In 2013 Metalurgia S.A., as a member of WireRodTRIP consortium, has received external founding from the National Centre for Research and Development for developing TRIP steel wire production methods.

TRIP steel (Transformation Induced Plasticity) are characterised by excellent formability, thus they are suitable for components of complicated shape, requiring high strength and good energy absorption. Perfect combination of high strength and formability of the TRIP steel is a result of phase transition of residual austenite to martensite during the forming process.

Nowadays, the TRIP steel, that belongs to the group of so called modern steel, more and more widely used in production of car bodies and elements of crush space of the car bodies. The reason is the TRIP steel combines the most desirable properties of car body sheet, i.e. high strength and high ductility.

Additionally, this type of steel is able to absorb energy not only due to change of shape (the crush space), but also due to change of the internal structure. It is an additional advantage, when human safety depends on the metal elements.

The innovation, on a global level, is using the TRIP steel to produce wire, and above all, elements made of wire. This innovative solution is an object of industrial research of Metalurgia S.A.

Metalurgia has tested and analysed the parameters of drawing wire of wire rod made of TRIP steel, focusing on its usability in production of bolts, screws, special wire - including stitch wire and spring wire.

What is TRIP steel

TRIP steel is a low-carbon steel, with basic components content specified below:
C     - 0,1 ÷ 0,25%.
Mn     - 0,4 ÷ 2,5%
Si     - 0,4 ÷ 1,8%
Therefore it is a common low-carbon steel, in which multiphase structure was obtained by applying appropriate steel cooling process after the rolling. To maintain the unique properties of the TRIP steel, thermal processing should not be applied. Among many steel grades used at present in the steel industry, the TRIP steel exhibits highest ductility in relation to strength.

Scope of research

Metalurgia S.A. has researched the properties of wires made of TRIP steel obtained on basis of following grades: S355JR, 27MnSi5, G4Si1. The diameters of wires ranged from : 2,0 to 7,5 mm , and the obtained strength ranged from 680 to 1600 MPa. It is worth remembering that TRIP wires may be produced also of another grade of low-carbon wire rod (the grade may be selected to match the individual needs of the customer), with the chemical composition fitting into the above specified ranges. In general, the minimal amount of wire rod, that may be ordered in a single order, with individually selected chemical composition, is the tap amount - approximately 120 tons.

Metalurgia S.A. carries out research in close cooperation with the Technical University of Częstochowa. The sample screws M15x12 made forcomparison purposes of low-carbon TRIP steel and C40 steel proved that the mechanical properties (Rm, R02) of the screws made of TRIP steel are higher than in screws made of medium-carbon steel.

Possible applications of TRIP steel wire

1. Bolts
- production of bolts with complicated shapes of thread and the screw itself (at present such production is possible using very ductile but low-strength steel),
- elimination of thermal processing - it is neither necessary nor possible to apply annealing in order to improve ductility - thus the production cost is reduced,
- the cost of wear and tear of tools is reduced due to better start parameters of ductility,
- improvement of strength parameters of bolts - possibility of using bolts of smaller diameter - the structure weight is reduced,
- improvement of strength parameters of bolts, therefore the thermal processing of  ready-made bolts may not be necessary (no hardening or tempering).

2. Screws
- production of screws with complicated shapes of thread or head,
- decreased probability of the blade tearing the material in case of high strength materials,
- thermal processing may be eliminated of the production process,
- the cost of wear and tear of tools is reduced due to better start parameters of ductility,
- improvement of strength parameters of screws.

3. Stitch wire
- better strength parameters are possible without using medium or high-carbon steel,
- increased ductility of the wire with the same strength.

4. Springs
- possible use of low-carbon wires in production of springs - in case of less "responsible" applications (significant decrease of production costs).

5. High-strength bent elements
- replacement of high-carbon steel with low-carbon steel,
- possibility of using smaller diameter of wire (reduction of weight),
- possibility of bending complicated elements,
- longer life of bending tools,
- reduction of bending forces (machines of lower parameters are used, energy consumption is lower, possibility of damaging the bent element is reduced).

Further research

Metalurgia, continuing the project, would like to test the advantages of the TRIP wire in production of specific elements at the facilities of permanent business partners.

Suggested action plan:

1. Selection of partners based on specific needs, willingness to develop the product, using modern and innovative solutions:
- commercial discussions, selection of potential partners,
- technology meetings, defining needs and possibilities (stating the grounds for using the new material).
2. Selection of product that will be tested and subject to comparison.
3. Joint tests of the product carried out after the free sample is delivered.
4. Validation of tests (technical, technological, quality and economic parameters).
5. Production of trial batch.

Metalurgia invites the partners to participation in a unique and innovative project. There are great possibilities in using the modern material in production of wire and wire elements, and the costs of tests on the final product are minimal.
Potential benefits following implementation of the tests results concern in particular the economic part of the business: costs reduction, new high quality products, increase in sales, but the benefits also include:
- strengthening of the competitive advantage and the company's image as an innovative enterprise,
- development of new products, taking into account effective resources management,
- increase of employees competences due to providing access to innovative solutions.