abrasive and impact-abrasive wear testing of steels for mining, transporting, and minerals...
TRANSCRIPT
Abrasive and impact-abrasive
wear testing of steels for
mining, transporting, and
mineral processing
Hard rock tribology seminar
4.11.2014
Vilma Ratia Tampere University of Technology,
Tampere Wear Center,
Tampere, Finland
Contents
• Wear – what is it?
What are wear resistant steels?
• How can wear resistance be controllably
measured?
• How wear is shown in steels?
• Which factors affect wear of steels?
The durability of machinery in raw
materials extraction and processing is
increasing in importance
geosyntheticsmagazine.com
ruukki.com
ruukki.com
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Wear resistant steels have higher
strength and hardness than
conventional structural steels
• Commonly graded
according to hardness
in Brinell scale:
400HB, 500HB, 600HB
• Tensile strength
typically 1200-1600
MPa
• Notch impact energy at
-40C typically 30 J/cm2
• Microstructure often
martensitic, but bainite,
ferrite, pearlite and
austenite are also
possible
ruukki.com
N. Ojala et al. WTC 2013 & Wear 317(2014)225-232
Wear resistant steels can be used in a
wide range of applications
Examples of
applications:
• Agriculture
(harvesters, ploughs)
• Earth moving
(tippers, excavator
buckets)
• Forestry
(frost and rock
rippers, stump
processors)
• Mining
(wheel loader
buckets, stock pile
conveyors, sieves,
conveyor belt
hoppers)
johndeeredistributor.fi
deere.fi ruukki.com
sandviktamrock.fi
• Impeller (samples) 700 rpm
• Tumbler 30 rpm
• 900 g of granite(10-12,5 mm)/15 min • Altogether about 3-22 kg
• Sample size 75 x 25 x 10 mm
• Sample angle 30°, 60° or 90°
• Test duration 45-360 min
Impeller-tumbler simulates wear in
hammer mills, silos, loading of tippers
• Impeller-tumbler combines
impacts and abrasive wear
Wear testing enables the evaluating
of materials’ wear performance in
controlled conditions
metso.com ruukki.com
Uniaxial crusher simulates wear in
crushers and tippers while transport
• Crushing of gravel with high force up to 86 kN
• Fresh granite (4-6,3 mm) for each crush
• Typical test duration 1000 compressions
Sample
Abrasive cup
Supply tube
ruukki.com
Crushing pin-on-disc simulates wear
in crushers and unloading of tippers
•Abrasives as loose particles
• 500 g in a test
•Used force 200 N
•Pin diameter 36 mm
•Disc diameter 160 mm
•Test duration 30 minutes (240 crushes)
• Running-in of 20 minutes
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Steels and abrasives have many kind of
interactions
• Deformation:
– Ploughing
– Wedge formation
• Embedding of abrasives
• Indentations
• Fatigue due to
subsequent impacts
• Chip formation
• Cutting
The harder steels have clearer scratches
and less abrasive remnants
S355 500HB
S355 500HB
Hardening can enhance wear resistance
• Work hardening takes place in
impacts, but also in high-stress
abrasion
• The tendency of work hardening is
beneficial, unless it makes the top
layer brittle
400HB 650HB V.Ratia et al. Wear 301(2013)94-101
Depending on the contact, hardness may
have a different role
V. Ratia et al. Tribology Online 8(2013)152-161
Abrasive properties affect the wear
mechanism
• Abrasiveness, crushability, toughness, hardness etc.
• Size, size distribution and shape
Abraded with quartzite: Hardness 1200 HV,
crushability 74%, abrasiveness 1840g/t
Abraded with tonalite: Hardness 960 HV,
crushability 18%, abrasiveness 1460g/t
WANTED:
Wear resistant steels
• High hardness and strenght
• Good impact toughness and ductility
• Work hardening
• Adequate machinability, weldability etc.
• Decent producing costs
400HB 650HB 500HB
