PROCESS FOR MAKING A DIAMOND TOOL

Abstract

Disclosed is a process for making a diamond tool for processing ceramic starting from a mixture of aluminum-based powders in order to obtain a grinding wheel for an eco-friendly squaring of ceramic.

Claims

1. Process for making a diamond tool for processing ceramic starting from a mixture of aluminum-based powders, comprising the steps of: pressing of a mixture of powders (I) inside a mold so as to obtain a semi-finished product; pressing-sintering of the semi-finished product; finishing of the semi-finished product by performing also a thickening of the semi-finished product so as to obtain a finished product; wherein the mixture of powders includes (percentages by weight): at least 70% of aluminum, from 0 to 2.5% of a lubricant, and at least one powder component chosen among the following substances: copper, magnesium, silicon and zinc or mixtures thereof, copper being included between 0 and 10%.

2. The process according to claim 1, wherein the mixture of powders (I) includes from 0 to 5% by weight of magnesium.

3. The process according to claim 1, wherein the mixture of powders (I) includes from 0 to 20% of silicon.

4. The process according to claim 1, wherein the mixture of powders (I) includes from 0 to 10% of zinc.

5. The process according to claim 1, wherein the step of pressing-sintering is performed by heating the semi-finished product at a temperature comprised between 530 C. and 650 C. for a time comprised between 15 min. and 60 min.

6. The process according to claim 1, wherein the step of pressing-sintering is performed in pure nitrogen atmosphere.

7. The process according to claim 1, wherein after the pressing step, the semi-finished product is delubricated by heating the semi-finished product at a temperature comprised between 380 C. and 420 C. for a time comprised between 15 min. and 25 min.

8. The process according to claim 1, wherein the finished piece is subjected to at least one heat treatment.

9. The process according to claim 8, wherein the at least one heat treatment performed is at least one of the following treatments: sintering and cooling at ambient temperature; heating in air, subsequent rapid cooling in water and natural or artificial aging; hardening, cooling in water and artificial aging.

10. The process according to claim 1, wherein the pressing-sintering of the semi-finished product is performed directly on an aluminum support previously made.

11. The process according to claim 2, wherein the mixture of powders (I) includes from 0 to 20% of silicon.

12. The process according to claim 2, wherein the mixture of powders (I) includes from 0 to 10% of zinc.

13. The process according to claim 3, wherein the mixture of powders (I) includes from 0 to 10% of zinc.

14. The process according to claim 2, wherein the step of pressing-sintering is performed by heating the semi-finished product at a temperature comprised between 530 C. and 650 C. for a time comprised between 15 min. and 60 min.

15. The process according to claim 3, wherein the step of pressing-sintering is performed by heating the semi-finished product at a temperature comprised between 530 C. and 650 C. for a time comprised between 15 min. and 60 min.

16. The process according to claim 4, wherein the step of pressing-sintering is performed by heating the semi-finished product at a temperature comprised between 530 C. and 650 C. for a time comprised between 15 min. and 60 min.

17. The process according to claim 2, wherein the step of pressing-sintering is performed in pure nitrogen atmosphere.

18. The process according to claim 3, wherein the step of pressing-sintering is performed in pure nitrogen atmosphere.

19. The process according to claim 4, wherein the step of pressing-sintering is performed in pure nitrogen atmosphere.

20. The process according to claim 5, wherein the step of pressing-sintering is performed in pure nitrogen atmosphere.

Description

EXAMPLE 1

[0093] A mixture of powders (I) is subjected to a process for obtaining a mold and consists of (percentages by weight): [0094] 92.9% of aluminum, [0095] 4.5% of copper, [0096] 0.5% of magnesium [0097] 0.6% of silicon, and [0098] 1.5% of lubricant.

[0099] The mixture is put into a mold and the de-lubrication phase is performed at a temperature between 380 C. and 420 C., preferably at 400 C., for a time of 20 minutes.

[0100] Then, the sintering phase is performed at a temperature between 590 C. and 600 C. for a time of 20 minutes.

[0101] The properties of the so-obtained article are the following: the density of the sintered aluminum is 2.52 g/cm.sup.3, the dimensional variation is 0.4%, the tensile strength is 190 N/mm.sup.2 for T1, 260 N/mm.sup.2 for T4 and 320 N/mm.sup.2 for T6, wherein the hardness is 60 HB, 75HB and 100 HB, and the elongation A5 is 5% for T1, 3% for T4 and 1% for T6, respectively.

[0102] The so-obtained tool has a high mechanical resistance, a good dimensional stability and is suitable for the treatment of quench hardening and aging.

EXAMPLE 2

[0103] The procedure of Example 1 is repeated but the mixture of powders (I) consists of (percentages by weight): [0104] 96.8% of aluminum, [0105] 0.2% of copper, [0106] 1.0% of magnesium, [0107] 0.5% of silicon, and [0108] 1.5% of a lubricant.

[0109] The de-lubrication phase is performed at a temperature between 380 C. and 410 C., preferably at 395 C., for a time of 20 minutes.

[0110] The subsequent sintering phase is performed at a temperature between 630 C. and 635 C. for a time of 30 minutes.

[0111] The properties of the so-obtained article are the following: the density of the sintered aluminum is 2.47 g/cm.sup.3, the dimensional variation is 0.5%, the tensile strength is 140 N/mm.sup.2 for T1 and 230 N/mm.sup.2 for T6, wherein the hardness is 40 HB and 75 HB, and the elongation A5 is 5% for T1 and 3% for T6, respectively.

[0112] The so-obtained tool has an excellent corrosion resistance, a good mechanical resistance and ductility, and is suitable for anodizing.

EXAMPLE 3

[0113] The procedure of Example 1 is repeated but the mixture of powders (I) consists of (percentages by weight): [0114] 88.3% of aluminum, [0115] 1.7% of copper, [0116] 2.5% of magnesium, [0117] 6.0% of zinc, and [0118] 1.5% of a lubricant.

[0119] Besides, the de-lubrication phase is not performed because the sintering phase is performed at a temperature between 580 C. and 590 C. for a time of 60 minutes.

[0120] The properties of the so-obtained article are the following: the density of the sintered aluminum is 2.78 g/cm.sup.3, the dimensional variation is 1.5%, the tensile strength is 300 N/mm.sup.2 for T1 and 450 N/mm.sup.2 for T76, wherein the hardness is 100 HB and 150 HB, and the elongation A5 is 5% for T1 and 2% for T76, respectively.

[0121] The so-obtained tool has a high mechanical resistance.

EXAMPLE 4

[0122] The procedure of Example 3 is repeated but the mixture of powders (I) consists of (percentages by weight): [0123] 80.3% of aluminum, [0124] 2.6% of copper, [0125] 0.6% of magnesium, [0126] 15.0% of silicon, and [0127] 1.5% of a lubricant.

[0128] Also in this case, the de-lubrication phase is not performed because sintering occurs at a temperature between 580 C. and 590 C. for a time of 60 minutes.

[0129] The properties of the so-obtained article are the following: the density of the sintered aluminum is 2.67 g/cm.sup.3, the dimensional variation is 2.0%, the tensile strength is 200 N/mm.sup.2 for T1 and 280 N/mm.sup.2 for T6, wherein the hardness is 100 HB and 130 HB, and the elongation A5 is 1% for T1 and 0.5% for T6, respectively.

[0130] The so-obtained tool has a good wear resistance and good mechanical characteristics up to 200 C., as well as a low coefficient of thermal expansion.

[0131] According to the previous explanations, the excellent properties of aluminum-based alloys, the aluminum of which is suitably sintered and reprocessed with an appropriate thermal cycle or through a forging process (cold pressing of the sintered piece), enable to produce diamond tools of new concept which are ecological, light and performing.

[0132] With the aluminum-based formulation it is possible to avoid the problems of pollution caused by copper and bronze present in the waste from processing. This facilitates the waste disposal and provides the possibility of re-use the powders resulting from the processing.

[0133] Besides, the grinding wheel obtained with the process according to the invention weighs about half in comparison to a conventional metal grinding wheel, with significant benefits. One of the main benefits is the lower stress on the mechanics of the machine that supports and moves the grinding wheel.

[0134] According to a variant of the invention, it is possible to perform the sintering of aluminum directly on a body of the grinding wheel, which body acts as a support.

[0135] In fact, according to the prior art, in order to make the grinding wheel lighter, the metal band is sintered on an iron ring and then, it is coupled to an aluminum body. In the aluminum-based grinding wheel according to the invention, the cutting part can be sintered directly on the aluminum body so as to avoid some steps of the working with the result of being much lighter.

[0136] A technician of the sector can conceive modifications or variants which are to be considered as included in the scope of protection of the present invention.