Seamless tubes are not only our passion; they are also part of our foundation: Since the Mannesmann brothers invented the seamless tube in 1885, we have continuously developed and enhanced the seamless tube production process. We work closely with tube manufacturers and partners, who serve the OCTG, construction, and automotive industries, to ensure that our technology and solutions meet the demands of the tube and pipe market.
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Advanced mandrel mill technology
The continuous rolling process – using mandrel mills – has been successfully used as a method of producing seamless steel tubes since the 1970s. The mandrel mill comprises several two-roll stands, which roll the hollow longitudinally to form a shell. SMS PQF® (Premium Quality Finishing) plants allow for operation at maximum efficiency, optimized operational costs, and reduced downtimes without compromising on productivity and high-quality results; while conventional seamless tube lines cannot viably compete with the high-precision PQF® quality, nor with its levels of productivity.
A PQF® mill consists of up to six stands, with three driven rolls each. The force is therefore applied more uniformly across the circumference of the rolls than it is with MPM (Multistand Pipe Mills) technology featuring a conventional two-roll arrangement.
Whether high-alloy steel tubes or particularly thin-walled precision tubes, our PQF® technology is designed to produce even the highest-grade products efficiently and reliably. By using less material, it achieves better output than conventional solutions. This ensures savings in tool and energy costs thanks to low reheating during the rolling process and thus a smaller CO2 footprint.
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PQF Mill in Changbao’s Seamless Tube Plant by SMS group in China -
Push bench mill (CPE/TPE)
CPE (Cross-roll Piercing and Elongation) and TPE (Three-roll Piercing and Elongation) push bench process
SMS group has further developed the push bench process into CPE (Cross-roll Piercing and Elongation) and TPE (Three-roll Piercing and Elongation). This means thee product range is has thereby been extended compared to previous concepts and the processes offer substantial benefits in terms of both quality and cost efficiency. Both methods differ from the conventional push bench method in the first forming stage, the piercing process.
With the CPE method, the piercing press, elongator, and hollow billet reducing mill are replaced by a high-performance two2-roll piercing mill, which acts as a piercing and pre-stretching unit. The process therefore requires fewer forming stages, so plant owners can reduce conversion costs measurably. At the same time, they can use higher billet weights and achieve better wall thickness tolerances. The output on CPE mills is considerably higher than with the conventional push bench method. Modern CPE mills, therefore, are a highly efficient, flexible, and economic alternative in the production of tubes with medium to small diameters.
With TPE mills, SMS group uses a three3-roll instead of a two2-roll cross-roll piercer. As a result, the quality of the hollow before the stretching process on the push bench has increased even further.
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Assel mill
for the production of seamless heavy-duty tubes
The assel mill is a three-roll cross-rolling mill used for producing medium and thick-walled tubes of high quality and dimensional accuracy. They are mainly used for ball bearing tubes and general mechanical engineering pipes and tubes, which need to be subsequently machined. SMS group has continuously further developed this technology and thereby managed to double the maximum producible tube diameter. Today, tubes with an outside diameter of up to 460 mm and wall thicknesses of up to 80 mm can be produced on assel mills.
As part of the rolling process, a mandrel bar is inserted into the hollow – with the conventional assel process it is free-running, and with high-performance assel mills it is moved in a controlled manner. SMS group has further developed this proven technology for such high-performance assel mills, meaning the technology has been improved and the dimensional range extended.
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Assel Mill for the production of seamless heavy-duty tubes by SMS group -
Hot pilger mill
For the production of seamless tubes up to 28 inches
The hot pilger rolling method is one of the oldest processes for elongating pierced billets into tube shells. Today, it is mainly tubes for the power generation, petrochemical, and construction industries that are produced on hot pilger mills. A key feature of SMS group’s hot pilger mills is the large dimensional range of rollable stock – even for high-alloy steel grades.
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Rotary expanding mill
For the largest-diameter tubes
SMS group rotary expanding mills are used for producing seamless tubes with very large diameters, which cannot be produced on a ‘normal’ seamless tube plant. The tubes are first heated then rolled to larger dimensions – using this technology plant owners can produce a wide spectrum of finished tube diameters and wall thicknesses from just a narrow range of primary products.
The rotary expander is a special kind of cross-rolling mill with conical, axially adjustable rolls. The tubes are expanded by rolling them over a plug. The position of the rolls mandrel here determines the wall thickness of the tubes. This can also be adjusted hydraulically during the rolling process.
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Rotary expanding mill for the production of seamless tubes with the largest diameters
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Piercing mill
Quality right from the start
The piercing process is at the top of the process chain, which starts with the solid steel billet and ends with the seamless tube. It is of crucial importance for the subsequent quality of the finished tube, as the billet must demonstrate excellent surface and tolerance characteristics straight after piercing. Only then is it possible to produce high-quality tubes with flawless surfaces and high dimensional accuracy. The high-performance cross-rolling mills from SMS group are perfectly designed to achieve this, enabling particularly cost-effective production at the same time.
Cross-roll piercing ranks as the leading piercing method for seamless tubes and offers considerable advantages compared to alternative methods such as piercing presses or press-piercing mills. Plant owners are able to process heavier billets as well as achieve measurably closer wall thickness tolerances.
As an alternative to the two-roll piercing mill, three-roll piercing mills are also used for the piercing process. This further improves the wall thickness quality of the hollow.
SMS group has continuously further developed the cross-roll piercing process with several inventions, such as hydraulic gap control. Today’s high-performance cone-type piercers produce particularly thin-walled hollow blooms with very tight tolerances and the highest levels of productivity. These innovations give advantages during the subsequent processing stages in the production of seamless tubes: the loads on the elongating and sizing units are reduced and the production range can be increased. This enables tube manufacturers to produce more cost-effectively – even in the case of large dimensional ranges, small batch sizes, and low capacities.
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Billet centering machine
BCM for centered piercing
The Billet Centering Machine (BCM) ensures that the plug enters the billet exactly in the center to optimize the rolling process. For this purpose, the BCM makes recesses in one or both ends of the billets before the piercing process. As a result, the plug enters the billet precisely in the center.
Rolling solid billets over a piercer plug creates ‘hollows’. It’s crucial here that the piercing plug contacts the billets exactly in the center, otherwise faults known as ‘onion rings’ occur at the ends of the pipes. To avoid this, BCM makes recesses in one or both ends of the billets before the piercing process. As a result, the plug enters the billet precisely in the center, creating virtually no onion rings as it exits.
Moreover, the BCM ensures minimal wear on the plug and uniform wall thicknesses. Due to the optimized rolling process, the BCM also leads to increased productivity.
Benefits
- Optimized rolling process dues to the exactly centered entering of the piercing plug into the billet
- Optimized product quality through uniform wall thickness
- Increased productivity thanks to minimal wear on the plug
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Sizing and stretch-reducing mills
Quality right from the start
Sizing or stretch reducing is the last stage in the production of hot-rolled tube and plays a crucial role in terms of the variety and quality of the products. With solutions from SMS group, tube manufacturers benefit from a high degree of flexibility and reduced processing costs.
The diameter of the tube is reduced without an inside tool in the sizing mill and stretch-reducing mill (SRM). For this, it passes through a variety of three-roll stands. A smaller or larger number of stands is used depending on the diameter to be produced. During sizing, a low degree of longitudinal tension in the rolled stock is applied by using appropriate, fixed-speed reduction from stand to stand. With stretch reducing, on the other hand, the speed can be varied. Sizing and stretch-reducing mills can essentially be used independently of the process application.
By varying the stands and speed settings, plant owners can produce a broad spectrum of finished tube dimensions from just a few ingoing stock dimensions.
The high degree of flexibility offered by the process is used to minimize the machine and tool workload in the preliminary stage – the elongation process. Besides the roll speed, calibration of the rolls and their development from stand to stand play a crucial role in terms of the quality of the outer and inner surface of the stretch-reduced tube.
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Measuring system for rolls and passes
CaliView® measuring system
CaliView® is a system for inline measurement of the rolls and passes in seamless tube mills. It is a flexible solution for Premium Quality Finishing (PQF®), Multi Purpose Milling Machines (MPM), stretch-reducing mills (SRM), Precision Sizing Mill (PSM®), sizing mills, piercers, and tool shops.
CaliView® uses a camera to quickly and precisely measure the stands in a rolling mill so they can be aligned optimally. What sets the system apart is that it measures the rolls and passes to the pass line inline, making it possible to exactly assess the passes with the rolls installed in the mill for the first time. Here is how it works: A camera measures the alignment of the rolls – quick, simple, and in a contact-free way. According to a subsequent analysis of the measurement results, the rolls are aligned to optimize the pass to the pass line.
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Benefits
- Fast, precise, and contact-free inline measurement of all stands in the mill
- Visibility of the alignment of the rolls to the pass line
- Direct feedback via the mobile control device allows roll adjustment during measurement
- Identification of work-roll wear to ensure the maximum lifetime of the rolls
- Data-based system to draw up statistics enabling short maintenance times
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Roll dressing
KR groove dressing machine
The KR groove dressing machine for stretch-reducing mills, sizing mills, extracting mills, and push bench stands comes with a 3-axis continuous path control system combined with a higher-level measurement data computer. Those make it possible to produce any groove shape, whether round, oval, or round with parabolic side zones, enabling free groove design and forming process optimization. So, internal polygonization of tubes during the stretch-reducing process can be reduced or even completely prevented.
The machine is equipped with a measuring device, which detects the roll positions and the groove contours to be machined and transfers the data to a computer program. Next, the computer controls the rest of the machining process on the basis of these measured values. Following a defined sequence, the system machines the three rolls individually from the front of the stand. The cutter holders for each roll and the measuring sensor are mounted on a standard rotating turret with a rapid-release system. The cutter is made of ceramic or CBN material.
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Piercer plugs
PQSC® Premium Quality Surface Coating piercer plugs
During the first step of seamless tube production, we recommend the use of our PQSC® (Premium Quality Surface Coating) piercer plugs. Their special ceramic coating has a direct impact on your product quality as the plugs produce enhanced internal pipe surfaces. Especially durable, these plugs withstand extreme thermal and mechanical stresses. The ceramic coating features low thermal conductivity plus extreme hardness. It acts as a heat and wear protection shield and as a passive separating layer that significantly extends the service life of the piercer plugs, resulting in reduced tooling costs and increased productivity of your plant.
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PQSC® (Premium Quality Surface Coating) piercer plug -
Process control
CARTA® production planning and process control system
Computer-Aided Rolling Technology Application – Carta® for short – is a technological production planning and process control system to ensure optimal rolling mill operation.
With its proven rolling model and online measurement data, Carta® allows an in-depth insight of the rolling process and live optimization for each tube. Dedicated technological functions can be used to set specific quality features and affect the rolling process. Sophisticated tools enable subsequent evaluation, error analysis, and permanent optimization. In conclusion, Carta® provides three main benefits: increased yield, higher tube quality, and improved mill utilization.
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Process Control of SMS group Seamless Tube Plant at Changbao in China Benefits
- Process planning module takes care of mill settings and tool design
- Process management module controls the rolling process in real time, saving and analyzing the process data
- Process optimization module stores quality data and provides evaluations
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Premium finishing
Finishing solutions for premium quality
For premium threads of the highest international standards, such as API or GOST, we carry our TCG thread cutting machine and RMG coupling threading machine in our product range. Our machines provide high-quality finished products – nevertheless, regular checks are indispensable to ensure the proper quality of cut threads. Therefore, we offer an autonomous optical inline measurement system for examining threads and sealing lips on OCTG tubes. ThreadView offers the possibility to measure the negative flanks of premium threads and is the missing building block for the realization of a complete Digital Twin. The system not only enables a 100 % measurement of all produced threads; it also ensures an evaluation and documentation of the measurement data.
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Stacked thread pipes next to oil or gas platform -
Thread measuring system
ThreadView for OCTG tubes
Tubes are often processed on our thread-cutting machines (TCG) and used worldwide as oilfield tubulars (OCTG tubes). Our machines provide high-quality finished products to international standards, such as API or GOST. Also regulated by these standards are regular checks to ensure the proper quality of cut threads. That’s where ThreadView – a thread measurement system, which is fully integrated into the thread cutting line – comes into play.
ThreadView offers the possibility to measure the negative flanks of premium threads and is the missing building block for the realization of a complete Digital Twin. The system not only enables a 100 % measurement of all produced threads; it also ensures an evaluation and documentation of the measurement data.
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ThreadView autonomous measuring system for OCTG threads and sealing lips Benefits
- Risk reduction: Decrease the operational risk and the risk of a worst-case scenario in the oilfield thanks to 100 % measurement of all produced tubes
- Cost reduction: Decrease your operational costs thanks to automated measurement, evaluation, and documentation
- Reputation increase: Decrease the claim rate thanks to the direct feedback on quality results
- Digital ready: Be prepared for the market demand of tomorrow as ThreadView is the building block for your digital pipe twin
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