JPS5970748A - Hot-rolled platelike material of low carbon martensitic stainless steel with superior toughness for disk brake for motorcycle - Google Patents

Abstract

PURPOSE:To provide a sufficiently low ductility-brittleness transition temp. and necessary hardness to the resulting titled material and to improve the corrosion and wear resistances, by hardening a hot-rolled platelike material of a low carbon alloy steel contg. N, Mn, Cr and B. CONSTITUTION:This hot-rolled platelike material of a low carbon martensitic stainless steel with superior toughness for a disk brake for a motorcycle has a composition consisting of, by weight, 0.04-0.10% C+N, 0.5-2.5% Mn, 10.0- 14.5% Cr, 0.0005-0.010% B and the balance essentially Fe. The low carbon martensitic stainless steel is refined, hot rolled, blanked, and ground to finish a disk brake for a motorcycle, and the brake is hardened.

Description

[Detailed Description of the Invention] The present invention seeks to propose a hot-rolled copper sheet material for motorcycle disc brakes that is rich in terms and can be well adapted to the performance of the use of motorcycle disc brakes. It is.

Stainless steel is generally used for motorcycle brake discs, but it is required to have sufficient corrosion resistance, wear resistance, and toughness.

Traditionally, stainless steel used for this type of application is
16% ar-o, a%C and C: 0.2% (% is weight 61
0%; 5US420J engineering and c:
A medium C martensitic stainless steel such as 5US420J2fi with o, a% of
It is customary to perform heat treatment such as quenching from 900° to 1.00”O or quenching and tempering so that Rc is in the range.

However, in such conventional steel, C forging in the steel is 0.
Since the content is quite high, such as 2 to 0.3%, not only quench cracks often occur during quenching in the disk manufacturing process, but also the toughness after quenching is low, leaving a safety disadvantage.

The inventors first reduced the amount of C in the 3r steel by 18% (reduced the amount of Mn in the 3r steel), with the aim of providing the necessary hardness with high toughness through a simple heat treatment that involves only quenching from high temperatures. We proceeded with the development of a higher grade of steel and filed a patent application in 1988-8813.
Invention No. 2 - 1) 9 proposals have been made, but even with such 9A, the ductility-brittle transition temperature in the Charpy test is "below room temperature" - and the toughness cannot necessarily be sufficiently high. There wasn't.

In this way, in the current trend where emphasis is placed on the safety of automobile brake equipment, further research has been conducted with a focus on steel grades with even higher toughness that can effectively meet these demands. As a result, J3%Q with lower C
Addition of B to r steel [1i! Or, in addition to the addition of B, a small amount of i, (
] REM, Oa, V, Nb, Ti'(
It has been found that by adding one or more types of i=, the toughness of the disk during quenching is significantly improved.

This investigation is based on the above findings.
30 with only simple heat treatment of quenching fL from the temperature range of 0.
~40 Stable HRC hardness? We have proposed a new low carbon martensitic stainless steel that can be used for automatic fluid disc brakes and has excellent toughness even after heat treatment. (difficult, gu, overcome)] [i L

In this invention, the total amount is 0.04% to 0.10%.(0+N)'k, 0.5 to 2. ．． 5% Mn and 10
．． 0-1 move, 5% cr and 0.0005-0.01
With 0% B and optionally also up to 0.20% REM.

0.010% or less aa and 0.050% each
Contains at least tIti selected from the following V, Nb, and Ti, and the remainder is an unavoidable mixed component and Fe, and is a plate material that has undergone hot rolling, except for appropriate punching and grinding. By simply applying heat treatment such as quenching, it not only satisfies the hardness required for motorcycle disc brakes with sufficient corrosion resistance and abrasion resistance, but also has excellent toughness and is suitable for brake machine hhi. The above-mentioned issue 1 is to provide properties that can ensure safe continuation of the This is used as a means of determining uN.

The reason for limiting the components of the low carbon martensitic yarn suanless steel hot daughter plate material of this invention will be explained.

0 and N: total amount 0.04 to 0.10% C and N are elements that contribute to hardness and improve wear resistance, especially when quenched hardness is 30 to 40%. HRC
As described below, 0.5 to 2.5% Mn is essential to achieve this, but within this range In! : In order to achieve a hardness of 80 to 40HH (3) during quenching, the total amount of C and N must be in the range of 0.04 to 0.10%.

Mn: o, 5 to 2.5% Mn is an essential element for stabilizing hardening hardness during quenching from the warm range of 900 to 1100°C, and has a content of 0.
If it is less than 5%, even if quenching is performed from a temperature range of 9,000 to 1,100°C, the quenching hardness will not only change greatly depending on the change in the quenching temperature, but also the quenching temperature of 30 to 40 HRC, especially if the amount of (0+N) is low. Since the hardness cannot be obtained, the lower limit is set at 0.5%.If Mn exceeds 2.5%, the oxidizing property at high temperatures decreases, and scale formation during the steel sheet manufacturing process increases. , since there is a risk of significantly reducing dimensional accuracy, the upper limit was limited to 2.5%.

Or: 10.0 to 14.5% Qr must be at least 10.0% in order to maintain corrosion resistance. However, when it exceeds 14.5%, (0+N) becomes 0.
Even if the upper limit of Mn k is added in the range of 0.04 to 0.10%, the quenching hardness of 80 to 40 I (Re) cannot be obtained during quenching from the temperature range of 900 to 1100 °C, so the upper limit '514 It was limited to .5%.

B: 0.0005 to 0.010% B is useful for significantly increasing the toughness of the hardened steel sheet, and is an essential element for this invention. In order to stably maintain the ductility-brittle transition temperature below room temperature in the Charpy test, B must be at least 0.0005%, and the lower limit is 0.
0005%. However, if it exceeds 0.010%, the oxidation resistance at high temperatures will decrease, and scale formation will increase in the steel sheet manufacturing process, causing a decrease in the dimensional accuracy of the steel sheet, so the upper limit was set at 0.010%.

REM≦0.20%, ca≦0.10%, V,
Nb and Ti ≦ 0.050% in addition to the addition of B on top of REM, Oa, V,
The addition of one or more types of Nb and Ti is equally effective in improving the toughness of the steel sheet during quenching, and they bring about the same effects.

However, if LREM exceeds 0.20% and aa exceeds 0.010%, cracks will easily occur during the production of steel sheets, significantly reducing yield, so the upper limits for REM and Oa are set at 0.20% and 0.010, respectively. %.

When V, Nb and Ti exceed 0.050%, they tend to form carbonitrides even at high temperatures, resulting in a hardness of 30%.
Hl((3), and the quenching hardness becomes unstable, so the upper limit of these elements was set to 0.050% or less.

In this invention, in addition to the seven main components explained above, the following unavoidable components are allowed.

S1≦0.7% Sl is an element that generates ferrite at the material temperature, and addition of more than 0.7% of Si not only reduces the total quenching hardness but also has a negative impact on toughness. The limit is set to 0.7%, and the less (4') the better.

Ni and Qu≦0.7% Ni and Qu are elements that stabilize the quenching hardness in quenching from high temperatures in the same way as Mn, but in this invention, Mn is contained at 0.5 to 2.5%. Is that purpose achieved by letting? 4, so especially Ni,
There is no need to add Ou. However, about 0.05 to 0.7% of Ni and O are mixed in from the scrap used in the steelmaking process, and the existence of this amount of Ni does not disrupt the above balance and does not cause problems with separate installation. If it exceeds 0.7%, hot workability at high temperatures will be impaired and the yield in the manufacturing process of steel sheets will be significantly lowered, so an upper limit of 0.7% is allowed for each.

Further, as the main element mixed as an impurity, it is preferable to reduce P as much as possible from the viewpoint of toughness, and it is also desirable to reduce S from the viewpoint of resistance to induction.

Note that since oxygen is harmful to toughness and induction resistance, it is preferable to use oxygen to deoxidize until the AN in the steel is 0.05% or less.

In this invention, martenzite yarn stainless steel with the above-mentioned composition is melted, hot-rolled by a conventional method, then punched and subjected to necessary grinding to finish it into a motorcycle disc brake. Hardness of 30 to 40 HRG can be easily obtained only by quenching from a wide temperature range of about At the same time, it can have extremely excellent toughness.

Examples of this invention will be described below.

50Icfl of each component steel of Al-flat j2 shown in Table 1
A hot-rolled annealed plate with a thickness of 6+Nm was prepared by melting in a small high-frequency melting furnace, hot rolling and annealing under known conditions, and then holding the plate in a temperature range of 850° to 1100°C for 5 minutes before oiling. Quenching was performed and the relationship between quenching temperature, hardness, toughness, and corrosion resistance was investigated. The sample material is A I = A
8 is a steel according to the present invention, and 9 to A 12 are comparative steels.

The relationship between Rockwell hardness and quenching temperature is shown in Table 2.The temperature range for obtaining a quenching hardness of 30 to 440 HRG is extremely narrow for comparison steels, except for A9 low 0 # and In steels. On the other hand, in this invention, the temperature itself can be determined! It is clear that the range is extremely wide, from J00° to 1]00°C.

Table 3 shows the relationship between the ductility-brittle transition temperature and the quenching temperature in the Charpy impact test using JI No. 34% size test pieces.

＼ As is clear from Table 3, according to the present invention, even if the quenching hardness is 80 to 4. The transition temperature is below room temperature.

Of course, the induction resistance of the steel according to the present invention is also very good, and none of the steels uttered in the salt spray test (JIS Z2a7]).

As is clear from the example in the above ml, this invention is applicable to low carbon martenite stainless steel, the sum of C and N as its chemical components +ii: f 0 , 0
4 to 0.10%, especially Mn total 0.5 to 2.
By limiting the heat treatment to 5%, it is possible to stabilize the hardness of 30 = 4・OHRe by simply quenching from a wide rib temperature of 900° to 1100° without requiring strict heat treatment control. Furthermore, B is added or in addition, trace amounts of REM, Oa, Nb, V and Ti are added.
By adding one or more of these, the toughness during quenching can be significantly improved, and in this way, it is possible to provide a particularly safe brake Φ function when used in motorcycle brake discs.

Claims (1)

[Claims] 1. From 0.04% by weight in total amount to o, ]Ovl[amount%
(0+N)'t, 0.5~2.5'iJ7
fi1% Mn and 10.0-14.5 g'i ke%
(7) Qr and 0.0005-0.010 heavy child type OB
The remainder is unavoidable contaminants and Fe.
It has a composition of f!, and has a sufficiently low ductility-brittle transition temperature even after quenching. c A low carbon martenzite stainless steel heat-abrasive plate material with excellent toughness for motorcycle disc brakes. (C + N), which is 0.04% by weight to 0010% by weight in total - 1 standard, is combined with 0.5 to 2.5% by weight of In and 10% by weight.
．． 0 to 14.5 heavy bean paste-% Or and O', 0005 to
Contains 0.010 wt. 111% B, and 0.20
η (contains at least one selected from REM in an amount of % or less, Ca in an amount not more than 0.010% by weight, and V, Nb, and Ti in an amount not more than 0.050% by weight each, the remainder being unavoidable contaminants and A low-carbon martensitic stainless steel hot-rolled sheet with excellent toughness for use in motorcycle disc brakes, which has a composition of Fe and has a sufficiently low ductility-brittle transition temperature even after quenching.