium 0.17 %
0.80 % - Molybdenum 0.25 %
One Jackson Square
Jackson, MI 49201
46xx
Nickel 1.80 % - Molybdenum 0.25 %
98xx
Nickel 1.00 % - Chromium 0.80 % tel: 517/782-0415
Molybdenum 0.25 %
48xx
Nickel 3.50 % - Molybdenum 0.25 %
e-mail: jbayer@macsteel.com
Web site: www.macsteel.com.
50xx
Chromium 0.30 or 0.60 %
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