If you are a user of Hollow Bar, our products are sure to interest you. We are setting new industry benchmarks in the production of Hollow Bars. ISMT produces Hollow Bars to the tightest tollerances & the highest quality standards in the industry. This means, as a customer you get more length (meters) and therefore more finished product per tonne of Hollow Bar that you purchase. This also means our Hollow Bars cost less to machine than our competitors.
At ISMT, we believe the only way to guarantee quality is to stand responsible for the entire production process. For that reason we start with producing all our steel in-house. We bring to bear over 20 years of experience in manufacturing high-grade Bearing Steel to all our manufacturing processes and to all our steel products (we are among a few select manufacturers globally to be approved by SKF and FAG for the supply of Bearing steels).
We produce our steel through the electric arc furnace route. The raw material mix is chosen and prepared carefully to ensure the highest standards of cleanliness. All heats are ladle refined and vacuum degassed before continuous casting and rolling. Right through the production process, we maintain full traceability of the material and a record of the tightly controlled process parameters. This ultra-clean steel forms the starting point for the manufacture of our tubes and hollow bars.
The manufacture of precision seamless tubes is as much a matter of equipment as it is of experience and process technology. We believe in investing in the finest of equipment. For making seamless tubes, we operate three Assel Mills, one PQF Mill, Pilger Mills and Cold Draw Benches. Our tube-mills are imported from Shloemann Mannesman in Germany and incorporate the best in technology. With regards to experience, our team is amongst the most technically qualified anywhere in the world the hollow bars that we produce for the mechanical industry reflects this experience.
ISMT Hollow Bars conform to European EN 10294-1 standards. The Clean Turned Size refers to the finished machined size that is guaranteed to be produced by chucking the Hollow Bar on the OD. Each Clean Turned Size, defined in steps of 5, 10 or 20 mm corresponds to a delivered hollow bar size. The difference in these two sizes represents the material that needs to be machined off.
ISMT offers the tightest tolerances in the industry. We are able to do so through stringent control of our process parameters and because of proprietary processes that we have developed. With over 25 years of experience in operating Assel Mills, we have a complete understanding of the primary parameters that are responsible for variations in product quality and we are able to control these parameters very carefully. Similarly, we have developed special surface treatment and cold sizing processes that allow us to ensure extremely good dimensional control as well as surface cleanliness.
In case of Hollow Bars, tighter tolerances translate directly into cost savings.
In order to guarantee a clean turned size, we are able to provide a finer machining allowance than our competitors. This not only means that you have less material to machine but also you get a greater number of finished components per tonne of hollow bars that you purchase.
With over 25 years of experience in the Mechanical Tubes business, we fully understand that machinability and weldability of our tubes is of the essence to our customers. Therefore, we have invested vast efforts in developing and perfecting the SpeedCut ™ grades of steel.
Our Hollow Bars are regularly put through testing procedures to benchmark machinability of the steel. The standard procedure used is to generate Taylor Curves for steel (as per ISO 3685 ? 1993) which provide a proxy measure of tool life as a function of the cutting speeds employed while machining the steel.
The graph below demonstrates the standard Taylor Curve for the SpeedCut ™ grade as compared to the requirements as per EN 10294-1 standard.
ISMT produces four standard grades of SpeedCut™ Hollow Bar: three micro-alloyed grades (470, 420, 590) and one regular grade (355). Although, the three micro-alloyed grades share the same chemistry they differ in their heat treatments.
|470, 420, 590||< 0.22||< 1.70||< 0.5||< 0.025||0.020 - 0.035||0.020 - 0.035||0.08 - 0.15|
|355||< 0.22||< 1.60||< 0.55||< 0.030||0.015 - 0.050|
The Mechanical properties of EN-10294-1:2005 (E)
|Steel Grade||Upper yield strength ReH min
Mpa For TN in mm
|Tensile strength Rm min Mpa
For TN in mm
A min %
absorbed energy KV,
in, J at a test
temperature of - 20º c
|Name||Number||TN<=16||16< TN<=25||25< TN<=40||40< TN<=50||TN< =16||16< TN<=25||25< TN<=40||40< TN<=50|
* At the discretion of the manufacturer the elongation may also be determined in the transverse direction.
In this case the minimum values to be achieved to be achieved shall be those for the longidinal direction minus 2 points
We assure a Ceq of less than 0.57 and thereby guarantee weldability. Nevertheless , as a practice, we recommend the following :
For tubes of thickness > 16 mm: Pre-heating between 200 ° and 250 ° C
For tubes of thickness < 16 mm: Pre-heating between 100 ° and 120 ° C
Stress Relieving at 600 ° ° C
Approximate transformation temperatures are as follows :
|Transformation Temp||SPEEDCUT 420, 470, 590||SPEEDCUT 355, 355J2|
|Acl||720 °c||715 °c|
|Ac3||815 °c||810 °c|
|Austenitisation||880 °c||880 °c|
We also delivery Hollow Bars in quench & tempered conditions, customized to specific needs.
The following tables show the finished machined sizes (guaranteed clean turned size with OD chucking), the delivered sizes (OD, Wall Thickness), weight per meter, and the guaranteed clean turned size if chucked on the ID.