EP3194632B1 - Cast-iron alloy, and corresponding part and production method - Google Patents

Description

The present invention relates to a cast iron alloy.

Known tools are known in the state of the art to manufacture parts made of composite material carbon fibers and resin or thermoplastic material. These carbon / resin composite parts are molded at a temperature usually up to 250 ° C.

The tools must have a low coefficient of thermal expansion, or a coefficient of thermal expansion close to that of the material or the material to be molded in the temperature range used for forming.

For forming temperatures above 250 ° C, there are tools manufactured only in mechanically welded.

For forming temperatures up to 250 ° C with foundry tools, there are a number of alloys with an acceptable coefficient of thermal expansion, which is not the case for higher temperatures.

In particular, certain thermoplastic materials (polyimides for example) and composites containing these same thermoplastics require higher temperatures. Increasing the forming temperature also allows in some cases to decrease the duration of a production cycle.

Currently, there are foundry alloys for tools that maintain a stable coefficient of expansion up to 250 ° C. There are also sheets to maintain a stable coefficient of expansion up to 400 ° C. A Ceramvar cast iron alloy with spheroidal graphite or lamellar graphite is known comprising, in% by weight, the following elements: Carbon (C) between 0.05%, Silicon (Si) 0.30%, Nickel (Ni) between 28.5% and 29.5% , Cobalt (Co) between 19.5% and 20.5%, Manganese (Mn) 0.50%, and / or Phosphorus (P) 0.020, and / or Sulfur (S) 0.020. Steel tools used to manufacture parts made of composite material or of thermoplastic material are also known. These tools, however, have a relatively large wall thickness, since the steel is likely to have structural defects (sinkholes) when the tools are manufactured with a small thickness.

The object of the invention is to enable the manufacture by molding of a cast iron part whose thermal expansion is low for high temperatures and in particular up to 400 ° C., and whose expansion coefficient remains stable up to these temperatures. high temperatures.

In particular, the invention aims to design an alloy that allows the manufacture of a tool having a low coefficient of expansion and stable, including at high temperatures. Also, the invention aims to design an alloy that allows the manufacturing such a tool having a small wall thickness while certainly having few structural defects.

For this purpose, the subject of the invention is a spheroidal graphite or graphite graphite cast iron alloy consisting of, in% by weight, the following elements: Carbon (C) between 1.2% and 3.5%, silicon ( If) between 1.0% or 1.2% and 3%, Nickel (Ni) between 26% and 31%, Cobalt (Co) between 15% and 20%. Optionally the alloy comprises: Magnesium (Mg) between 0.02% and 0.10%, Manganese (Mn) ≤ 1.5%, Chromium (Cr) ≤ 0.5%, and / or Phosphorus (P) ≤ 0 , 12 or ≤ 0.04%, and / or Sulfur (S) ≤ 0.11 or ≤ 0.03%, and / or Molybdenum (Mo) ≤ 0.5%, and / or Copper (Cu) ≤ 0, 5%, the rest being Iron and unavoidable impurities.

• la teneur en Nickel (Ni) est au moins 27% ou 28% et/ou au plus 30% ;
• la teneur en Cobalt (Co) est au moins 16% et/ou au plus 18% ou 19% ;
• L'alliage comprend Carbone (C) au moins 1,4% ou 1,5% et au plus 3,1% ou 3,3%, et/ou Silicium (Si) au moins 1,4% ou 1,5% et au plus 2,6% ou 2,8% ;
• la teneur en Manganèse (Mn) est au moins 0,01% et/ou au plus 1,0% ;
• la teneur en Cuivre (Cu) est au plus 0,2%, 0,3%, ou 0,4% ;
• la teneur en Molybdène (Mo) est au plus 0,2%, 0,3%, ou 0,4% ;
• la teneur en Chrome (Cr) est au plus 0,3%, 0,4%, ou 0,5%.

According to particular embodiments, the alloy may comprise one or more of the following characteristics:

• the nickel (Ni) content is at least 27% or 28% and / or at most 30%;
• the Cobalt (Co) content is at least 16% and / or at most 18% or 19%;
• The alloy comprises Carbon (C) at least 1.4% or 1.5% and at most 3.1% or 3.3%, and / or Silicon (Si) at least 1.4% or 1.5% and not more than 2.6% or 2.8%;
• the Manganese content (Mn) is at least 0.01% and / or at most 1.0%;
• the copper (Cu) content is at most 0.2%, 0.3%, or 0.4%;
• the content of molybdenum (Mo) is at most 0.2%, 0.3%, or 0.4%;
• the chromium (Cr) content is at most 0.3%, 0.4%, or 0.5%.

The invention also relates to a part made of a cast iron alloy, as defined above, and in particular the part being a tool.

• Coulée de la pièce dans un moule,
• Une fois la pièce coulée dans le moule, faire subir un refroidissement à la pièce dans son moule, ce refroidissement étant notamment inférieur à 50°C/h.

The invention also relates to a method for manufacturing a part as defined above, characterized in that it comprises the following steps:

• Casting the piece in a mold,
• Once the piece has been poured into the mold, the part must be cooled in its mold, this cooling notably being less than 50 ° C./h.

The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the single FIGURE on which the thermal expansion behavior of three alloys is represented, by means of FIG. evolution of their coefficient of thermal expansion as a function of temperature.

The subject of the invention is a cast iron alloy. It allows to obtain parts whose coefficient of thermal expansion is weak and stable up to a temperature of 400 ° C.

The part is for example a tool, in particular a tool for manufacturing parts made of composite material or thermoplastic material.

All composition data are given in% by weight of the total weight of the alloy.

A first aspect of the invention is the chemical composition of the alloy.

The alloy is a cast iron alloy. The alloy may be a cast iron alloy with spheroidal graphite or lamellar graphite.

Its basic component is Iron (Fe). It also contains unavoidable impurities resulting from the elaboration.

The alloy comprises, in addition to Fe, carbon (C) between 1.2% and 3.5%, silicon (Si) between 1% and 3%, nickel (Ni) between 26% and 31%, and Cobalt (Co) between 15% and 20%.

In addition, the alloy may comprise magnesium (Mg) between 0.02% and 0.10%.

In addition, the alloy may comprise manganese (Mn) up to 1.5%, or up to 0.8%.

In addition, the alloy may comprise chromium (Cr) at a content between traces and 0.5%.

In addition, the alloy may comprise phosphorus (P) at a content between traces and 0.04% or between traces and 0.12%.

In addition, the alloy may comprise sulfur (S) at a content between traces and 0.03% or between traces and 0.11%.

In addition, the alloy may comprise molybdenum (Mo) at a content between traces and 0.5%.

In addition, the alloy may comprise copper (Cu) at a content between traces and 0.5%.

The nickel (Ni) content of the alloy may be preferably between at least 27% or 28% and at most 30%.

The cobalt (Co) content of the alloy may be preferably from at least 16% to at most 18% or 19%.

The carbon content (C) of the alloy may be preferably between at least 1.4% or 1.5% and at most 3.1% or 3.3%.

The silicon (Si) content of the alloy may be preferably from at least 1.4% or 1.5% to at most 2.6% or 2.8%.

The Manganese content (Mn) of the alloy may be preferably between at least 0.01% and / or at most 1.0%.

The copper (Cu) content of the alloy may be preferably less than 0.2%, 0.3%, or 0.4%.

The Molybdenum (Mo) content of the alloy may be preferably less than 0.2%, 0.3%, or 0.4%.

An iron-based alloy with a low coefficient of expansion is known as Fe-Ni36 (trade name INVAR®). It is a steel developed in the late 19th century. It contains 36% nickel and iron. The curve representing the expansion coefficient of iron / nickel alloys has an anomaly around 36% nickel: the coefficient of expansion is then much lower than for the other compositions. This is valid for low temperatures up to 130 ° C.

Various alloys were then developed from this base, in particular with cobalt as additive element. For example, the iron / nickel / cobalt alloy with 32% nickel and 5.5% cobalt has a lower coefficient of expansion than INVAR®, and above all, it keeps this property at higher temperatures.

In cast iron, there is the same anomaly as in steel, however the coefficient of expansion is a little higher. The Ni-Resist D5 (ASTM A439) at 35% nickel (iron rest) has in particular a low coefficient of expansion: 5 * 10 ^-6 K ^-1 .

Subsequently, as in steel, other alloys were developed, adding additions elements such as cobalt. Ferrynox N33 ® (33% nickel, 4% cobalt) gives a low coefficient of expansion and stability (4 * 10 ^-6 K ^-1 ) up to 180 ° C. Ferrynox N36 ® (36% nickel, 4% cobalt) has a higher coefficient of expansion (4.5 * 10 ^-6 K ^-1 ), but remains stable up to 250 ° C. The behavior of the coefficient of thermal expansion as a function of the temperature of the two FerrynoxN36 and FerrynoxN33 alloys is illustrated in the single figure.

According to examples, the alloy comprises, in addition to iron (Fe) and unavoidable impurities, only the following elements, within the limits indicated: VS Yes mn P S Cr Or MB Cu mg Co mini 1.2 1.2 footsteps footsteps footsteps footsteps 26 footsteps footsteps 0.02 15 Maxi 3.5 3 1.5 0.04 0.03 0.5 31 0.5 0.5 0.1 20 Example1 1.9 1.64 0.12 0.014 footsteps 0.03 29.44 footsteps 0,017 0.06 16.96 Example 2 1.9 1.63 0.12 0.014 0.006 0.03 29.06 0,002 0.02 0.04 17.49

This alloy is a spheroidal graphite cast iron.

The coefficient of thermal expansion of Example 1, indicated under the name Ferrynox N29K in the Figure, compared with thermal expansion coefficients of the two alloys of the state of the art (Ferrynox N33 and Ferrynox N36) is shown in the single FIG. .

The coefficient of thermal expansion of Example 1 is less than 6.4 * 10 ^-6 K ^-1 for a temperature below 400 ° C. Also, the coefficient of thermal expansion is relatively stable over a wide temperature range. It is between 6 * 10 ^-6 K ^-1 and 7 * 10 ^-6 K ^-1 over the entire range from 150 ° C to 400 ° C.
The mechanical characteristics of the sample are as follows: Resistance limit Re (MPa) Rm (MPa) rupture limit Elongation after rupture A% at 20 ° C 298 483 28.4 at 200 ° C 214 380 29.8 at 300 ° C 146 350 30 at 400 ° C 166 341 30.5 at 450 ° C 156 336 30.9

Another aspect of the alloy according to the invention is that it is weldable.

According to another embodiment, the alloy comprises, in addition to the iron (Fe) and the unavoidable impurities, only the following elements within the limits indicated: VS Yes mn P S Cr Or MB Cu Co mini 1.2 1 footsteps footsteps footsteps footsteps 26 footsteps footsteps 15 Maxi 3.5 3 1.5 0.12 0.11 0.5 31 0.5 0.5 20 Example 1.9 1.7 0.45 0.04 0.07 0.03 28.96 0,002 0.02 17.54

In this case, the alloy is a lamellar graphite cast iron.

A second aspect of the invention is a part made of an alloy as defined above. The piece is notably a tool. The tool may comprise only portions of the alloy according to the invention or be entirely made of this alloy. Generally at least the form surface of the tool consists of the alloy according to the invention.

Preferably, the tooling has a minimum wall thickness that is less than 50 mm.

A third aspect of the invention is the method of manufacturing a part made of an alloy according to the invention.

First of all the part, for example a tool, is cast in a mold.

Once the piece is poured into the mold, it undergoes cooling, including slow, in its mold. The term "slow" means less than 50 ° C / h, especially over the entire cooling period between casting of the part and solidification.

After the cooling step, the workpiece can be heat treated, for example by annealing.

The alloy is used in particular for the manufacture of tools used subsequently for the manufacture of composite parts, for example thermoplastic material and carbon fibers. The technical field can be aeronautics.

• Silicium (Si) entre 1,2% et 3%, et/ou
• Phosphore (P) ≤ 0,04%, et/ou
• Soufre (S) ≤ 0,03%.

According to other aspects of the invention, the alloy may comprise one or more of the following contents:

• Si (Si) between 1.2% and 3%, and / or
• Phosphorus (P) ≤ 0.04%, and / or
• Sulfur (S) ≤ 0.03%.

Claims (10)

1. Spheroidal graphite or flake graphite cast-iron alloy comprising the following elements in weight %:

   - Carbon (C) between 1.2 % and 3.5 %,

   - Silicon (Si) between 1.0 % and 3 %,

   - Nickel (Ni) between 26 % and 31 %,

   - Cobalt (Co) between 15 % and 20 %,

   optionally:

   - Magnesium (Mg) between 0.02 % and 0.10 %,

   - Manganese (Mn) ≤ 1.5 %,

   - Chromium (Cr) ≤ 0.5 %, and/or

   - Phosphorus (P) ≤ 0.12 or ≤ 0.04 %, and/or

   - Sulfur (S) ≤ 0.11 or ≤ 0.03 %, and/or

   - Molybdenum (Mo) ≤ 0.5 %, and/or

   - Copper (Cu) ≤ 0.5 %,

   the remainder being iron and inevitable impurities.
2. The alloy according to claim 1, wherein the Nickel (Ni) content is at least 27 % or 28 % and/or at most 30 %.
3. The alloy according to claim 1 or 2, wherein the Cobalt (Co) content is at least 16 % and/or at most 18 % or 19 %.
4. The alloy according to anyone of claims 1 to 3, comprising

   - at least 1.4 % or 1.5 % Carbon (C) and at most 3.1 % or 3.3 % Carbon (C) and/or

   - at least 1.4 % or 1.5 % Silicon (Si) and at most 2.6 % or 2.8 % Silicon (Si).
5. The alloy according to any one of the preceding claims, wherein the content of Manganese (Mn) is at least 0.01 % and/or at most 1.0 %.
6. The alloy according to any one of the preceding claims, wherein the content of Copper (Cu) is at most 0.2 %, 0.3 % or 0.4 %.
7. The alloy according to any one of the preceding claims, wherein the content of Molybdenum (Mo) is at most 0.2 %, 0.3 % or 0.4 %.
8. The alloy according to any one of the preceding claims, wherein the content of Chromium (Cr) is at most 0.3 %, 0.4 % or 0.5 %.
9. A part produced in a cast-iron alloy, characterized in that the alloy is an alloy according to any one of the preceding claims, in particular in that the part is a tool.
10. A method to produce a part according to claim 9, characterized in that it comprises the following steps:

    - Casting the part in a mould,

    - Once the part is cast in the mould, subjecting the part to cooling in the mould, in particular the step of cooling the part in the mould is cooling at a rate below 50°C/h.

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