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(11) | EP 1 506 323 B1 |
| (12) | EUROPEAN PATENT SPECIFICATION |
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| (54) |
GRAY CAST IRON ALLOY AND CAST INTERNAL COMBUSTION ENGINE COMPONENT GRAUE GUSSEISENLEGIERUNG UND BRENNKRAFTMASCHINENGUSSBAUTEIL ALLIAGE DE FONTE GRISE ET COMPOSANT DE MOTEUR A COMBUSTION INTERNE MOULE |
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| Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). |
BACKGROUND OF THE INVENTION
1. Field of the invention
[0001] The present invention concerns a grey cast iron alloy. More specifically, the present invention concerns a pearlitic grey cast iron comprising further alloying elements for improved fatigue strength.
[0002] The invention further concerns an internal combustion engine component, cast from grey cast iron alloy according to the invention.
2. Description of the prior art
[0003] Grey cast iron is a most attractive material for e.g. internal combustion engine blocks for vehicles due to a relatively low cost and yet good to excellent performance. Compositions within quite a wide range are previously known, such compositions normally being a compromise between properties, such as tensile strength, wear properties etc., of the material as used and production properties, such as cost, machinability etc.
[0004] Thus, for cast internal combustion engine blocks a base material 0120 has a composition according to Table 1 below and a common standard alloy has a composition also according to Table 1, the Scania standard alloy providing a grey cast iron with a pearlitic structure and a sound (pore free) material due to a comparatively high carbon content.
[0005] However, although fully acceptable at present, an improved fatigue strength is today desirable as a complement to the present properties and would extend the possible use of such a prior art grey cast iron.
[0006] It is an object of the present invention to provide a grey cast iron with a comparatively sound structure and offering good machinability properties and having, in addition, a substantially improved fatigue strength compared to that of a standard alloy.
[0007] It is a further object of the present invention to provide a grey cast iron internal combustion engine component, such as an engine block, having a substantially improved fatigue strength compared to that of a standard alloy.
SUMMARY OF THE INVENTION
[0008] The object of the present invention is obtained by a grey cast iron according to the accompanying claim 1. Preferred embodiments are specified in the dependent claims.
[0009] Further, the object of the present invention is obtained by a grey cast iron internal combustion engine component according to the accompanying claim 4. Preferred embodiments are specified in the dependent claim.
BRIEF DESCRIPTION OF THE DRAWING
[0010] Fig. 1 shows Wöhler fatigue curves for a base alloy, a standard alloy and an alloy according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0011] In the following description all percentages given for elements in the alloys specified are given as percentage by weight.
[0012] The alloy according to the present invention is a grey cast iron having a pearlitic structure, the carbon content being 3.2 - 3.49 %. The comparatively high carbon content promotes a sound structure. Additions of 0.2 - 0.4 % chromium, having pearlite/carbide stabilizing properties, provides a fine pearlitic structure.
[0013] Additions of 0.1- 0.4 % molybdenum, 0.03 - 0.3 % vanadium, 0.007 - 0.015 % titanium and < 0.15 % niobium act, in addition to their carbide forming properties, as nuclei providing a fine pearlitic and flake graphite structure as cast (both as primary and secondary precipitated carbides). Molybdenum also stabilises pearlite at elevated temperatures.
[0016] Copper, here in an amount of 0.3 - 1.0 %, promotes pearlite formation and stabilizes the pearlite and also promotes the fine structure formation.
[0018] Nitrogen, 0.005 - 0.017 %, compacts flake graphite and promotes pearlite formation. Aluminium, < 0.01 %, act as graphite formation agent.
[0019] The grey cast iron alloy further comprises iron and normal impurities to balance. The amounts of titanium, nitrogen and aluminium are in the normal impurity range but may be preferred.
Examples:
[0020] 1500 kg batches were prepared, each batch being cast to four 300 kg engine blocks, casting starting at 1420°C and the temperature dropping about 10°C during the casting procedure.
[0021] Ten different combinations, batches, of molybdenum, vanadium, titanium and niobium, using a base alloy, were produced.
[0022] Further, the nitrogen and aluminium content was varied in 16 different batches with different nuclei forming agents (inoculants).
[0024] Still further, batches combining the composition showing the best results from the previous tests were produced and fatigue tested.
[0025] Results are shown in Fig. 1, curve 3 corresponding to compositions within the composition ranges according to the invention, this composition also being shown in Table 1.
[0026] The grey cast irons according to the invention offer about 40 % higher fatigue strength than a grey cast iron base alloy and about 30 % higher fatigue strength than a standard engine block grey cast iron and still offering a grey cast iron which fulfils high performance with respect to machinability, soundness, etc.
[0027] As mentioned above, the grey cast iron alloy according to the invention is extremely useful for internal combustion cast engine components, such as engine block components, the alloy combining machinability, soundness and high fatigue strength. The alloy is also useful for other components such as cylinder heads, etc.
| Alloy | |||||
| Compound | Base 0120 | Standard alloy | Invention in general | Preferred embodiment | Example alloy 3 of Fig. 1 |
| C | 3.2 - 3.5 | ∼3.4 | 3.2 - 3.49 | 3.3 - 3.4 | 3.37 |
| Si | 1.8 - 2.3 | ∼2.0 | 1.8 - 2.2 | 1.8 - 2.2 | 1.8 |
| S | 0.06-0.15 | < 0.14 | < 0.15 | < 0.1 | 0.1 |
| P | <0.20 | <0.10 | < 0.15 | < 0.05 | 0.05 |
| Mn | 0.6 - 0.8 | 0.6 - 0.8 | 0.3 - 0.8 | 0.4 - 0.6 | 0.68 |
| Cr | 0.2 - 0.35 | 0.2-0.4 | 0.2-0.4 | 0.34 | |
| Mo | 0.1 - 0.4 | 0.2 - 0.3 | 0.26 | ||
| V | 0.03 - 0.3 | 0.05 - 0.1 | 0.1 | ||
| Cu | 0.4 - 0.8 | 0.3 - 1.0 | 0.5 - 1.0 | 0.6 | |
| Ni | < 0.1 | < 0.1 | |||
| Ti | 0.007-0.015 | 0.007 -0.013 | 0.013 | ||
| Nb | < 0.15 | < 0.10 | 0.04 | ||
| N | 0.005-0.017 | 0.005-0.015 | 0.010 | ||
| Sn | < 0.1 | < 0.1 | |||
| Al | < 0.01 | < 0.01 | |||
1.8 - 2.2 % silicon
< 0.15 % sulphur
< 0.15 % phosphorus
0.3 - 0.8 % manganese
0.2 - 0.4 % chromium
0.1 - 0.4 % molybdenum
0.03 - 0.3 % vanadium
0.3 - 1.0 % copper
< 0.15 % niobium
0.007-0.015 % titanium
0.005-0.017 % nitrogen
Al < 0.01
Ni < 0.1
Sn < 0.1
the balance iron and impurities.
3.3 - 3.4 % carbon
1.8 - 2.2 % silicon
< 0.1 % sulphur
< 0.05 % phosphorus
0.4 - 0.6 % manganese
0.2 - 0.4 % chromium
0.2 - 0.3 % molybdenum
0.05 - 0.1 % vanadium.
1.8 - 2.2 % silicon
< 0.15 % sulphur
< 0.15 % phosphorus
0.3 - 0.8 % manganese
0.2 - 0.4 % chromium
0.1 - 0.4 % molybdenum
0.03 - 0.3 % vanadium
0.3 - 1.0 % copper
0.007 - 0.013 % titanium
< 0.15 % niobium
0.005 - 0.015 % nitrogen
< 0.01 % aluminium
Ni < 0.1
Sn < 0.1
the balance iron and impurities.
3,2 - 3,49 % Kohlenstoff
1,8 - 2,2 % Silizium
<0,15 % Schwefel
<0,15 % Phosphor
0,3 - 0,8 % Mangan
0,2 - 0,4 % Chrom
0,1 - 0,4 % Molybdän
0,03 - 0,3 % Vanadium
0,3 - 1,0 % Kupfer
<0,15 % Niob
0,007 - 0,015 % Titan
0,005-0,017 % Stickstoff
<0,01 % Aluminium
<0,1 % Nickel
<0,1 % Zinn
Rest Eisen und Verunreinigungen.
3,3 - 3,4 % Kohlenstoff
1,8 - 2,2 % Silizium
<0,1 % Schwefel
<0,05 % Phosphor
0,4 - 06 % Mangan
0,2 - 0,4 % Chrom
0,2 - 0,3 % Molybdän
0,05 - 0,1 % Vanadium.
3,2 - 3,49 % Kohlenstoff
1,8 - 2,2 % Silizium
<0,15 % Schwefel
<0,15 % Phosphor
0,3 - 0,8 % Mangan
0,2 - 0,4 % Chrom
0,1 - 0,4 % Molybdän
0,03 - 0,3 % Vanadium
0,3 - 1,0 % Kupfer
0,007 - 0,013 % Titan
<0,15 % Niob
0,005 - 0,015 % Stickstoff
<0,01 % Aluminium
<0,1 % Nickel
<0,1 % Zinn
Rest Eisen und Verunreinigungen.
1,8 à 2,2 % de silicium,
< 0,15 % de soufre,
< 0,15 % de phosphore,
0,3 à 0,8 % de manganèse,
0,2 à 0,4 % de chrome,
0,1 à 0,4 % de molybdène,
0,03 à 0,3 % de vanadium,
0,3 à 1,0 % de cuivre,
< 0,15 % de niobium,
0,007 à 0,015 % de titane,
0,005 à 0,017 % d'azote,
Al < 0,01
Ni<0,1
Sn<0,1
le restant étant constitué de fer et d'impuretés.
3,3 à 3,4 % de carbone,
1,8 à 2,2 % de silicium,
< 0,1 % de soufre,
< 0,05 % de phosphore,
0,4 à 0,6 % de manganèse,
0,2 à 0,4 % de chrome,
0,2 à 0,3 % de molybdène,
0,05 à 0,1 % de vanadium.
1,8 à 2,2 % de silicium,
< 0,15 % de soufre,
< 0,15 % de phosphore,
0,3 à 0,8 % de manganèse,
0,2 à 0,4 % de chrome,
0,1 à 0,4 % de molybdène,
0,03 à 0,3 % de vanadium,
0,3 à 1,0 % de cuivre,
0,007 à 0,013 % de titane,
< 0,15 % de niobium,
0,005 à 0,015 % d'azote,
< 0,01 % d'aluminium
Ni < 0,1
Sn<0,1
le restant étant constitué de fer et d'impuretés.