High strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation and manufacturing method thereof

Abstract

The present invention provides a high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation and a manufacturing method thereof. Components are: carbon 0.10-0.40%, silicon 1.00-2.00%, manganese 1.00-2.50%, copper 0.20-1.00%, boron 0.0001-0.035%, nickel 0.10-1.00%, phosphorus ≤0.020%, and sulphur ≤0.020%, where the remaining is iron and unavoidable residual elements, 1.50%≤Si+Ni≤3.00%, and 1.50%≤Mn+Ni+Cu≤3.00%. Compared with the prior art, in the present invention, by using design of the chemical compositions of steel and wheel manufacturing processes, especially a heat treatment process and technology, a rim of the wheel obtains a carbide-free bainite structure, and a web and a wheel hub obtain a metallographic structure based on granular bainite and a supersaturated ferritic structure. The wheel has comprehensive mechanical properties such as high strength, high toughness, heat-cracking resistant performance and good service performance, thereby improving a service life and comprehensive efficiency of the wheel, bringing specific economic and social benefits.

Claims

1. A bainite steel wheel for rail transportation, comprising: carbon C: 0.15-0.25%; silicon Si: 1.40-1.80; manganese Mn: 1.40-2.00%; copper Cu: 0.20-0.80%; boron B: 0.0003-0.005%; nickel Ni: 0.10-0.60%; phosphorus P≤0.020%; and sulphur S≤0.020%; wherein the remaining is iron and unavoidable residual elements; wherein 1.50%≤Si+Ni≤3.00%, and 1.50%≤Mn+Ni+Cu≤3.00%; wherein the portion of the bainite steel wheel that is between the surface of a rim tread and 40 millimeters below the rim tread is organized into a microstructure of a carbide-free bainite structure, wherein the carbide-free bainite structure comprises a supersaturated lath ferrite in nanometer scale, wherein a film-shaped carbon-rich residual austenite in nanometer scale is interspersed among the supersaturated lath ferrite, and wherein a volume percentage of the residual austenite is 4%-15%; and wherein the microstructure of the bainite steel wheel was formed by the steps of smelting, refining, molding, and heat treatment processes, wherein the heat treatment process comprises heating a molded wheel to austenite temperature by heating to 860-930° C. and maintaining at the temperature for 2.0-2.5 hours, intensively cooling a rim tread with a water spray to a temperature below 400° C., and performing tempering treatment.

2. The bainite steel wheel for rail transportation according to claim 1, comprising: carbon C: 0.18%; silicon Si: 1.63%; manganese Mn: 1.95%; copper Cu: 0.21%; boron B: 0.001%; nickel Ni: 0.18%; phosphorus P: 0.012%; and sulphur S: 0.008%.

3. The bainite steel wheel for rail transportation according to claim 1, wherein the microstructure is a multiphase structure formed by the supersaturated lath ferrite and the carbon-rich residual austenite, and a size of the nanometer scale ranges from 1-999 nm.

4. The bainite steel wheel for rail transportation according to claim 1, wherein a tempering treatment is as follows: performing tempering at medium or low temperature for more than 30 minutes when the temperature of the wheel is less than 400° C., and air cooling the wheel to room temperature after the tempering; or intensively cooling the rim tread with the water spray to the temperature below 400° C., and air cooling to room temperature, during which self-tempering is performed by using waste heat.

5. The bainite steel wheel for rail transportation according to claim 1, wherein the heat treatment process comprises: heating treatment of the wheel with high-temperature waste heat after the molding, and directly intensively cooling a rim tread of a molded wheel with a water spray to a temperature below 400° C., and performing tempering treatment.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of names of parts of a wheel, where 1: wheel hub hole; 2: outer side face of a rim; 3: rim; 4: inner side face of the rim; 5: web; 6: wheel hub; and 7: tread;

(2) FIG. 2a is a diagram of a 100× optical metallographic structure of a rim according to Embodiment 1;

(3) FIG. 2b is a diagram of a 500× optical metallographic structure of a rim according to Embodiment 1;

(4) FIG. 3a is a diagram of a 100× optical metallographic structure of a rim according to Embodiment 2;

(5) FIG. 3b is a diagram of a 500× optical metallographic structure of a rim according to Embodiment 2;

(6) FIG. 3c is a diagram of a 500× dyed metallographic structure of a rim according to Embodiment 2;

(7) FIG. 3d is a diagram of a transmission electron microscope structure of a rim according to Embodiment 2;

(8) FIG. 4 is a continuous cooling transformation curve (CCT curve) of steel according to Embodiment 2;

(9) FIG. 5a is a diagram of a 100× optical metallographic structure of a rim according to Embodiment 3;

(10) FIG. 5b is a diagram of a 500× optical metallographic structure of a rim according to Embodiment 3;

(11) FIG. 6 shows a relationship comparison between a friction coefficient and the number of revolutions in a friction and wear test of a wheel according to Embodiment 2 and a CL60 wheel; and

(12) FIG. 7 shows structures of deformation layers on surfaces of samples of a wheel according to Embodiment 2 and a CL60 wheel after a friction and wear test.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(13) Weight percentages of chemical components of wheel steel in Embodiments 1, 2, and 3 are shown in Table 2. In Embodiments 1, 2, and 3, a (1:0380 mm round billet directly cast after EAF smelting, and LF+RH refining and vacuum degassing is used. Then, the round billet forms a freight car wheel having a diameter of 840 mm, a passenger car wheel having a diameter of 915 mm, or the like after ingot cutting, heating and rolling, heat treatment, and finishing.

Embodiment 1

(14) A high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation contains elements with the following weight percentages shown in Table 2.

(15) A manufacturing method for the high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation includes the following steps:

(16) forming the wheel by using liquid steel in Embodiment 1 with chemical components shown in Table 2 through an EAF steelmaking process, an LF refining process, an RH vacuum treatment process, a round billet continuous casting process, an ingot cutting and rolling process, a heat treatment process, processing, and a finished product detection process. The heat treatment process is: heating to 860-930° C. and maintaining at the temperature for 2.0-2.5 hours; controlling and cooling a rim tread with a water spray, performing tempering treatment at 220° C. for 4.5-5.0 hours, and cooling to room temperature.

(17) As shown in FIG. 2a and FIG. 2b, a metallographic structure of a rim of the wheel prepared in this embodiment is a carbide-free bainite structure. Mechanical properties of the wheel in this embodiment are shown in Table 3, and matching between strength and toughness of the wheel is superior to that of a CL60 wheel.

Embodiment 2

(18) A high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation contains elements with the following weight percentages shown in Table 2.

(19) A manufacturing method for the high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation includes the following steps:

(20) forming the wheel by using liquid steel in Embodiment 2 with chemical components shown in Table 2 through a steelmaking process, a refining process, a vacuum degassing process, a round billet continuous casting process, an ingot cutting process, a forging and rolling process, a heat treatment process, processing, and a finished product detection process. The heat treatment process is: heating to 860-930° C. and maintaining at the temperature for 2.0-2.5 hours; controlling and cooling a rim tread with a water spray, performing tempering treatment at 280° C. for 4.5-5.0 hours, and cooling to room temperature.

(21) As shown in FIG. 3a, FIG. 3b, FIG. 3c, and FIG. 3d, a metallographic structure of a rim of the wheel prepared in this embodiment is mainly carbide-free bainite. Mechanical properties of the wheel in this embodiment are shown in Table 3, and matching between strength and toughness of the wheel is superior to that of a CL60 wheel.

Embodiment 3

(22) A wheel was formed by using liquid steel in Embodiment 3 with chemical components shown in Table 2 through a steelmaking process, a refining process, a vacuum degassing process, a round billet continuous casting process, an ingot cutting process, a forging and rolling process, a heat treatment process, processing, and a finished product detection process. The heat treatment process is: heating to 860-930° C. and maintaining at the temperature for 2.0-2.5 hours; controlling and cooling a rim tread with a water spray, and performing tempering treatment at 320° C. for 4.5-5.0 hours.

(23) As shown in FIG. 5a and FIG. 5b, a metallographic structure of a rim of the wheel prepared in this embodiment is mainly carbide-free bainite. Mechanical properties of the wheel in this embodiment are shown in Table 3, and matching between strength and toughness of the wheel is superior to that of a CL60 wheel.

(24) TABLE-US-00002 TABLE 2 Chemical components (wt %) of wheels in Embodiments 1, 2, and 3 and comparison examples. Embodiment and example C Si Mn Cu B Ni P S Embodiment 1 0.25 1.50 1.29 0.35 0.020 0.29 0.009 0.007 Embodiment 2 0.18 1.63 1.95 0.21 0.001 0.18 0.012 0.008 Embodiment 3 0.31 1.28 1.56 0.32 0.010 0.53 0.015 0.011 CL60 wheel 0.63 0.24 0.71 / / / 0.010 0.001 Chinese Patent 0.2 1.5 1.8 0.1  / 0.2  / / CN100395366C UK Patent CN1059239C 0.22 0.5-3.0 0.5-2.5 / / / / /

(25) TABLE-US-00003 TABLE 3 Mechanical properties of rims of wheels in Embodiments 1, 2, and 3 and comparison examples Cross-section Room Embodiment and Rp.sub.0.2 Rm hardness temperature K.sub.Q example MPa MPa A % Z % HB KU J MPa .Math. m.sup.1/2 Embodiment 1 612 1003 17 39 309 83 90.6 Embodiment 2 668 1060 16 39 315 78 83.1 Embodiment 3 717 1159 15 38 339 61 70.2 CL60 wheel 630 994 15.5 39 290 25 56.3 Chinese Patent 779 1198 16 40 360 52 / CN100395366C UK Patent 730 1250 17 55 400 39 60(−20° C.) CN1059239C