TIRE STUDS

Abstract

A tire stud made of a cemented carbide including at least 50 wt % WC and a metal binder in the amount between 3 and 25 wt % is provided. The metal binder includes at least 30 wt % Ni and less than 50 wt % Co. The use of such tire studs leads to less wear of the road surface.

Claims

1. A tire stud made of a cemented carbide comprising at least 50 wt % WC and a metal binder in an amount between 3 and 25 wt %, wherein the metal binder includes at least 30 wt % Ni and less than 50 wt % Co.

2. The tire stud according to claim 1, wherein the metal binder includes at least 50 wt % Ni.

3. The tire stud according to claim 1, wherein the metal binder includes Fe in an amount of at least 5 wt %.

4. The tire stud according to claim 1, wherein the metal binder includes less than 15 wt % Co.

5. The tire stud according to claim 1, wherein the cemented carbide is free from Co.

6. The tire stud according to claim 1, wherein the metal binder includes Fe and Ni so that the total amount of Fe+Ni is at least 80 wt % of the metal binder.

7. The tire stud according to claim 1, wherein the metal binder includes between 80 and 90 wt % Ni and between 10 and 20 wt % Fe.

9. The tire stud according to claim 1, wherein the metal binder includes Cr in an amount of between 1 and wt % of the binder.

Description

DESCRIPTION OF DRAWINGS

[0026] FIGS. 1 and 2 describes filters that collected particles from the tests in Example 2. FIG. 1 shows the filters from when the prior art studs were tested whereas FIG. 2 shows the filters from when the studs according to the invention were tested.

[0027] FIGS. 3 and 4 describes filters that collected particles from the tests in Example 3. FIG. 3 shows the filters from when the prior art studs were tested whereas FIG. 4 shows the filters from when the studs according to the invention were tested.

EXAMPLE 1

[0028] Tire studs were manufactured from the amount of raw material as described in table 1. The tire studs according to the present invention, comprising a NiFe binder is herein denoted Invention 1, whereas the tire studs with a Co binder were commercially available, and are denoted Comparative 1. The amount of metal binder differs between Invention 1 and Comparative 1 since the same hardness of the tire stud was aimed for.

TABLE-US-00001 TABLE 1 WC Ni Fe Co Cr (wt %) (wt %) (wt %) (wt %) (wt %) Invention 1 Bal. 9.07 1.72 0.06 Comparative 1 Bal. 0.22 10.85 0.08

[0029] The tire studs were manufactured by mixing all the powder raw materials together with a water/ethanol milling liquid. The slurry was then milled for 50 hours followed by spray drying. The material was then subjected to a pressing operation forming green bodies in the shape of tire studs. The green bodies were then sintered in vacuum at 1410 C.

TABLE-US-00002 TABLE 2 HV30 Density (g/cm.sup.3) Invention 1 1173 14.45 Comparative 1 1177 14.46

EXAMPLE 2

[0030] The wear of the road surface by the different tire studs was then investigated by a pin on disc method. Three different stone materials were used, stone 1, 2 and 3.

[0031] The stud was mounted in the equipment and the stone plate (80 mm80 mm15 mm) representing the road surface was attached to a rotor. When testing the studded tire samples, the orientation of the stud was perpendicular to the sliding direction, as in real tire-on-road contacts.

[0032] The rotating speed for the stone plate was 45 rpm and the total sliding distance for the tire stud was 50 m and the test were repeated 4 times.

[0033] The pin-on-disc machine was in a sealed chamber to avoid contamination. The room air was drawn by a fan and entered the chamber through a filter. The particles in the air coming out of the chamber was then analyzed by an optical particle analyzer, TSI Optical Particle Sizer 3330.

[0034] The total particle concentration/sliding distance (#/cm.sup.3/m) was measured.

[0035] The results are shown in table 3 where each value is an average of 4 tests.

TABLE-US-00003 TABLE 3 Stone 1 Stone 2 Stone 3 Invention 1 56.9 47.0 60.9 Comparative 1 87.8 57.0 92.7

[0036] The loss of mass/sliding distance (g/m) was also measured. This was done by weighing the stone plates before and after the test. The results are shown in table 4 where each value is an average of 4 tests.

TABLE-US-00004 TABLE 4 Stone 1 Stone 2 Stone 3 Invention 1 15.2 10.2 13.7 Comparative 1 19.7 12.7 20.3

[0037] The particles were also detected by placing filters at the outlet of the sealed chamber when the pin-on-disc examples were performed. The filters collected particles of different sizes, 1 m, 2.5 m and 10 m respectively. FIG. 1 shows the particles that was accumulated from all three stone types when the studs according to prior art, Comparative 1, were tested. FIG. 2 shows the particles that was accumulated from all three stone types when the studs according to the invention, Invention 1, were tested. It can clearly be seen that the studs according to the invention generates far less particles that the prior art studs.

EXAMPLE 3

[0038] The wear on the road surface caused by the different tire studs was then investigated by a pendulum rig tester.

[0039] The same type of tire studs as described in Example 1 were used in this test. The tire studs were mounted onto tires. From the tires, pieces were cut out including two studs each.

[0040] The equipment is arranged so that when the pendulum, where the tire pieces with the studs has been mounted, is released from a horizontal position, it will strike the stone material with a constant velocity. Two types of stone materials were tested, stone 2 from example 2, and a fourth type, stone 4.

[0041] The stud was mounted at the tip of the pendulum in the equipment and the stone plate (80 mm80 mm15 mm) representing the road surface was mounted in the bottom of the equipment. The stone material was hit 200 times and the distance each time was 0,125 m which gives a total distance of 25 m.

[0042] The pendulum rig tester was placed in a sealed chamber to avoid contamination. The room air was drawn by a fan and entered the chamber through a filter. The particles in the air coming out of the chamber were then analyzed in the same way as in Example 2.

[0043] The test was repeated 3 times and the average of those tests are shown in Table 5, where the total particle concentration/sliding distance (#/cm.sup.3/m) is shown, and Table 6, where the loss of mass/sliding distance (g/m) is shown.

TABLE-US-00005 TABLE 5 Stone 2 Invention 1 39 Comparative 1 51

TABLE-US-00006 TABLE 6 Stone 2 Stone 4 Invention 1 8.2E05 0.00092 Comparative 1 0.00033 0.0015

[0044] Like in Example 2, particles were also detected by placing filters at the outlet of the sealed chamber when the pendulum tests were performed. The filters collected particles of different sizes, 1 m, 2.5 m and 10 m respectively. FIG. 3 shows the particles that was accumulated from both stone types for the studs according to prior art, Comparative 1. FIG. 4 shows the particles that was accumulated from both stone types when the studs according to the invention, Invention 1, were tested. It can clearly be seen that the studs according to the invention generates far less particles that the prior art studs.