Feature Article
SCHMOLZ + BICKENBACH GROUP
Internal combustion engine:
Special steels lower emissions and
fuel consumption
Average CO2 emissions for automobiles are to be lowered from
130 g to 95 g per kilometre by 2020 to meet European Commission
standards. Alternative drive concepts are gaining ground. The
classic internal combustion engine, however, is a long way from
disappearing, not least of all because it still has great potential for
improvement. To comply with the emission standards, downsizing
is one of the development targets of the automotive industry: Cubic
capacity and cylinders of diesel and gasoline engines are
becoming smaller overall, but they are expected to remain just as
powerful. The key to fuel-efficient and environmentally friendly
engines is a higher degree of efficiency which can be provided by
direct injection and turbochargers that supply the optimum amount
of air and fuel to the combustion chamber under high pressure. At
pressures of up to 3,000 bar and temperatures in some cases of
over 1,000 °C, modern steel materials are called for that are
particularly resistant to heat and pressure, retain their shape, and
demonstrate fatigue strength under vibration stresses. One
producer of innovative long steel solutions is the SCHMOLZ +
BICKENBACH GROUP.
In the discussion on the improvement of vehicle efficiency, for example,
through lightweight construction, the focus is often on flat steel products.
Yet high-strength and ultra-high-strength long steel products are also
needed to reduce fuel consumption and pollutants: without special steels
the
high-performance
systems
such
as
direct
injectors
and
turbochargers would be inconceivable. These materials what make
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downsizing the internal combustion engine and thus sustainable mobility
possible in the first place. Direct injection has become the main
technology used both in gasoline as well as diesel engines due to the
precise metering of fuel. Depending on the fuel type, the requirements
on the materials used in these systems vary greatly. In the gasoline
engine, heavily stressed components such as the high-pressure pump,
fuel rail, injection valves and connectors need to be especially resistant
to corrosion. "Gasoline is very aggressive. That's why the steel's sulphur
content was reduced to a minimum for the high-pressure pump case.
This increases its resistance to corrosion and prevents cracking along
the welded seams," explains Manfred Maslow, Sales Manager
Automotive Stainless at Deutsche Edelstahlwerke GmbH, one of the
companies of the SCHMOLZ + BICKENBACH GROUP. Using special
melting and rolling processes as well as selective heat treatment, the
degree of purity and fine-grained structures are also improved. The
steels Acidur 4057, Acidur 4418 and Acidur 4301 are ideal for these
applications. Deutsche Edelstahlwerke has optimized Acidur 4057
specifically for welding applications and for the increasing demands, as it
has the other two steels.
In the injecton valve, it's all about the magnetic properties. To be able to
regulate the efficient injection of fuel as the valve opens and closes, the
material used for the valve needs to be electromagnetically actuated.
Only a few steel producers have the expertise to produce the required
magnetic properties accurately. The secret is selective heat treatment.
The correct processing of the steel also plays an important role since the
magnetic values are sensitive to mechanical action. In UGIPERM12FM,
Ugitech, another SCHMOLZ + BICKENBACH GROUP subsidiary, has
introduced a suitable material to the market: the steel combines
optimized magnetic properties with good machinability which in turn
allows easier fabrication and thereby reduces cycle times for the
customer.
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The challenge for connectors in the fuel injection system is tightness and
purity as well as the strength of the material. One example is the
connectors used on the distribution pipe of the high-pressure rail, the
fuel accumulator between the high-pressure pump and injection nozzle.
To withstand aggressive gasoline and avoid leakage, pure, corrosionresistant and mechanically strong steels are needed. "We recommend
Duplex steels from our UGIPLEX series for these applications," says
Raphael Craen, Automotive Sales Director at Ugitech. "Compared to
standard steels, they contribute to better corrosion resistance and good
mechanical properties. With fewer alloying elements these steels are
also interesting in terms of price."
High degree of purity for diesel engines
The demands placed on components in diesel engines are more
extreme than in gasoline engines due to the higher ignition temperature.
While the injection system in gasoline engines is subjected to pressures
of up to 300 bar, the long-term development in diesel engines is edging
towards 3,000 bar. This also increases the demands attendant on
downsizing, requiring the use of bar steels with higher static and
dynamic strength as well as a higher degree of purity. Even the smallest
material inclusions could cause the component to fail given the high, in
part changing loads exerted on it.
The purer the steel is, the higher forces it can withstand even at small
component diameters. One highly stressed component is the injection
nozzle that supplies fuel directly to the combustion chamber. The steels
used in these components have to hold up under extremely high
temperatures. "This is where our Carbodur 5920 (18CrNi8) comes in. It
remains stable at high temperatures and under high pressure," reports
Ralf Schneider, Sales Manager Stainless Steel and Automotive at
Deutsche Edelstahlwerke GmbH. The material gets its high degree of
purity from an electro-slag remelting process (ESR). In this process, the
ingot is immersed in liquid slag and remelted when an electric current is
applied. As it passes through the slag, the steel is refined: impurities and
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oxides are bound in the slag. The remelting process takes place in a
water-cooled mould so that the ingot solidifies uniformly.
For thin-walled components subjected to high stresses the SCHMOLZ +
BICKENBACH GROUP offers ESR in a protective gas atmosphere at
their steel mills. This produces an even higher degree of purity. This
material is needed for the delicate nozzle body, for example. Firmodur
7228 (50CrMo4) from Deutsche Edelstahlwerke is ideal as a modified
tempered steel for the increasing stresses of these applications.
For the high-pressure common rail in diesel engines Deutsche
Edelstahlwerke has improved the standard stainless Microdur 5231
(38MnSiVS6+NB) by adding Niobium, thereby increasing its fine grain
stability. Users profit from greater strength, better cleanliness and
pressure tightness. The machinability of the forged part is not hampered
by the high strength.
High and higher strength steels for the common rail system
The components used in common rail technology, the current standard
for diesel engines, are also subject to high stresses. Components such
as nozzle and magnetic clamping nuts hold the system together even at
pressures above 2,000 bar. High and higher strength grades are needed
for the components to withstand changing loads. In addition to dynamic
strength, the steel used to produce the clamping nuts must also be easy
to machine. "We manage the balance with ETG 100 and HSX 110,"
explains Dirk Ochmann, Sales Manager at Steeltec AG, a company of
the SCHMOLZ + BICKENBACH GROUP. "The special steels are hot
drawn and compared to tempered steels combine the apparently
contradictory properties as-delivered." This saves additional machining
steps and thus time and money.
Steeltec also has an alternative for magnetic applications like the highpressure solenoid valve. ETG 25 is easy to weld and machine compared
to conventional soft magnetic materials - important criteria for the
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efficient machining of turned parts. As a special steel, it is ideal for the
compact designs generally needed for downsizing. Components can
also be manufactured more affordably in regard to the overall process
chain.
High boost pressure in superchargers
Engine dynamics are directly linked to the boost pressure produced in
the supercharger. As an important element of downsizing strategies, the
turbine utilizes exhaust gas energy to compress intake air and inject it
into the combustion chamber under high pressure. This produces
temperatures of up to 1,000 °C. Heat-resistant steels are in demand for
this application, such as UGI 4845 and UGI 4828 from Ugitech. These
steels are also used to manufacture sleeves as well as fasteners that
hold the turbine together. With this in mind, the steel producer
guarantees the input stock's high straightness and dimensional
accuracy, thereby also guaranteeing precise, non-warping component
manufacture and the safe functioning of the component.
The thin-walled sealing sleeve in the compressor is subjected to
alternating stresses. The sleeve seals the bearing case against hot
exhaust gases from the turbine and keeps it from losing oil. Long steel
products with low internal stresses are needed to be able to manufacture
dimensionally stable components even at different stresses. Since a
large amount of material is removed during manufacture of the sealing
sleeves, ETG 100 is recommended for optimum machining results. To
ensure that the material strength does not fail at system temperatures of
up to 200 °C, Steeltec subjects the material to a preliminary shaping
step during manufacture.
Automotive manufacturers use camshaft phasing units, camphasers, for
downsizing to improve efficiency during change of the cylinder charge.
They control the opening and closing of the valves. The special
demands placed on the part are the transverse loads due to lateral and
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shearing stresses. Camphasers are fitted into the engine in the
micrometer range and consequently the alignment dimensions and
delicate borings must be exact. A low-distortion material with low internal
stress is needed. With its homogeneous structure, HSX Z12 is ideal for
uniform component design. The mechanical parameters of the special
steel from Steeltec AG help it withstand dynamic stresses better than
other tempered steels.
Summary
The direct injection system and supercharging are important parts of the
automotive industry's downsizing strategy to reduce the emission of
pollutants and cut fuel consumption. Components are becoming more
compact, but still have to withstand higher forces and temperatures.
With their own steel mills, technical know-how and state-of-the-art
process and testing technologies, the SCHMOLZ + BICKENBACH
GROUP can modify long steels to meet the stricter requirements of the
automotive industry and make a contribution to the car of the future.
Length:
10680 characters plus spaces
Status:
7 April 2014
Picture 1: How an internal combustion engine works (©iStockphoto
– SCHMOLZ + BICKENBACH)
Picture 2: Supercharger (© Alterfalter – Fotolia.com)
Picture 3: High-pressure common rail for the direct injection of
gasoline
Picture 4: Electro-slag remelting plant
Picture 5: Steel drawing plant
Picture 6: Quality assurance system
Caption 1: The injection nozzle in the IC engine is a highly stressed
component that injects fuel under high-pressure into the combustion
chamber.
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Caption 2: Numerous long steel products hold the supercharger
together to provide efficient air intake into the combustion chamber.
Caption 3: High-grade, corrosion-resistant and mechanically stable
steels are needed for the connectors on the high-pressure common rail.
Caption 4: Sulphur and non-metallic inclusions are filtered out of the
steel during remelting. This gives the material an especially high degree
of purity.
Caption 5: The ETG 100 and HSX 110 special steels from Steeltec AG
develop their high strength properties during the hot drawing process.
Caption 6: To meet the highest standards of quality, the SCHMOLZ +
BICKENBACH GROUP tests their steel products on state-of-the-art test
stands.
About SCHMOLZ + BICKENBACH
The SCHMOLZ + BICKENBACH GROUP is one of the world’s leading providers of
special high-grade steels. The GROUP is one of the leading producers on the global
market both in tool steels as well as for stainless long steels and is one of the three
largest companies in Europe for alloy and high-alloy special and engineering steels. With
circa 10,000 employees and its own production and distribution companies in more than
35 countries on five continents, the company guarantees its customers global support
and supply and offers them the entire portfolio consisting of production and Sales &
Services at locations worldwide. Customers benefit from the technological expertise of
the company, the same high product quality around the world, as well as a detailed
knowledge of local markets.
About Deutsche Edelstahlwerke GmbH
Deutsche Edelstahlwerke GmbH is one of the leading manufacturers of long high-grade
steel products worldwide with over 150 years of experience. The product range
unrivalled around the world comprises tool steel, stainless, acid, and heat-resistant steel,
high-grade construction steel and special materials. The range of dimensions extends
from drawn steel 0.8 mm in diameter as well as forged products 1,100 mm in diameter.
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Customers of Deutsche Edelstahlwerke get the complete production chain from a single
source: from manufacture and prefabrication to finishing with heat and surface treatment.
About Steeltec AG
Steeltec AG is one of Europe’s leading manufacturers of bright steels. With a focus on
high-strength and higher-strength special steels and special free-cutting steels, Steeltec
has an establish position as an important partner to the automotive and hydraulic
industries and the mechanical engineering sector. Steeltec works closely with
customers, suppliers and research institutions to continually improve the production and
engineering properties of steel, driving competitiveness across the entire value chain.
Working within these partnerships, Steeltec develops high-performance steel solutions
that meet its customers’ application needs.
About Ugitech S. A.
Ugitech is one of the leading manufacturers of stainless steel long products worldwide.
The company's main products include billets, bar stock, wire rod, drawn wire that the
company produces in its own steel mill and in its rolling mills and wire-drawing plants.
The stainless steels are known for their excellent mechanical properties. They are used
to manufacture a wide range of parts, such as e.g. valves, turbine components, welding
wire or surgical instruments. With over 100 years of experience in steel production and
ongoing metallurgical research, the company guarantees optimum steel solutions for
demanding applications for its customers in the automotive, construction, process and
aviation industries and medical technology.
Corporate Contact
Dr. Andreas Knaut • SCHMOLZ + BICKENBACH GROUP
Director Corporate Communications and Marketing
Phone (CH): +41 (0)41 209-5032 • Fax (CH): +41 (0)41 209-5033
Phone (D): +49 (0)211 509-2067 • Fax (D): +49 (0)211 509-1067
E-Mail: a.knaut@schmolz-bickenbach.com
Internet: www.schmolz-bickenbach.com
Contact Deutsche Edelstahlwerke GmbH
Melanie Biskup
Phone: +49 (0) 2302-292216 • Fax: +49 (0) 2302-2 94-9 78
E-Mail: melanie.biskup@dew-stahl.com • Internet: www.dew-stahl.com
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Contact Steeltec AG
Petra Hausmann
Phone: +49 (0) 7728-649 152 • Fax: +49 (0) 7728-825
E-Mail: petra.hausmann@steeltec.ch • Internet: www.steeltec.ch
Contact Ugitech S. A.
Frédérique Tissot
Phone: +33 (0) 47989-3012 • Fax: +33 (0) 47989-3434
E-Mail: frederique.tissot@ugitech.com • Internet: www.ugitech.com
External media contact
Hanna Maurer • additiv pr GmbH & Co.KG
Public relations for logistics, steel, industrial commodities and IT
Herzog-Adolf-Straße 3 • D-56410 Montabaur
Phone: +49 (0)2602 95099-15 • Fax: +49 (0)2602 95099-17
E-Mail: hm@additiv-pr.de • Internet: www.additiv-pr.de
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