Recommedation Tech |
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Air-cooled bainite steel |
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Properties
and applications of five bainite steels |
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Low carbon granular bainitic steel
Professor Hongsheng Fang
has proved that good combination of strength
with toughness can be obtained by controlling
the size, quantity and distribute of the M/A
islands in granular bainite microstructure.
A kind of granular bainitic
steel was developed and became a new kind
of non-modified steel. After the process of
"forging or rolling-aircooling-medium
temperature temperin" this type of steel
can substitute for medium carbon alloy modified
steel and can be used in modified articles
such as auto front axles, bogies and connecting
rods.
This kind of granular
bainitic steel without quenching has been
used to manufacture sucker rods for many oil
fields in a large amount. The following properties
can be obtained:σ0.2-850MPa,σb-1100MPa,δ5,ψ
and αkuⅿJ/cm2.
Low carbon air-cooled
bainitic steel can be steadily used as bainite-type
non-modified steel.
Grain boundary allotriomorphic ferrite/granular
bainite dual phase steel( FGBA/Bg)
On condition that the
supplementary refinement, controlled rolling
technique, heat treatment and precious alloying
elements are not used, air-cooled low carbon
FGBA/Bg steel plates with thickness of 12mm,
16mm, 20mm can be successfully manufactured
in steel plate production line and they have
the following properties:σbMPa,σ0.2MPa,δ5,αku
value of 60J at 20‿and αku value of 27J
at -40᾿br>
This product has been
tested and used in many units and the results
indicate that it has advantages such as high
strength and toughness, good wear resistance
and excellent welding property, thus it has
a bright prospect in large amount and wild
area construction machinery. Besides being
used in medium and heavy steel plate, this
kind of steel also can be used in large gauge
and high strength ribbed bars, bainite-type
non-modified sucker rod, standard parts, plastic
mould and so on.
Medium and medium high carbon lower bainite/martensite
dual phase steel
The lower bainite/martensite
microstructure can be obtained from medium
carbon bainitic steels containing manganese
by aircooling. The strength and toughness
of this kind of steel is inferior to that
of single martensitic steel when tempered
at low temperature, but after tempering at
440₿it exhibits superior strength and toughness
compare with tempered martensite with identical
hardness.
This kind of steel is
applicable to most kinds of modified articles
or surface induction heating hardening articles
such as axle, cam shaft and crank shaft, etc.
This kind of air-cooled bainitic steel has
been successfully developed, for example,
the spring steel, which is used to make leaf
spring and spiral spring.
Carbide-free bainite/martensite (CFB/M) dual
phase steel
The carbide-free bainite/martensite
microstructure with ultra-fine structure can
be obtained in aircooled condition when silicon
is added to the bainitic steels containing
manganese. The former austenite grains are
divided and the martensite is refined by carbide-free
bainite plates, and thus the strength and
toughness of steel are improved.
Up to now, low carbon
CFB/M dual phase steel has been used to produce
ultra-high strength structural articles such
as high strength bolt, railway frog, high
strength steel plate and seamless tube, etc.
Medium carbon CFB/M dual phase steel can be
used for making different kinds of spring,
and medium-high carbon CFB/M dual phase steel
can be used for making wear-resistant articles
and grinding ball, etc.
Low and medium bainitic cast steel
Since bainitic steel is
a kind of high hardness and toughness steel,
air-cooled bainitic steel containing manganese
has been used to manufacture various wear-resistant
articles, such as grinding balls, casting
tubes and other mining articles. On the basis
of previous achievement in theoretical study
and application, Professor Hongsheng Fang
and his research team have developed several
novel high silicon content bainitic cast steels
and RE and titanium modified bainitic steels.
The results show that the high silicon content
and RE/Ti modification are effective for improving
hardness and toughness of bainitic cast steels.
These methods have been used in wear-resistant
bainitic cast steels production successfully.
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