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Hardenable MnB steel – good forming properties and high strength for precision steel tubes

Precision steel tube made of MnB steel for stabilizers in automotive engineering

MnB steels made by thyssenkrupp are delivered with excellent forming properties and are used among other things for the production of precision steel tubes.

MnB steels are characterized by high strength and homogeneity of mechanical properties after quenching and termpering. The good strength properties are obtained by carbon and manganese and by a small boron content. Segregation-optimized MnB steels with even greater strength and enhanced ductility in the quenching and temping are being developed.

Apart from MnB alloyed steels in accordance with DIN EN ISO 683-2 (previously DIN EN 10083-3), our range of products includes the steel grades of the tubor® range - our application-optimized MnB steels for precision steel tubes.

Premium material for lightweight automotive manufacturing: tubor® – our application-optimized MnB steel for the production of precision steel tubes

Precision steel tubes made of MnB steels for piston rods in shock absorbers.
Precision steel tubes made of MnB steels for piston rods in shock absorbers.

Owing to their excellent forming behavior, steels of the tubor® range are very well suited for welded, cold-rolled or cold-drawn precision steel tubes. The material features a homogeneous and fine-grained microstructure with a low sulfur and phosphor content. Segregations in the microstructure are significantly reduced by means of special technical processes. Thanks to the combination of an optimized manufacturing process on the one hand and chemical analysis attuned to the end application on the other, the tubor® steel grades offer greater strength and a improved ductility after quenching and tempering.

Application examples of precision steel tubes made of MnB steels

In automotive manufacturing, precision steel tubes offer great potential for cost and weight reduction and are used among other things for stabilizers, piston rods in shock absorbers or driving shafts and camshafts.

thyssenkrupp supplies the steel grades as per the product information or the reference steel grades in accordance with the respective standards.

tubor® – special MnB steels for precision steel tubes

Steel grade designation Standard designation1 THICKNESS2
from _ to in mm
WIDTH2
max. mm
tubor® 26 26MnB5 1.95 – 13.00 2,030
tubor® 34 34MnB5 1.75 – 18.00 1,630
1. According to DIN EN ISO 683-2 (previously DIN EN 10083-3). | 2. Not all thickness and width combinations possible. |

Chemical composition

Steel grade ­ C [%] ­
Si [%]
max.
Mn [%] ­ P [%]
max.
S [%]
max.
Al [%] ­ Cr [%] ­ Ti [%] ­ B [ppm] ­
tubor® 26 0.23 – 0.27 0.15 – 0.35 1.15 – 1.40 0.020 0.006 0.015 – 0.055 0.05 – 0.20 0.015 – 0.045 15 – 40
tubor® 34 0.33 – 0.37 0.15 – 0.35 1.15 – 1.40 0.020 0.006 0.015 – 0.055 0.05 – 0.20 0.020 – 0.050 15 – 40
Mass fractions in ladle analysis.

MnB steel according to DIN EN ISO 683-2 (previously DIN EN 10083-3)

Steel grade designation Reference grade Material no. THICKNESS1
from _ to in mm
WIDTH1
from _ to in mm
20MnB5 20MnB5 1.5530 2.00 – 13.00 70 – 1,630
30MnB5 30MnB5 1.5531 2.00 – 13.00 70 – 1,630
39MnB5 389MnB5 1.5532 2.00 – 13.00 70 – 1,630
27MnCrB5-2 27MnCrB5-2 1.7182 2.00 – 13.00 70 – 1,630
33MnCrB5-2 33MnCrB5-2 1.7185 2.00 – 13.00 70 – 1,630
39MnCrB6-2 39MnCrB6-2 1.7189 2.00 – 13.00 70 – 1,630
1. Not all thickness and width combinations possible.

Chemical composition

Steel grade C [%]
Si [%]
max.
Mn [%]
P [%]
max.
S [%]
max.
Cr [%]
Mo [%] ­max. / - B [ppm]
20MnB5 0.17 – 0.23 0.40 1.10 – 1.40 0.025 0.010 0.10 8 – 50
30MnB5 0.27 – 0.33 0.40 1.10 – 1.45 0.025 0.010 - 0.10 8 – 50
39MnB5 0.36 – 0.42 0.40 1.15 – 1.45 0.025 0.010 - 0.10 8 – 50
27MnCrB5-2 0.24 – 0.30 0.40 1.10 – 1.40 0.025 0.010 0.30 – 0.60 0.10 8 – 50
33MnCrB5-2 0.30 – 0.36 0.40 1.20 – 1.50 0.025 0.010 0.30 – 0.60 0.10 8 – 50
39MnCrB6-2 0.36 – 0.42 0.40 1.40 – 1.70 0.025 0.010 0.30 – 0.60 0.10 8 – 50
Mass fractions in ladle analysis.

tubor® steels in use: Perfection through precision

Perfection through precision: tubes from Vincenz Wiederholt play a particularly important role for safety-related parts in vehicles.
Perfection through precision: tubes from Vincenz Wiederholt play a particularly important role for safety-related parts in vehicles.

Vincenz Wiederholt is a German company with a tradition stretching back over many years. It manufactures precision steel tubes that can be found in almost every European car, and are also key components for general engineering and the agricultural industry. Most of the input stock for the high-end precision steel tubes is supplied by thyssenkrupp Steel.

The premises for precision tube manufacturing at Vincenz Wiederholt are certainly impressive to behold: at the company's headquarters in Holzwickede, silver tubes are neatly stacked and waiting to be shipped to customers. The tubes shimmer and reflect the sun's rays almost like a vast kaleidoscope, depending on how the light strikes them.

The company processes more than 70,000 metric tons of steel annually, providing a versatile range of structural elements to industrial customers predominantly in the automotive industry. Around 80 percent of the products are used in the form of tubes, sections and components in automotive systems. These include, for example, shock absorbers, cylinder tubes, tubes for tanks or even camshafts. The manufacturing process is far more complex than the layperson might think.

Almost all of our products are used as safety-related parts in the automotive industry. This means we place the very highest demands on the material.

Uwe Seiger, Purchasing Manager at Vincenz Wiederholt

Quality combined with responsibility

During production, many parameters have to be coordinated with one another. At Vincenz Wiederholt, the manufacturing process from steel to the finished tube takes place in stages. Hardenable MnB steels from thyssenkrupp Steel serve as one of the basic materials. They are characterized by high strength, as well as homogeneity of mechanical properties after quenching and tempering.

Optimized production combined with analysis tailored to the ultimate application mean that our MnB steels in the tubor® series offer higher strength and improved toughness after quenching and tempering than other grades do. Their excellent forming properties in the as-delivered condition make them eminently suitable for welded, cold-rolled or cold-drawn precision steel tubes.

Hasan Bagci, Key Account Manager at thyssenkrupp Steel
Successful partnership of equals (from l.): thyssenkrupp Steel Key Account Manager Hasan Bagci together with Dr. Johannes Fien and Uwe Seiger from Vincenz Wiederholt.
Successful partnership of equals (from l.): thyssenkrupp Steel Key Account Manager Hasan Bagci together with Dr. Johannes Fien and Uwe Seiger from Vincenz Wiederholt.

Degree of purity of paramount importance

The hot-rolled wide strip supplied by thyssenkrupp Steel and cut into strips at service centers is welded into tubes at Vincenz Wiederholt. After annealing and chemical preparation, the tubular blank is threaded into a draw bench and then pulled through a die over a mandrel to reduce the outside diameter and wall thickness. The process optimizes the geometrical tolerance of the tube. The drawing process gives the inner surface of the finished tube particularly smooth surface properties. These are required, for example, for further processing into hydraulic cylinders for agricultural machinery. This is also ensured by the tubor® 26 and tubor® 34 steels supplied by thyssenkrupp Steel.

Only after completion can the tubes be checked for cleanliness and defects by eddy-current and ultrasonic testing. Any defects detected are costly, because all of the value added at Vincenz Wiederholt has already been incorporated into this tube.

Homogeneous and fine-grained

As a result, it is all the more important for the input stock from Duisburg to be of very high quality. Especially when the tube has to be annealed, the degree of purity of the steel is very important due to the underlying chemical analysis. "Manganese-boron steels are prone to an effect called segregation.

Manganese-boron steels are prone to an effect called segregation. This is not critical as long as it is located centrally in the wall of the strip, but if off-center, for example due to a casting process that is not well controlled, it can have a highly negative effect on the properties of the finished tube. The material from thyssenkrupp Steel is characterized by a homogeneous and fine-grained microstructure with low sulfur and phosphorus content. We take special process engineering measures to significantly minimize segregations in the microstructure – which is a huge advantage for us.

Dr. Johannes Fien, Process Development and Application Consulting at Wiederholt

Hasan Bagci is pleased that the tubor® steels meet the complex requirements of one of the leading precision tube manufacturers.

Cooperation made in the Ruhr region

It's surprising to think that thyssenkrupp and Vincenz Wiederholt have been working together since 1919. What started back then with a delivery of band iron has blossomed into a cooperation between partners who trust one another, and one that positively influences many end-user industries. For example, thyssenkrupp itself: Vincenz Wiederholt also supplies precision tubes to the thyssenkrupp Automotive business unit – a material cycle that benefits everyone.

www.wiederholt.com

General inquiry

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Contact

thyssenkrupp Steel Europe AG

Kaiser-Wilhelm-Strasse 100

47166 Duisburg, Germany

+49 (0)203 52-0

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