JPS62174388A - Disk rotor and its production - Google Patents

Abstract

PURPOSE:To improve the wear resistance and heat resistance of the sliding surface of a disk rotor by disposing a metal (alloy) having a high tendency to form carbide on the sliding surface and irradiating high-density energy thereto, then subjecting the surface to the heat treatment under specific conditions. CONSTITUTION:The metallic element such as Cr or Mo or the alloy thereof having the higher tendency to form the carbide than Fe is disposed to the place of a cast iron disk rotor to be formed as the sliding surface. The high density energy is then irradiated thereto to quickly melt and quickly resolidify the metal or the alloy and to form the chilled alloy layer with 0.2-10wt% concn. of the above-mentioned metallic element. The chilled alloy layer is heated to the A1 transformation point or above and the solidus phase temp. or below and is then cooled. The alloyed cast iron layer of 250-400 HV hardness in which the base is pearlite or consists essentially of pearlite, the residual cementite exists at 2-15% and the lumped graphite is crystallized is formed to >=0.2mm depth. The disk rotor having the resistance to heat and wear and excellent workability and rust preventiveness is obtd. by the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a cast iron disc rotor (brake disc) used in disc brakes of automobiles, etc., and a method for manufacturing the same, and particularly to a method for manufacturing the disc rotor. This relates to improvements in properties and heat resistance.

2. Description of the Related Art Disc brakes have been widely used as brakes for automobiles and the like. One of the components of this disc brake is a disc rotor, which is a disc-shaped part against which brake pads are pressed to apply braking force. Since this disc rotor is a component against which the pads are pressed due to its rotating state, it is required to have high wear resistance.
In addition, it is required to have excellent heat resistance since it becomes high temperature due to frictional heat with the pad. As such disc rotors, those made of cast iron have been known for a long time, and the cast iron material for disc rotors is JIS
FC20 cast iron is used.

Problems to be Solved by the Invention As mentioned above, disc rotors become high in temperature due to frictional heat, but even in cast iron disc rotors, the A1
Temperatures may reach near the transformation point, and in this case, in conventional FC20 cast iron, pearlite near the surface decomposes, resulting in a decrease in hardness and a decrease in wear resistance.

In order to solve this problem, it may be possible to stabilize the pearlite structure by adding 0.3 to 0.5% of Cr, MO, etc. to FC20 cast iron. When alloying elements are added, the castability of the molten cast iron deteriorates significantly, causing difficulties in casting operations and inevitably causing problems. On the other hand, it is also possible to thermally spray a wear-resistant alloy such as high carbon Fe-Cr on the sliding surface of the disc rotor, but in this case there is a problem with the adhesion of the thermally sprayed layer, and after long-term use, The disadvantage is that the sprayed layer may peel off or become loose. Additionally, the conventional FC20 cast iron disc rotor had problems with its rust resistance.

This invention was made against the background of the above-mentioned circumstances, and it is possible to improve the wear resistance of the sliding surface without causing the above-mentioned problems.
The object of the present invention is to provide a disc rotor with improved heat resistance and a method for manufacturing the same.

Means for Solving the Problems The disc rotor of the present invention has a main body made of cast iron, and a sliding surface containing one or more metal elements having a higher tendency to form carbides than Fe in a total amount of 0.1. An alloyed cast iron layer containing ~10% by weight is formed over a depth of 0.2# or more, and the alloyed cast iron layer has pearlite or pearlite as a base and contains 2~15% by weight.
% of residual cementite is present, and the layer has a hardness of Hv 250 to 400 and is composed of a structure in which massive graphite is crystallized.

In addition, in the disc rotor manufacturing method of the present invention, after casting a disc rotor body using cast iron as a raw material, a metal element having a higher tendency to form carbides than Fe is added to the surface of a portion of the disc rotor body that is to become a sliding surface. A seed, two or more species, an alloy thereof, or an alloy of one or two or more thereof and iron is placed, and high-density energy is irradiated from above to cause rapid melting and rapid resolidification of the metal element. The total concentration of one or more of the following is 0.2 to 1.
The metal element was alloyed with cast iron to form a chilled alloy layer so that the metal element was 0% by weight, and then the chilled alloy layer was heated to a temperature range above the A1 transformation point and below the solidus temperature. A post-cooling heat treatment is performed to form an alloyed cast iron layer with a hardness of Hv 250-400 consisting of pearlite or pearlite-based base, 2-15% residual cementite, and crystallized massive graphite. It is characterized by being formed over a depth of .2# or more.

The cast iron that forms the main body of the disc rotor for
Normal cast iron such as No. 5 is preferable, but low alloy cast iron or the like may also be used. In addition, a trace amount of Ce is added to these for decomposition.
, Mg, etc. can also be added to cast iron.

In this invention, among the cast iron disc rotors made of ordinary cast iron, etc. as shown in (a) above, the parts that are particularly required to be 19mm resistant, that is, the parts that become the sliding surfaces for the brake pads, are made as described below. A layer of alloyed cast iron is formed over a depth of 0.2 m or more.

In addition to the cast iron component of the main body, this alloyed cast iron layer contains metal elements that have a higher tendency to form carbides than Fe, such as Or, Mo, W, Ta, Nb, ■, T1, Zr, or Mn. One or more metal elements are 0.2~
The content shall be within the range of 10% by weight. The structure of the alloyed cast iron layer is said to consist of pearlite (or pearlite-based structure) as a base, 2 to 15% residual cementite, and bulk crystallized graphite, and its hardness is It is said to be within the range of Hv 250-400.

As mentioned above, by containing metal elements with a high tendency to form carbides, such as Cr and MO, the alloyed cast iron layer on the sliding surface is strengthened by residual cementite in its structure and cementite constituting pearlite. stabilized, and the wear resistance and heat resistance are significantly improved compared to the case without these additions. That is, even if the sliding surface reaches a temperature close to the A1 transformation point due to frictional heat during use, the cementite does not decompose, and therefore the wear resistance does not deteriorate.

Here, if the content of carbide-forming elements such as Cr and MO in the alloyed cast iron layer is less than 0.2% by weight, the effect of strengthening cementite and improving wear resistance and heat resistance cannot be sufficiently obtained; If it exceeds 10% by weight, it becomes difficult to finally adjust the hardness and coarse weave as described above, so the content of the carbide-forming element was set within the range of 0.2 to 10% by weight. Note that within this range, a range of 0.5 to 3.0% by weight is particularly preferable.

Regarding the metallographic structure of the alloyed cast iron layer, in addition to alloying the carbide-forming elements, by creating the above-mentioned structure, it has excellent wear resistance and at the same time is less aggressive to the brake pad that is the sliding partner. Abrasion resistance) can be reduced, and workability is also improved, which is advantageous in terms of toughness and chipping is less likely to occur.

In other words, first of all, the pearlite base structure itself has an advantage in wear resistance compared to the ferrite base structure, and the presence of residual cementite in the base structure significantly improves the wear resistance. be. Here, if the residual cementite is less than 2%, sufficient wear resistance cannot be ensured. On the other hand, if the amount of residual cementite increases, it is advantageous only from the viewpoint of wear resistance, but the wear of the mating pad increases and the workability also decreases. According to experiments conducted by the inventors, in order to ensure the wear resistance of the disc rotor sliding surface, reduce the wear of the mating pad, and obtain excellent workability,
It has been found that it is necessary that the amount of residual cementite is 10% or less, and therefore the amount of residual cementite is set within the range of 2 to 10%. On the other hand, graphite that crystallizes in the structure has an advantage in terms of toughness compared to flake graphite such as ordinary cast iron because its shape is lumpy, and it can prevent chipping of the sliding surface. .

Regarding the hardness of the rough alloyed cast iron layer, H\L 250
Wood) Bacteria cannot ensure the wear resistance of the 8th surface, while the 11v
If the Hv exceeds 400, the mating pad will be excessively worn and the workability will also deteriorate, so it is necessary to keep the Hv within the range of 250 to 400.

If the depth of the alloyed cast iron layer, which has the above-mentioned components, structure, and hardness, is 0.2 m, sufficient wear resistance and heat resistance cannot be ensured, so the depth is 0-2t71j! It is necessary to set it to 1 or more.

As described above, an alloyed cast iron layer having a predetermined structure, a predetermined hardness, and a predetermined depth, which is alloyed with a predetermined amount of carbide-forming elements such as Or and MO, is formed on the sliding surface. This ensures the wear resistance of the disc rotor sliding surface itself, prevents wear of the mating pad, ensures workability, prevents chipping, and heat resistance (due to decomposition of cementite due to frictional heat during use). At the same time, we were able to ensure the prevention of wear resistance (deterioration of wear resistance).

It is preferable that the disc rotor also has excellent rust resistance, and if rust resistance is strongly required, a combination of Qr or Cr and other elements among the carbide-forming elements mentioned above may be used. This is desirable. In this case, the rust resistance of the alloyed cast iron layer is also significantly improved.

Next, a method for manufacturing a disc rotor having an alloyed cast iron layer as described above, that is, a second invention will be described.

First, the disc rotor body may be manufactured by casting using a cast iron material such as the above-mentioned ordinary cast iron as a raw material by a normal casting method such as sand casting.

First, using a high-density energy source, the obtained disc rotor body was treated with Cr, Mo, W, Ta, Nb, V,
Alloying treatment of carbide-forming elements such as Ti, Zri, or Mn is performed. That is, one or more of the above-mentioned carbide-forming elements, an alloy thereof, or one or more of these is applied to the surface of the driving surface of the disc rotor body, which requires particularly wear resistance and heat resistance. By irradiating high-density energy such as a laser, electron beam, plasma arc, or TIG arc onto the alloy, Cr, MO-specific carbide-forming elements, and other elements containing them are placed on the surface. The alloy and the surface layer of the cast iron base material underneath are instantly and rapidly melted to alloy the cast iron with carbide-forming elements such as Cr and MO, and then the molten alloy is melted by moving the energy irradiation position or stopping the irradiation. Rapidly solidifies the layer instantly. Here, the mass of the part melted by high-density energy irradiation is much smaller than the mass of the entire disc rotor, so by moving the high-density energy irradiation position or stopping the irradiation, heat transfer to the disc rotor base material side can be achieved. The molten alloy layer instantly solidifies),
It becomes a chilled alloy layer.

Specific methods for disposing carbide-forming elements such as Or and MO or alloys containing them on the sliding surface of the disc rotor include, for example, placing or thermal spraying their powders, compacts, thin plates, etc. Alternatively, it can be applied as a slurry, or it can be roughly formed into grooves in the necessary areas and filled into the grooves.

As mentioned above, when alloyed using high-density heating energy, a so-called chilled cast iron structure is formed in the alloy layer, which has a hardness of Hv 550 or more and is composed of cementite +
It shows a structure from 1 to roostite+martenthiae 1. This type of chilled cast iron structure is too hard, causing significant wear on the mating pad, and is brittle, easily chipping, and is even difficult to process, so it is used as is for the sliding surface of disc rotors. There are obstacles to doing so. Therefore, after the alloying process, the alloy layer of the chilled cast iron structure is
Heat treatment is performed to adjust the hardness and structure of the material. This heat treatment involves heating and holding in a temperature range above the A1 transformation point and below the solidus temperature to graphitize and partially decompose and agglomerate cementite, and in the subsequent cooling process Barley 1~ remains stable. be. The heating time in this heat treatment may range from several minutes to several tens of minutes, but the specific optimum temperature and time vary depending on the type of carbide-forming element alloyed, M, etc. That is, when a large amount of carbide-forming elements are added, or when the alloying elements added have a particularly strong tendency to form carbides (for example, Ti, Zr, Nb, etc.), heating must be carried out at high temperatures for long periods of time. Cooling conditions also vary depending on the amount and type of alloyed carbide-forming elements, but air cooling is usually sufficient.

In addition, in the above heat treatment, even if local heating that heats only the chilled alloy layer, such as high frequency induction heating or flame heating (burner 1'J mouth heat), the entire disc rotor is heated. Furnace heating for 7 JD may also be used.

As described above, by forming a chilled alloy layer of cast iron and carbide-forming elements such as Cr and MO on the surface layer by alloying treatment using high-density energy, and then applying heat treatment,
An alloyed cast iron layer having the structure and hardness as described above can be formed on the moving surface.

After the heat treatment described in (a)) and (e), machining processes such as grinding and polishing may be performed as needed to finally produce a disc rotor product.

Embodiment FIG. 1 shows the outline of a disc rotor 1 according to an embodiment of the present invention. In the first figure, 2 is the disc rotor body,
3 is an alloyed cast iron layer formed on the sliding surface. Examples of manufacturing such disc rotors are shown in the following [First Example], [Second Example], and [Third Example].

[First Example] First, a disc rotor main body having an outer diameter of 25 Q7 g4 was cast by sand casting using a molten JIS FC2Ql iron to which o, oi weight percent of Ce was added for the purpose of preventing blowholes. MO was applied to the sliding surface of the obtained disc rotor body in an amount of 0.1. Plasma sprayed on the instep.

Next, high-density energy by pulsed TIG arc was irradiated from above the MO sprayed layer to perform alloying treatment. This T
In the alloying process using the IG arc, argon gas was flowed into the treatment section as a shield gas at 151/min, and the TIG arc torch was moved once in the radial direction at a speed of 6rIvr1/SeO while rotating the disrotor body at 178 revolutions per minute. I did it. The base current of TIG arc is 70A.
, the peak current was 100A.

After performing the alloying treatment in this manner, a heat treatment was performed in which the entire disc rotor was heated in a nitrogen atmosphere furnace at 1000'Cx for 5 minutes and then air cooled. Afterwards, a finishing touch was applied.

According to this first example, a disc rotor was obtained in which an MO alloyed cast iron layer was formed on the sliding surface to a depth of 1.3#. A photograph of the metallographic structure of the alloyed cast iron layer is shown in Fig. 2. The structure of the alloyed cast iron layer in this case was pearlite + 10% residual cementite and decadal graphite, the Mo concentration was 1.2% by weight, and the hardness Hv was 195.

[Second Embodiment 1 C instead of Mo in the first tiger WFp, fil
A disc rotor was manufactured using the same method and under the same conditions as the first example, except that Cr was sprayed onto one drying surface of the disc rotor body in thicknesses of 0, 2, tn, and tn.

By this second example, a disc rotor was obtained in which an Or alloyed cast iron layer was formed on the sliding surface to a depth of 1.5 cm. The structure of the alloyed cast iron layer is pearlite +9
% residual cementite + massive graphite, and Cr
The concentration was 1.9% by weight, and the hardness Hv was 235.

[Third Example] The same method and conditions as in the first example, except that 1 was used instead of MO in the first example, and the heat treatment after the alloying treatment was heated at 1000'CX for 30 minutes. manufactured disc rotors.

By this third example, a disc rotor was obtained in which a Ti alloyed cast iron layer was formed on the sliding surface to a depth of 1.3 cm. The structure of the alloyed cast iron 13 is pearlite +
The residual cementite toner mass graphite was 15%, and the lower i concentration was 1.1% by weight.

Endurance tests (wear and tear) were conducted on the disc rotors obtained in the first, second and third examples above, as well as a disc rotor made of JIS FC20 cast iron that was not subjected to alloying treatment or heat treatment. test), rust resistance evaluation test, and friction coefficient measurement test (efficacy test). The conditions and results of each of these tests are shown below.

[Durability test] 50km at deceleration of 0.3G using each disc rotor
The test of decelerating and braking from /hr to OKm/hr was repeated 1000 times at a brake temperature of 50'C. When the amount of wear on the sliding surface of each disc rotor was investigated, the results shown in FIG. 3 were 1q. From FIG. 3, it can be seen that the disc rotors according to the embodiments of the present invention have significantly better wear resistance than the untreated comparative disc rotors.

[Rust Resistance Evaluation Test] A 5% t=73<'fi fog test was conducted for each disc rotor at 50°C for 15 hours, and the surface 8 ratio of the sliding surface was measured. As a result, the results shown in FIG. 4 were obtained. From FIG. 4, the disc rotor according to the embodiment of the present invention is
It can be seen that all of the disc rotors have poor rust resistance compared to the untreated comparative disc rotor, and in particular, the disc rotor of the second example alloyed with Cr has significantly superior rust resistance.

[Friction coefficient measurement test (effectiveness test)] Ceramic brake pads were used as the mating material for each disc rotor, and after the aforementioned durability test, the speed was 1100N.
/hr to perform a braking test with a deceleration of 0.3G, @
The history coefficient was investigated. As a result, the friction coefficient of the disc rotor sliding surface according to each embodiment of the present invention is μ= OJ
It was found that the coefficient of friction was about 5, which was comparable to that of the heat-treated comparative disk rotor, and therefore, it was found that there was no decrease in effectiveness due to alloying.

Effects of the Invention The cast iron disc rotor of this invention (well, 1) wear resistance of the operating surface 1. At the same time, it is possible to prevent a decrease in wear resistance caused by the decomposition of cementite due to high temperatures in cool heat, and it has good heat resistance. Moreover, it is not particularly aggressive against the opponent pad, has good workability, prevents chipping, and has good rust resistance, making it a long-established disc rotor for disc brakes. Use products with excellent performance.

In addition, in the cast iron disc rotor of the present invention, cast iron with excellent castability and low-emission properties such as ordinary cast iron can be used for the non-operating parts, so it is particularly disadvantageous in terms of cost as well as impairing castability and workability. Must not be. Furthermore, according to the disc rotor manufacturing method of the present invention, a disc rotor having excellent performance as described above can be practically provided.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing a disc rotor according to an embodiment of the present invention, and FIG. 2 is a photograph (40
Figure 3 shows the durability test results (sliding surface wear M) of the disc rotor according to each example and the comparative disc rotor.
FIG. 4 is a graph showing the rust resistance evaluation test results (surface rust rate) of the disc rotors according to each example and the comparative disc rotor. 1... Disc rotor, 2... Disc rotor body, 3... Alloyed cast iron layer.

Claims (2)

[Claims] (1) The main body is made of cast iron, and the sliding surface has an alloyed cast iron layer containing a total of 0.1 to 10% by weight of one or more metal elements that have a higher tendency to form carbides than Fe. 0
．． It is formed over a depth of 2 mm or more, and the alloyed cast iron layer has a hardness that consists of pearlite or pearlite-based base, 2 to 15% residual cementite, and crystallized massive graphite. Hv
A disc rotor characterized by having 250 to 400 layers. (2) After casting a disc rotor body using cast iron as a raw material, a metal element with a higher tendency to form carbides than Fe is added to the surface of the portion of the disc rotor body that is to become the sliding surface.
A seed, two or more species, an alloy thereof, or an alloy of one or two or more thereof and iron is placed, and high-density energy is irradiated from above to cause rapid melting and rapid resolidification of the metal element. The metal elements are alloyed with cast iron so that the total concentration of one or more of them is 0.2 to 10% by weight to form a chilled alloy layer, and then the chilled alloy layer is A_1. Heat treatment is performed by heating to a temperature range above the transformation point and below the solidus temperature, and then cooling to make the base pearlite or mainly pearlite.
A disc rotor characterized by forming an alloyed cast iron layer having a hardness of 250 to 400 Hv and having a structure in which ~15% residual cementite exists and crystallized massive graphite is formed over a depth of 0.2 mm or more, and its production. Method.