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This
equipment is for the ultrasonic inspection caster rolls following
a period of service but prior to machining them in a CNC lathe.
The ultrasonic inspection is carried out using a single fixed
Water Column Coupled Probe (WCCP) unit for the longitudinal shear
wave flaw detection in both directions.
Caster
roll sizes up to 800mm diameter and a maximum length of 3500mm
WCCP ultrasonic
probe units
Longitudinal
ultrasonic shear wave testing
Compression
wave testing if required
Can use
any CNC lathe with a FANUC controller
Fully automatic
determination of machining profile to remove defects from the
roll
Roll
inspection is necessary to ensure that rolls being returned to
the hot plate mill following reconditioning are free from surface
breaking and internal defects that may cause the failure of the
roll whilst in service. This page describes the use of our Automatic
Ultrasonic system for the inspection of Caster Rolls, and a scheme
which uses the data obtained to directly control the complete
renovation process.
The
ultrasonic inspection of the roll is carried out in a CNC lathe.
After the roll barrel has been skimmed, to remove the working
surface - which is a stainless steel cladding - to provide a suitable
surface for ultrasonic inspection. The ultrasonic probe assembly
fits into the CNC lathe tool turret, mounted in a standard machine
tool post, and uses the lathe cutting fluid as the ultrasonic
couplant. The probe assembly uses a gap scanning technique, where
he probes' faces are kept at a 0.3mm gap from the surface of the
roll; the fluid fills the gap to provide coupling of the ultrasound.
The
CNC lathe operator initiates the test by entering the roll diameter
and the barrel length into the system. This information will be
used by the system to generate a CNC program which would position
the ultrasonic probe assembly to maintain the 0.3mm gap and automatically
select an appropriate roll RPM to ensure that the peripheral speed
of the roll would be approximately 600mm/s.
A
single pass of the roll whilst it is rotating is required for
the ultrasonic inspection, this done by using the CNC lathe to
provide a 10mm pitch helical scan of the roll barrel, scanning
from the chuck end to the tailstock end . The computer section
of the system is used to record the defects found by the ultrasonic
system and calculate the depth and the position of each defect
relative to the reference, which is the tailstock end of the roll
barrel.
Based
on the position and depth of the defects found, the computer will
create a machining profile to completely remove the defects from
the roll barrel. In the creation of this machining profile, the
computer takes into account the requirement that each side of
any cut-out should have a 30 degree angle, to facilitate the welding
process. If two defects are less than 50mm apart then the land
between them is also machined away to the depth of the deepest
defect. This profile is presented to the machinist in the form
of a roll machining graphic. This shows the relative position
of each machining band each band being a circumferential cut of
6.5mm together with the volume of material to be removed and the
deepest depth of defect, and is also presented in the form of
a roll inspection report.
The
machinist responsible for the roll could then decide if the roll
has to be scrapped or reworked. If the decision is taken to rework
the roll, the computer system can be instructed to take the required
machining profile and convert it in to a program for the CNC lathe.
This lathe program can be downloaded to the lathe's controller,
and the program run.
Roll
Inspection Software
The
roll inspection software is designed to:
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Allow entry dimensions of the roll to be tested.
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Send
an inspection CNC program to the lathe to scan the lathe using
a threading cycle.
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Collect
and collate the data from the ultrasonic instrumentation, so
that a machining profile may be displayed.
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Post-process this machining profile to generate the CNC program
to remove the defects found.
FOR
MORE INFORMATION PLEASE SEE: EFFECTIVNESS
OF CLOSED LOOP DEFECT LOCATION AND REPAIR IN CASTER MILL ROLS
(pdf format) from our Technical Papers Library
To obtain this
information as an Adobe Acrobat document Click
Here.
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