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Special steel

The special steel business division is one of our mainstays with its tool steel products forming the basis for all other world-wide services. The expertise we have gained across the company’s history as well as our ability to adapt to new situations form the basis upon which our success has firmly rested to this very day. 


Tools steels for hot stamping of automotive components:

The history of hot stamping started in 1977 with a Swedish patent describing a process for hot sheet metal forming and quenching. Due to the fast cooling inside the forming tool the sheet metal achieves a very high tensile strength of 1000 to 2000 N/mm², depending on the sheet metal grade. At the turn of the millenium hot stamping became more and more popular. In 2015 more than 300 million automotive components have been produced by hot stamping, yet the market of hot stamping parts is still growing. In contrast to cold stamping, hot stamping leads to a heat up of the tool surface, said heat needs to be removed quickly - otherwise there is a risk of reducing wear resistance of the tool. In the past, hot stamping tools were often made of standard hot work tool steels such as 1.2367 (X38CrMoV5-3) or 1.2344 (H13, X40CrMoV5-1) - transfering well established experiences from die forging, die casting, or hot extrusion applications. However, new material concepts are required that can lead to higher tool service lives.  Due thanks to  to the close cooperation with customers, research institutes and universities, Dörrenberg Edelstahl has developed new special steels for hot stamping that show superior properties compared to standard hot work tool steels. Special steel WP7V is a well known material that is widely used by several hot stampers. WP7V´s excellent balance of wear resistance and toughness results insignificantly improved tool life, less maintenace work, and higher process safety. Special steel CP2M® is a new development that has a high wear resistance and a high thermal conductivity. Due to these combined properties, the customers benefit from an improved tool life and a faster production, resulting in higher productivity of the hot stamping process. Additional information can be found in our technical data sheets: 1.2367, 1.2344, WP7V and CP2M®. 

Conferences:

· 71. HärtereiKongress, HK 2015, 28.-30. Oktober 2015, Köln (DE): "Optimierte Eigenschaften von Werkzeugstahl für Presshärtewerkzeuge"

· 3rd ICSCM, 02.-03. November 2015, Bochum (DE): "Tool steels for hot stamping of high strength automotive body parts"

· 10th International Tooling Conference, Tool 2016, 04.-07. Oktober 2016, Bratislava (SK): "Thermal Conductivity of Quenchable Martensitic Steels"

· Metal Forming Technology Day, MEFTECH 2017, 12. Mai 2017, Bursa (TR): "New Developments in Tool Steels for Hot and Cold Stamping of Sheet Metals"

· 11th China Automotive Lightweight Technology Symposium, ALTS 2017, 4.-6. September 2017, Changsha (CN): "Super Long Life Automobile Hot Stamping Tool Steel and its Application Case Analysis"

· NAFTA - Training Center for Hor Stamping Technology - 6th PHS Suppliers Forum, 28.-29. September 2017, Caryville (TN, USA): "Tool Steel Solutions for Hot Stamping Dies"

· 12. Erlanger Workshop Warmblechumformung, 23. November 2017, Fürth (DE): "Herausforderungen bei Werkzeugstählen für die Warmumformung von Strukturbauteilen"

 


Special steel for extruder screws

In the plastics industry, extruders are considered to be vital for the production of thermoplastic materials. During the extrusion process, granules made of plastics or other hardenable materials are homogenised in an extruder, also referred to as screw extruder, and extruded through a shaping nozzle. The core element of an extruder is the screw, which must resist high loads due to abrasion, adhesion and corrosion. The wear resistance capacities of a screw are determined and affected by the alloy constituents, structure conditions, heat hardening and antifriction properties of the steel used. For specific materials, special wear protection or hard-facing layers are additionally required.

Dörrenberg is a leading specialist, particularly in this field: The company produces high-quality bar steel for manufacturing extrusion screws and is a supplier for national and international leading-edge companies in the field of screw production with high-quality products that meet the highest requirements and challenges. In addition to nitriding steels (1.8519, 1.8550), these also include tool steels (1.2379, 1.2343, 1.3343), corrosion-free steels (1.4112, 1.4122) and special materials such as type RN15X®, as well as CPR and PM materials.

To this end, Dörrenberg features extensive warehouse stocks and appropriate availability of materials, also with regard to special materials, ensuring world-wide just-in-time delivery of ready-made materials. The combination of technical know-how and stock supply specifically targeted to customer demands has allowed Dörrenberg Edelstahl to become a leading partner of the extrusion industry over the last few years.


PRESSURE CONTROLLED ARGON FLUSHING

With the use of pressure controlled Argon, Dörrenberg Edelstahl implements an efficient process for preventing unwanted reactions during steel melting. An inert Argon flush gas is used during the mixing of molten steel to aid the homogenisation of temperature and composition.

At Dörrenberg Edelstahl, Argon gas is used for DETEM vacuum treatment, among others, which is a specially developed process for vacuum degassing small batches. Argon ensures optimal degassing of the molten steel by constant flushing. For materials with strict purity requirements, a special flushing process referred to as purity degree flushing is used. The result is that non-metallic inclusions are carried to the slag by the Argon. The parts are transported to the slag by argon, which is introduced into the molten steel through a flush block in the bottom of the furnace ladle.

For the flushing process, the flushing duration is one of the decisive factors, bearing in mind that a longer duration is not always better. Another factor, referred to as flush-up behaviour, is of equal importance. The surface of the flush block, through which argon is introduced into the molten metal, is only slowly freed from the metal at the beginning of the flushing process. The problem is: the dosage of the required argon quantity. If argon is introduced manually, the flushing effect can only be seen at the surface of the slag; however, in many cases the effect then shows up abruptly and excessively. If this happens, a large amount of slag is drawn to the bottom, which in turn results in the accumulation of unwanted particles instead of the intended separation.

Dörrenberg solves this problem by using pressure-controlled argon flushing, which represents the most efficient technology that is currently on the market. It prevents the introduction of slag particles. For this process, the optimum flow quantity of the gas is determined in noncritical tests, adjusted appropriately, and kept at a constant level using a Siematic control unit. In this way, the control unit increases the pressure instead of the quantity of the gas. The decisive advantage of the system is that it provides information about duration and quantities during the entire vacuum treatment. 

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