Gray iron castings for disc brake parts

Abstract

A grey cast iron, particularly for disc brake components. The invention comprises in an iron matrix carbon in an amount of 3.60-3.90% by weight, silicon in an amount of 1.40-1.90% by weight, titanium in an amount of 0.10% by weight or less, manganese in an amount of 1.0-1.5% by weight, nickel in an amount of 0.20% by weight or less, chromium in an amount between 0.40% and 1.0% by weight, copper in an amount not exceeding 0.35% by weight, phosphorus in an amount not exceeding 0.10% by weight, sulfur in an amount not exceeding 0.12% by weight, tin in an amount not exceeding 0.10% by weight, and molybdenum in an amount not exceeding 0.10% by weight.

Description

[Technical field]

[0001] The present invention relates to a cast iron, in particular for producing discs for disc brakes, and to discs produced from said cast iron. [Background technology]

[0002] Discs for disc brakes made of grey cast iron are subject to wear phenomena, especially in the brake bands, which, in addition to inevitably affecting the durability of the discs, contribute to the emission of PM10 particulate matter into the atmosphere, with adverse effects on the environment and human health.

[0003] In fact, as brake discs wear, micrometer-sized metal particles generated by the friction of the discs against the pads are released into the environment. Some of these particles adhere to the wheel rim, others fall to the ground or become suspended in the air. Brake wear debris therefore constitutes a significant source of air pollution.

[0004] Therefore, there is a strong need for grey cast iron brake discs with high wear resistance in the automotive industry, especially for high performance vehicles such as luxury cars and racing motorcycles and for extreme braking applications.

[0005] Indeed, improved wear resistance extends the life of the brake discs and reduces the emission of metal dust into the environment.

[0006] Brake discs are subjected to high mechanical and thermal stresses, which can result in the brake band reaching high temperatures that can lead to a reduction in braking performance, even if cracks do not form in the brake band.

[0007] The problem underlying the present invention is therefore to provide a grey cast iron that is able to exhibit high wear resistance without adversely affecting its mechanical strength. Summary of the Invention

[0008] The above problems are solved by a grey cast iron as well as a disc for disc brakes, as outlined in the appended claims, the definitions of which form an integral part of this specification.

[0009] The grey cast iron of the present invention advantageously exhibits higher wear resistance, which can dramatically reduce PM10 particulate matter emissions into the atmosphere, thereby benefiting the environment and human health.

[0010] Further features and advantages of the invention will become apparent from the description of some embodiments given below, given by way of non-limiting indication. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The subject of the present invention is a grey cast iron containing, in an iron matrix, carbon, silicon, titanium, manganese, nickel, chromium, copper, phosphorus, sulfur, tin and molybdenum. These alloying elements are contained in the grey cast iron according to the invention in the following weight percentages: 3.60-3.90% by weight carbon; 1.40-1.90% by weight silicon; not more than 0.10% by weight titanium; 1.0% to 1.5% by weight manganese; not more than 0.20% by weight nickel; 0.40% by weight or more and 1.0% by weight or less of chromium; not more than 0.35% by weight copper; not more than 0.10% by weight phosphorus; not more than 0.12% by weight sulfur; Not more than 0.10% by weight tin; Molybdenum in an amount not exceeding 0.10% by weight.

[0012] Optionally, the grey cast iron may further comprise vanadium in an amount not exceeding 0.05% by weight, such as not exceeding 0.04% by weight, or not exceeding 0.03% by weight, or not exceeding 0.02% by weight, or not exceeding 0.01% by weight.

[0013] In said grey cast iron, the carbon is in the form of graphite.

[0014] Preferably, the amount of carbon is 3.65-3.85 wt%, more preferably 3.70-3.80 wt%, and even more preferably 3.75-3.80 wt%.

[0015] Preferably, the amount of silicon is between 1.50 and 1.80 wt%, more preferably between 1.50 and 1.70 wt%, even more preferably between 1.60 and 1.65 wt%.

[0016] Preferably, the amount of titanium is up to 0.08 wt%, more preferably between 0.03 and 0.07 wt%, and even more preferably between 0.04 and 0.06 wt%.

[0017] Preferably, the amount of manganese is 1.0-1.3% by weight, preferably 1.1-1.2% by weight.

[0018] Preferably, the amount of nickel is not more than 0.10 wt%, such as not more than 0.08 wt%, 0.07 wt%, 0.06 wt%.

[0019] Preferably, the amount of chromium is 0.50-0.90 wt.%, more preferably 0.50-0.60 wt.%.

[0020] Preferably, the amount of copper is less than 0.30 wt%, more preferably 0.10-0.30 wt%, and even more preferably 0.20-0.30 wt%.

[0021] Preferably, the amount of phosphorus is less than or equal to 0.08 wt%, more preferably 0.02-0.07 wt%, and even more preferably 0.03-0.05 wt%.

[0022] Preferably, the amount of sulfur is less than or equal to 0.10 wt%, more preferably 0.05-0.09 wt%, and even more preferably 0.07-0.08 wt%.

[0023] Preferably, the amount of tin is up to 0.08 wt%, more preferably between 0.02 and 0.07 wt%, and even more preferably between 0.03 and 0.05 wt%.

[0024] Preferably, the amount of molybdenum is up to 0.08 wt%, more preferably 0.02-0.07 wt%, and even more preferably 0.03-0.05 wt%.

[0025] Preferably, said grey cast iron consists or essentially consists of said alloying elements and said iron matrix, i.e. with respect to the amounts of alloying elements defined above, the remaining weight amount of the grey cast iron consists or essentially consists of said iron matrix. The phrase "consists essentially of" indicates that the grey cast iron of the present invention may contain impurities such as boron, tungsten and / or aluminum in amounts of less than 0.01% by weight each in addition to the aforementioned alloying elements and iron matrix, and preferably the grey cast iron of the present invention contains impurities in an amount of less than 0.01% by weight overall.

[0026] According to one embodiment of the present invention, the grey cast iron has the following composition: 3.77% by weight carbon; 1.63% by weight silicon; 0.0512% by weight titanium; 0.0069% by weight vanadium; 1.14% by weight manganese; 0.0535% by weight nickel; 0.502% by weight chromium; 0.237% by weight copper; 0.0307% by weight phosphorus; 0.0708% by weight sulfur; 0.037% by weight tin; 0.0362% by weight molybdenum. The remaining amount consists essentially of the iron matrix.

[0027] Preferably, the grey cast iron of the invention is of the fine lamellar type, the carbon contained therein being mainly in the form of lamellar graphite. Preferably, said grey cast iron consists of fine lamellae of graphite belonging to the category indicated by the Roman numeral "I". Preferably, the graphite lamellae have a size indicated by the reference numerals 3-8, preferably 3-5. The shape and size of said graphite are as classified in the standard UNI EN ISO 945-1.

[0028] Preferably, the iron matrix of the grey cast iron is of the pearlitic type.

[0029] Preferably, the grey cast iron comprises not less than 95% by weight of pearlite relative to the weight of the iron matrix, preferably, the grey cast iron comprises more than 95% by weight of pearlite relative to the weight of the iron matrix, or more than 96% by weight of pearlite relative to the weight of the iron matrix, or more than 97% by weight of pearlite relative to the weight of the iron matrix, or more than 98% by weight of pearlite relative to the weight of the iron matrix, or more than 99% by weight of pearlite relative to the weight of the iron matrix.

[0030] Preferably, the grey cast iron comprises ferrite in an amount not exceeding 5% by weight relative to the weight of the iron matrix. According to various embodiments, the grey cast iron comprises ferrite in an amount less than 5% by weight, or less than 4% by weight, or less than 3% by weight, or less than 2% by weight, or less than 1% by weight relative to the weight of the iron matrix. According to a preferred embodiment, the grey cast iron comprises ferrite in an amount of about 1% by weight relative to the weight of the iron matrix. According to another preferred embodiment, the grey cast iron does not comprise ferrite.

[0031] Preferably, the grey cast iron comprises cementite and free carbides in an amount not exceeding 5% by weight based on the weight of the iron matrix. According to various embodiments, the grey cast iron comprises cementite and free carbides in an amount less than 5% by weight, or less than 4% by weight, or less than 3% by weight, or less than 2% by weight, or less than 1% by weight based on the weight of the iron matrix. According to preferred embodiments, the cast iron comprises cementite and free carbides in an amount not exceeding 1% by weight, or less than 1% by weight based on the weight of the iron matrix.

[0032] Advantageously, the grey cast iron of the invention can be used for the manufacture of disc brake parts. Advantageously, the grey cast iron of the invention can be used for the manufacture of at least one braking zone of a disc for any type of disc brake.

[0033] Experimental Testing

[0034] Experimental wear tests were carried out comparing brake discs made from grey cast iron according to the invention (Example 1) with brake discs made from grey cast iron to which the invention does not apply (Comparative Example).

[0035] Comparative Example

[0036] Brake discs were manufactured from grey cast iron having the following composition: 3.74% by weight carbon; 1.65% by weight silicon; 0.55% by weight manganese; 0.1% by weight nickel; 0.15% by weight chromium; 0.1% by weight molybdenum; 0.2% by weight copper; less than 0.1% by weight sulfur; less than 0.08% by weight phosphorus; 0.023% by weight tin; less than 0.09% by weight titanium; the remaining part by weight being an iron matrix consisting of 1% by weight ferrite, 98.5% by weight pearlite and 0.5% by weight carbides.

[0037] Hereinafter, the brake disc made of gray cast iron is referred to as the "comparative disc."

[0038] Working Example

[0039] Brake discs identical to the comparative discs, but using grey cast iron according to the invention, were manufactured having the following composition: 3.77% by weight carbon; 1.63% by weight silicon; 0.0512% by weight titanium; 0.0069% by weight vanadium; 1.14% by weight manganese; 0.0535% by weight nickel; 0.502% by weight chromium; 0.237% by weight copper; 0.0307% by weight phosphorus; 0.0708% by weight sulphur; 0.037% by weight tin; 0.0362% by weight molybdenum; the remaining parts by weight essentially consisting of an iron matrix.

[0040] The iron matrix consists of 99.10% by weight of pearlite and 0.90% by weight of carbides. The graphite lamellae belong to category "I" as defined above and have dimensions indicated by reference numerals 3 to 5 as defined above.

[0041] A brake disc made from such gray cast iron will hereinafter be referred to as "Disc 1".

[0042] Experimental Testing

[0043] The "comparative disc" and "disc 1" according to the invention were subjected to multiple repetitions of the WLTP test (1 hour conditioning with air at 20°C and 50% relative humidity + 303 stops (approximately 7.5 hours of testing) + cooling) to detect PM10 emissions. The parameters used were as follows:

[0044] Average braking speed: 43.7km / h; Deceleration: 0.49-2.18m / s 2 ; Average deceleration: 0.97m / s 2 ; BT ("Brake Temperature"): <40℃ to 175℃; Number of stops: 303; Total distance: 192km.

[0045] At the end of such a test, the mass loss of the two disks ("disk mass loss") was measured with the following results: Comparison disc: 9.0 grams mass loss; Disk 1: Mass loss of 4.9 grams.

[0046] As a result, under the same conditions, "Disc 1" experienced a mass loss that was significantly lower than the mass loss experienced by the "Comparative Disk."

[0047] In addition, the PM10 emission coefficients [mg km- 1 wheel -1 ] was also derived. Comparison disc: PM10 emission factor (PM10 EF) 1.92mg km-1wheel -1 ; Disk 1": PM10 emission factor (PM10 EF) is 0.62 mg km -1 wheel -1 .

[0048] The results showed that the PM10 emission coefficient of "Disk 1" was significantly lower than that of the "Comparison Disk."

[0049] From the above results it is clear that the grey cast iron according to the invention exhibits advantageously higher wear resistance than the standard grey cast iron taken as reference, thus enabling a significant reduction in PM10 particulate matter emissions into the atmosphere.

[0050] "Disc 1" and "Comparative Disk" were further characterized from a mechanical standpoint and in terms of functional parameters. The results are shown in Table 1:

[0051] [Table 1]

[0052] Comparison of the data shown in Table 1 reveals that the mechanical strength performance of "Disc 1" is substantially equivalent to that of the "Comparative Disk."

[0053] As can be seen from the above description, the gray cast iron of the present invention can overcome the shortcomings of the prior art.

[0054] In particular, the cast iron according to the invention and corresponding brake discs made from said cast iron provide significantly higher wear resistance compared to the standard grey cast iron taken as reference, and dramatically reduce the emissions of PM10 particulate matter into the atmosphere, and this is done without resulting in a decrease in mechanical strength.

[0055] It is obvious that only one particular embodiment of the invention has been described, and a person skilled in the art can make all the necessary modifications to adapt the cast iron and brake disc to his particular conditions, without departing from the scope of protection defined in the appended claims.

Claims

1. A grey cast iron containing carbon, silicon, titanium, manganese, nickel, chromium, copper, phosphorus, sulfur, tin and molybdenum in an iron matrix, The amount of carbon is 3.60-3.90% by weight; The amount of silicon is 1.40-1.90 wt.%; titanium in an amount of not more than 0.10 wt.%; the amount of manganese is 1.0% to 1.5% by weight; an amount of nickel not exceeding 0.20% by weight; chromium content of 0.40% by weight or more and 1.0% by weight or less; Copper not exceeding 0.35% by weight; the amount of phosphorus is not more than 0.10% by weight; the amount of sulfur is not more than 0.12% by weight; the amount of tin is not more than 0.10% by weight; The amount of molybdenum is not more than 0.10% by weight.

2. 10. The cast iron of claim 1, further comprising up to 0.05 wt. % vanadium.

3. 3. Cast iron according to claim 1 or 2, in which the amount of carbon is 3.65-3.85% by weight.

4. 3. Cast iron according to claim 1 or 2, wherein the silicon content is 1.50-1.80% by weight.

5. 3. A cast iron according to claim 1 or 2, in which the amount of titanium is less than or equal to 0.08% by weight.

6. 3. A cast iron according to claim 1 or 2, in which the amount of manganese is 1.0-1.3% by weight.

7. 3. A cast iron according to claim 1 or 2, in which the amount of nickel is less than or equal to 0.10% by weight.

8. 3. A cast iron according to claim 1 or 2, in which the amount of chromium is 0.50-0.90% by weight.

9. 3. A cast iron according to claim 1 or 2, in which the amount of copper is less than or equal to 0.30% by weight.

10. 3. A cast iron according to claim 1 or 2, in which the amount of phosphorus is not more than 0.08% by weight.

11. 3. Cast iron according to claim 1 or 2, in which the amount of sulfur is less than or equal to 0.10% by weight.

12. 3. A cast iron according to claim 1 or 2, in which the amount of tin is equal to or less than 0.08% by weight.

13. 3. A cast iron according to claim 1 or 2, in which the amount of molybdenum is less than or equal to 0.08% by weight.

14. 3. A cast iron according to claim 1 or 2, wherein the remaining amount consists of iron matrix.

15. 3. A cast iron according to claim 1 or 2, wherein said grey cast iron is of the fine lamellar type.

16. 3. A cast iron according to claim 1 or 2, wherein the iron matrix of said grey cast iron is of the pearlitic type.

17. 3. A cast iron according to claim 1 or 2, comprising ferrite in an amount lower than 5% by weight relative to the weight of the iron matrix.

18. 3. A cast iron according to claim 1 or 2, comprising cementite and free carbides in an amount of less than or equal to 1% by weight relative to the weight of the iron matrix.

19. A disc for a disc brake, comprising a braking band made of grey cast iron according to claim 1 or 2.

20. A cast iron according to claim 3, wherein the amount of carbon is 3.70-3.80% by weight.

21. The cast iron of claim 4, wherein the silicon content is 1.50-1.70 wt. %.

22. A cast iron according to claim 5, wherein the amount of titanium is 0.03-0.07% by weight.

23. The cast iron of claim 6, wherein the amount of manganese is 1.1-1.2 wt. %.

24. The cast iron of claim 8, wherein the amount of chromium is 0.50-0.60% by weight.

25. The cast iron of claim 9, wherein the amount of copper is 0.10-0.30% by weight.

26. A cast iron according to claim 15, wherein the grey cast iron contains fine lamellae of graphite belonging to the category indicated by the Roman numeral "I" according to standard UNI EN ISO 945-1.

27. The cast iron of claim 16, wherein the weight percentage of pearlite is 95% or less based on the weight of the iron matrix.