N DT of Round Cross-section
Stainless Steel Tube and Bar Product
By Joseph Baldauff. Magnetic
Analysis Corporation, Field
Engineering Manager
Stainless steel i.s used primarily be·
cause of its corrosion protection
properties. In a lesser extent, it is
used because some materials have
advantageous high temperature
properties or non-magnetic char·
acteristics. With that said stainless
Small high speed Eddy Current
Rotary with Triple Centering Rolls
steel grades are found in a wide
variety of applications from high
traffic concrete reinforcement bar to
medical implantable devices to aer·
ospace applications and evervwhere
in between. It is now a ubiquitous
material used virtually evervwhere
one casts their eye. The petroleum
industry is making increased quality
demands on stainless coiled tubing
used for various control apps; the
most demanding one being offshore
drilling and well control.
Because of increased quality demands on both the bar and tube
Encircling Eddy Current Coil
makers, there is demand for high
speed, reliable testing of this prod·
uct at the point of manufacture.
The typical bar stock or tubing end
user should demand product free of
harmful defects to maximize their
productivity and minimize liability.
Common defects of stainless steel
products include cracks, laps, tears,
internal and external pin holes, etc;
all depending on the manufactured
product and grade of the material.
ASTM (American Society for Testing
and Materials) A·276 document
contains specifications and descrip·
tions of many commercially avail·
able stainless grades in bar form.
Other ASTM standards regarding
stainless bars are: ASTM-314, ASTM·
484 and ASTM·582. There are many
other specialty grades that are not
covered by these specifications.
The ment ioned ASTM material
specificati ons do not cover any
known NOT methods for testing
steel bars. Bars are generally tested
to Mll ·STO (Military Standard)·2 154.
ASTM E·2375 and AMS·ST0· 2154
are restatements of the same MIL·
ST0·2154 document. There are
no known formal Eddy Current re·
quirements for bar stock, but t here
is wide EC testing done where high
quality is required - Both encircling
coil and rotary prol>e testing.
Various European standards such
EN- 10222·3 Ni Steel Forgings,
EN-10269 Steels and Nl Alloys,
EN- 10272 Stainless Steel Bars for
Pressure Applications cover various
stainless tube and bar products in
a broad sense. Even though there
is not any specific NOT requirement
contained within these standards
to test bar product, generally when
high quality is required, it is tested
to EN· I 0308 Ultrasonic testing of
Steel Bars or other.
There are also well established test·
ing methods for proving product
quality and these are reflected in
ASTM 01.01 and ASTM 03.03 which
is generally steel tubes. Numerous
EN (European) standards such as
the EN· 10246 series describe t he
various test methods for the inspec·
tion of st eel tul>es as well.
Because of reliability demands on
pressure tubes, there are many
standards regarding manufacturing
and testing of stainless pressure
t ubes. General standards for al·
loy and steel pipe include ASTM
A· 999 and ASTM A·1016. These
refer to other less general testing
practices also codified by ASTM
and commonly followed such as
ASTM E273; Standard Practice for
Ultrasonic Testing of the Weld Zone
of Welded Pipe and Tubing, and
E-426; Practice for Eddy Current
Examination of Seamless and
Welded Tubular Product, Austenitic
and Stainless Steel. Another practice
includes E·309; Eddy Current Testing
of Tubing Using Magnetic Saturation.
The bending and other cold working
processes during fabrication adds
st ress to the tubes w hich therefore
causes permeability noise issues.
The use of saturation allows for
higher quality testing by reducing
the noise caused by permeability.
NOT varies in methods but some
overlapping capability is advanta·
geous. The fundamental methods
are Eddy Current and Ultrasonic.
These can be broken down into sub
categories:
1. Eddy Current
a. The Eddy Current method can
include an encircling coil to
find short discontinuities and
also simultaneously look for
gross grade mixes.
b. The second EC method in·
eludes a rotary prol>e that may
l>e used to detect longitudi·
nally oriented surface defects
such as seams and laps in rods
and bars.
Both eddy current methods are used
for the detection of surface and subsurface defects. For internal defects
and other discontinuities/ an ultrasonic rotary may be applied.
High Speed Stainless final inspection Tube test line with triple drive rolls.
No hand operated bench mechanical adjustments, all done by entering tube diameter.
method. This method can find near
sub surface condit ions and surface
seams.
In relatively coarsely finished product. sur·
face seams can be detected with UT method
when the end user prefers coarsely finished
raw material for economic reasons includ·
ing the fact t hat a hot forging process works
best with hot mill finished material. The UT
rotary method allows the hot mill to supply
pre-screened high quality product to this
customer.
The modern NOT Devices now can meet
these needs at production speeds.
The very low production rate, spin t he bar/
tube systems are now used primarily for
requirements to the B, A or AA test levels can
now be met at a high test speed wit h a mod·
ern multi-channel rotary equipment
Mechanical setup can now be as simple as
an entry on a screen to show the product
diameter and the change of a few guide
bushings. The mechanical settings are now
greatly simplified.
I
Transducer arrays allow high inspection rates
without compromising test reliability.
These meet the demanding standards of var·
ious high quality product consumers. Indeed
t hese systems are the only option in many
cases w here extreme high quality/high prod·
uct volume is demanded.
incoming inspection and sometimes only
a fraction of product can be sample tested
when extreme quality requirements must
be met With a high speed rotary method,
the product can be test ed at high conveyor
velocities with high reliability and with low
test standard recheck cycles. High quality bar
Wit h all three methods mentioned, speeds
up to 400 It/min w hile achieving 100 per
cent volumetric testing are now possible.
Images provided by Magnetic Analysis
Corpora6on
2. Ultrasonics
a. Ultrasonic rotaries using a lon·
gitudinal wave can be used to
find internal and center voids
or even to find center line seg·
regation if quality demands are
high.
b. A second method that can be
used simultaneously in ultra·
sonic testing is a shear wave
..JI:liJIJ
Eddy Current coil ond Ultrasonic Rotary shown with o Constant Center Triple Drive Roll Bench
About Joseph Baldauff
Field Engineering Manager
1973· to Present: Magnetic Analysis Corporation
Qualifications: ASNT NOT LevellII Eddy
Current & Ultrasonic
17•
.,,
Degree: Bachelors of Science in Electrical
170
Engineering from University of Pittsburgh
P<
1971-1973
United States Navy
1967·1971
College- Electrical Engineering Technician
Ultrasonic Screen Shot showing the simple setup screen of an Echomac® FD5 Ultrasonic Electronics
April20J3
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Stainless Steel World Americas . April 2013
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