Giorgio Di Betta, sales director of Eural Gnutti, presents the new alloy, just registered by the Brescia-based company, which opens up great prospects for new uses in the mechanical segment of aluminium alloys for machining on high speed automatic lathes, having all what it takes to replace brass and steel bar
by Mario Conserva
Eural Gnutti is one of the major Italian aluminium extrusion companies, specialized and world leader in the
segment of bars for machining in alloys with high free cutting properties; its products have applications all over the world, especially in the mechanical and automotive segments. The company has invested and still invests continuously in the research and development of materials, technologies, plants and metallurgical and production cycles, from the chemical compositions of alloys to casting techniques, up to the heat and mechanical treatments of semis processed according to the final use. This is shown by the excellent results obtained during the last three years with absolutely innovative initiatives in terms of materials, first of all with alloy 6026 LF, (presented in A&L No. 3-2016, in the article on page 34), a medium strength alloy with the addition of small quantities of bismuth, suitable for high-speed machining on automatic lathes, designed and developed to meet the most recent environmental standards by eliminating lead. As we well know, lead is used to obtain small chips, but it is toxic and recent studies commissioned by the European Chemical Agency compared its risks and negative effects to those of hexavalent chromium and mercury.
The next step refers to 2033 LF, (see the article on page 20 in A&L n° 1-2019), a lead-free alloy like the previous one, but with medium-high mechanical properties and a very high level of chip forming performance, therefore intended to compete with other materials for machining on a wider range of applications.
We met Giorgio Di Betta, sales director of Eural, and before the preview of the latest new alloy launched by the Rovato-based company, specific for bars for machining with superior tensile properties, we asked him to comment briefly on the significant success of the first two alloys already on the market.
“I would like to start with a very brief introduction, Eural’s path in aluminium alloys for machining is a success story based on knowl-edge, metallurgical experience and commitment to research and development to focus the company on increasingly technological products intended to become the new market standards. The entrepreneurial philosophy of the company consists in focusing on a niche offer which implies quality, high added value products, and skills available to users. Launching original aluminium materials, able to open up the market to new products for new applications, is not just a new formula for alloying agents and additional elements in the chemical composition of the alloy, but it is the result of an overall revision of production paradigms, from foundry to extrusion, to heat and thermo-mechanical treatments developed for the specific type of semis in that material”.
Let’s summarize the logic of your metallurgical path starting from classic
Al-Mg-Si alloys up to copper alloys, starting in chronological order with alloy 6026 LF (Lead Free).
“This is a lead-free 6000 alloy, which also does not contain tin, an element which has been widely shown to cause brittleness and breakage when parts made from alloys containing it are subjected to a strong stress and high temperatures. A particular additional element, which influences machinability, is bismuth, ranging between 0.5 and 1.5% by weight. The alloy, due to the absence of lead, is therefore compliant with Directives 2000/53/CE (ELV) and 2018/740/EU (RoHS II), the latter requiring a lead content equal to or less than 0.1% starting from 18/5/2021; in terms of general properties, 6026 LF has good corrosion resistance, medium-high mechanical strength, good attitude to decorative anode oxidation and hard oxidation for industrial use. Also used in hot forging, it is suitable for applications in the mechanical, automotive, electro-technical and electronic sectors, and is used for the manufacture of nuts, screws, bolts, threaded rods, small parts, replacing and improving upon aluminium alloys of the 2000, 6000 and 7000 series, as well as, to mention just the most famous alloys, 2007, 2011, 2030, 6012, 6020, 6061, 6065, 6082, 6262, 6064A, 6262A, 6351, 7020”.
The next step led you to the Al-Cu series, but still on medium and medium-high levels of mechanical properties, also considering their capability of undergoing surface treatments and the possibility of being welded, compared to the classic 2011 alloy.
“Let’s talk about our new 2033 LF alloy, which also does not contain either lead or tin, so it fully complies with recent restrictions on the use of alloying agents which may constitute health hazards, such as the previously mentioned 2018/740/EU RoHS II.
The 2033 LF alloy obtained an immediate success compared to alloys such as 2011, 2007, 2030 in different application sectors (automotive, electrical and electronic, defence, moulding, screws, bolts, nuts, threaded parts even with limited thicknesses), for machining on high speed automatic lathes due to many positive factors: excellent machinability with any type of tool, excellent chip forming performance (thin chip), longer tool life; high mechanical characteristics with a guaranteed minimum level of ultimate tensile strength of 370 MPa, which allows, compared to the 2011 alloy which is its most natural reference point, a higher tool feed rate, therefore time / cycle optimization and productivity improvement up to 15%, with the further advantage of a better capability of being anodized and welded”.
This brings us to the upper bracket of hard alloys with very high mechanical strength and properties difficult to associate with machinability. So far, light alloys found many difficulties in this type of use. How did you obtain this new material, developed in your research laboratories, thoroughly tested and now ready to enter the market also as an alternative to brass and steel bars?
“The typical hard aluminium alloys are the quaternary alloys of the 7000 series (Al-Zn-Mg-Cu), such as 7075, with high mechanical strength values, ultimate tensile strength greater than 450 MPa, but difficult to extrude, hardly suitable for mechanical machining, critical with regards to toughness and fracture, corrosion and stress corrosion cracking, heat treatment and temperature sealing. We set ourselves the objective of a machinable material capable of ensuring ultimate tensile strength values of not less than 490 MPa, suitable for hot forging and
less critical in all the other mechanical and technological properties with respect to the 7000 alloys; finally, suitable to be treated with the production processes already developed for 6026 LF and 2033 LF, specific for alloys for machining. We focused our attention on alloy 2014A in terms of mechanical properties, with a target of 490 MPa as guaranteed minimum ultimate tensile strength. The development considered the use of bismuth and the specific details of the entire production cycle already fine-tuned with the previous alloys in order to obtain tailor-made micro-structures with the advantage of good chip forming performance, remarkable hardness, plastic transformability, tenacity and better corrosion resistance and weldability compared to Al-Zn-Mg-Cu alloys.
Having naturally also considered as a reference point the excellent experience of our 2033 LF alloy, we obtained the new 2077 Lead Free aluminium alloy, just registered past February 19, 2020. We perfected its exclusive production cycle, from foundry to extrusion, heat and mechanical treatments, right up to bars; we tested its mechanical and machining properties, resistance in corrosive environments, weldability, surface treatment: we are certain that we made available to the market a new aluminium material with excellent properties compared to the initial objectives, also able to effectively replace brass and steel bars”.
Could you tell us something more about the chemical composition and properties of the new alloy? It is not difficult to understand that the copper content is rather high and that, as is the case with alloy 2014, the combined role of magnesium and silicon is very important.
“As I mentioned before the alloy has been just registered to the Aluminum Association, you will will be the first to receive the full identikit of the alloy and its properties. I would like to add that in the field of hot forging and free machining, there are aluminium alloys alternative to the traditional brass bar on the market, acknowledged as more convenient from many metallurgical, technological and application standpoints, but until now they were penalized by the need to perform additional heat treatments compared to standard cycles. Now there is our new 2077 Lead Free alloy and I underline a technical point of extreme interest for future users of the alloy: the material may also be used in its T4 temper, therefore with a simple natural ageing of a few days which already stabilizes at a very good level the degree of hardening of the material. It is clear that the classic T6 state with artificial ageing achieves greater resistance, however the option of a simple ageing at room temperature after a very simple quick quenching in water from hot working temperatures, is a great opportunity for users to simplify the times and costs of the production cycle, making it very similar to the cycle used for brass bars. We carried out numerous cycles of industrial-scale tests regarding this aspect and the results are truly of great interest. It is hardly necessary to add that the technical specifications of the new alloy will indicate in full detail the properties, procedures and treatments for the envisaged final use properties”.
We are therefore looking forward to the official presentation of this new aluminium material, which I believe has excellent opportunities to advantageously replace many hard and very hard alloys of the previous generation, such as 2014, 2014A, 2024, 7020, 7075 alloys, and which also has the ambition to establish itself as an alternative to brass and steel bars, generating unpredictable market developments. We may take pride in the excellent technical results of an extrusion company which, in a long term perspective, is among the very few, together with large integrated groups, to carry out research on basic metallurgy, to seek the added value of innovation and to gather its benefits for a real market growth.