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%, phosphorus0.020%, and sulphur0.020%, where the remaining is iron and unavoidable residual elements, 1.50%Si+Ni3.00%, and 1.50%Mn+Ni+Cu3.00%. 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 high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation, wherein the high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation contains elements with the following weight percentages: carbon C: 0.10-0.40%, silicon Si: 1.00-2.00%, manganese Mn: 1.00-2.50%, copper Cu: 0.20-1.00%, boron B: 0.0001-0.035%, nickel Ni: 0.10-1.00%, phosphorus P0.020%, and sulphur S0.020%, wherein the remaining is iron and unavoidable residual elements; and 1.50%Si+Ni3.00%, and 1.50%Mn+Ni+Cu3.00%.

2. The high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation according to claim 1, wherein the high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation contains elements with the following weight percentages: 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 P0.020%, and sulphur S0.020%, wherein the remaining is iron and residual elements, 1.50%Si+Ni3.00%, and 1.50%Mn+Ni+Cu3.00%.

3. The high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation according to claim 2, wherein the high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation contains elements with the following weight percentages: 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%, wherein the remaining is iron and unavoidable residual elements.

4. The high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation according to claim 1, wherein a metallographic structure within 40 millimeters below a rim tread of the bainite steel wheel is a carbide-free bainite structure, namely, supersaturated lathy ferritic in nanometer scale, wherein film-shaped carbon-rich residual austenite in nanometer scale exists in the middle of the supersaturated lathy ferritic in nanometer scale, and a volume percent of the residual austenite is 4%-15%.

5. The high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation according to claim 1, wherein a rim microstructure of the wheel is a multiphase structure formed by supersaturated ferritic and carbon-rich residual austenite, and a size of the rim microstructure is in nanometer scale ranging from 1-999 nm.

6. A manufacturing method for the high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation according to claim 2, comprising smelting, refining, molding, and heat treatment processes, wherein the heat treatment process is: heating a molded wheel to austenite temperature, intensively cooling a rim tread with a water spray to a temperature below 400 C., and performing tempering treatment.

7. The manufacturing method for the high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation according to claim 6, wherein the heating to austenite temperature is specifically: heating to 860-930 C. and maintaining at the temperature for 2.0-2.5 hours.

8. The manufacturing method for the high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation according to claim 6, wherein the tempering treatment is: 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.

9. The manufacturing method for the high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation according to claim 6, wherein the heat treatment process can alternatively be: 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.

10. The manufacturing method for the high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation according to claim 6, wherein the heat treatment process can alternatively be: air cooling a wheel to a temperature below 400 C. after the wheel is molded, and performing tempering treatment.

11. The hi h strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation according to claim 2, wherein a metallographic structure within 40 millimeters below a rim tread of the bainite steel wheel is a carbide-free bainite structure, namely, supersaturated lathy ferritic in nanometer scale, wherein film-shaped carbon-rich residual austenite in nanometer scale exists in the middle of the supersaturated lathy ferritic in nanometer scale, and a volume percent of the residual austenite is 4%-15%.

12. The high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation according to claim 2, wherein a rim microstructure of the wheel is a multiphase structure formed by supersaturated ferritic and carbon-rich residual austenite, and a size of the rim microstructure is in nanometer scale ranging from 1-999 nm.

13. The manufacturing method for the high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation according to claim 7, wherein the tempering treatment is: 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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] 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;

[0057] FIG. 2a is a diagram of a 100 optical metallographic structure of a rim according to Embodiment 1;

[0058] FIG. 2b is a diagram of a 500 optical metallographic structure of a rim according to Embodiment 1;

[0059] FIG. 3a is a diagram of a 100 optical metallographic structure of a rim according to Embodiment 2;

[0060] FIG. 3b is a diagram of a 500 optical metallographic structure of a rim according to Embodiment 2;

[0061] FIG. 3c is a diagram of a 500 dyed metallographic structure of a rim according to Embodiment 2;

[0062] FIG. 3d is a diagram of a transmission electron microscope structure of a rim according to Embodiment 2;

[0063] FIG. 4 is a continuous cooling transformation curve (CCT curve) of steel according to Embodiment 2;

[0064] FIG. 5a is a diagram of a 100 optical metallographic structure of a rim according to Embodiment 3;

[0065] FIG. 5b is a diagram of a 500 optical metallographic structure of a rim according to Embodiment 3;

[0066] 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

[0067] 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

[0068] 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

[0069] 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.

[0070] A manufacturing method for the high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation includes the following steps:

[0071] 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.

[0072] 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

[0073] 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.

[0074] A manufacturing method for the high strength, high toughness, heat-cracking resistant bainite steel wheel for rail transportation includes the following steps:

[0075] 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.

[0076] 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

[0077] 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.

[0078] 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.

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 / / / / /

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