Low cost lean production bainitic steel wheel for rail transit, and manufacturing method therefor

Abstract

The present invention discloses a low cost lean production bainitic steel wheel for rail transit and a manufacturing method therefor. The steel wheel contains elements with the following weight percentages: carbon C: 0.15-0.45%, silicon Si: 1.00-2.50%, manganese Mn: 1.20-3.00%, rare earth RE: 0.001-0.040%, phosphorus P≤0.020%, and sulphur S≤0.020%, where the remaining is iron and unavoidable residual elements, and 3.00%≤Si+Mn≤5.00%. Compared with the prior art, through alloying design and a preparation process, 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 granular bainite, a supersaturated ferritic structure, and a small amount of pearlite. The wheel has high comprehensive mechanical properties and service performance. In addition, the heat treatment process and technology are fully used without particularly adding alloying elements such as Mo, Ni, V, Cr, and B, to greatly reduce costs of steel and realize lean production.

Claims

1. A manufacturing method for a bainitic steel wheel for rail transit, comprising smelting, molding, and heat treatment process, wherein the heat treatment process is: heating a molded wheel to austenite temperature, cooling a rim tread with a water spray to decrease a temperature of the wheel below 400° C., and performing tempering treatment, wherein performing the tempering treatment includes: performing tempering at a first 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, and wherein the bainitic steel wheel for rail transit consists of elements with the following weight percentages: carbon C: 0.15-0.45%, silicon Si: 1.00-2.50%, manganese Mn: 1.20-3.00%, rare earth RE: 0.001-0.040%, phosphorus P≤0.020%, and sulphur S≤0.020%, wherein the remaining is iron and unavoidable residual elements, and 3.00%≤Si+Mn≤5.00%.

2. The manufacturing method according to claim 1, wherein the heating of the molded wheel to the austenite temperature includes: heating to a second temperature in a range of 860-930° C. and maintaining at the second temperature for 2.0-2.5 hours.

3. The manufacturing method according to claim 1, wherein the heat treatment process can alternatively be: heating treatment of the wheel with waste heat after the molding, and cooling a rim tread of a molded wheel with a water spray to a temperature below 400° C., and performing tempering treatment.

4. The manufacturing method according to claim 1, wherein the heat treatment process can alternatively be: air cooling the wheel to decrease a temperature of the wheel below 400° C. after the wheel is molded, and performing tempering treatment.

5. A manufacturing method for a bainitic steel wheel for rail transit, comprising smelting, molding, and heat treatment process, wherein the heat treatment process is: heating a molded wheel to austenite temperature, cooling a rim tread with a water spray to decrease a temperature of the wheel below 400° C., and performing tempering treatment, wherein the tempering treatment includes: performing tempering at a first 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, and wherein the bainitic steel wheel for rail transit consists of elements with the following weight percentages: carbon C: 0.19-0.28%, silicon Si: 1.40-1.90%, manganese Mn: 1.50-2.20%, rare earth RE: 0.020-0.040%, phosphorus P≤0.020%, and sulphur S≤0.020%, wherein the remaining is iron and unavoidable residual elements, and 3.00%≤Si+Mn≤5.00%.

6. The manufacturing method according to claim 5, wherein the heating of the molded wheel to the austenite temperature includes: heating to a second temperature in a range of 860-930° C. and maintaining at the second temperature for 2.0-2.5 hours.

7. The manufacturing method according to claim 5, wherein the heat treatment process can alternatively be: heating treatment of the wheel with waste heat after the molding, and cooling a rim tread of a molded wheel with a water spray to decrease a temperature of the wheel below 400° C., and performing tempering treatment.

8. The manufacturing method according to claim 5, wherein the heat treatment process can alternatively be: air cooling the wheel to decrease a temperature of the wheel below 400° C. after the wheel is molded, 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. 4a is a diagram of a 100× optical metallographic structure of a rim according to Embodiment 3;

(9) FIG. 4b is a diagram of a 500× optical metallographic structure of a rim according to Embodiment 3;

(10) FIG. 5 shows hardness comparison between cross sections of rims of a wheel according to Embodiment 2 and a CL60 wheel;

(11) FIG. 6 is a continuous cooling transformation curve (CCT curve) of steel according to Embodiment 2;

(12) FIG. 7 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

(13) FIG. 8 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

(14) Weight percentages of chemical components of a 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 after ingot cutting, heating and rolling, heat treatment, and finishing.

Embodiment 1

(15) A low cost lean production bainitic steel wheel for rail transit contains elements with the following weight percentages shown in Table 2.

(16) A manufacturing method for the low cost lean production bainitic steel wheel for rail transit includes the following steps:

(17) 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; intensively cooling a rim with a water spray to a temperature below 400° C., performing self-tempering by using waste heat, and cooling to room temperature after the tempering, without performing additional tempering treatment.

(18) As shown in FIG. 2a and FIG. 2b, a metallographic structure of a rim of the wheel prepared in this embodiment is mainly carbide-free bainite plus a small amount of ferritic. 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

(19) A low cost lean production bainitic steel wheel for rail transit contains elements with the following weight percentages shown in Table 2.

(20) A manufacturing method for the low cost lean production bainitic steel wheel for rail transit includes the following steps:

(21) forming the wheel by using liquid steel in Embodiment 2 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; cooling a rim with a water spray to a temperature below 400° C., performing self-tempering by using waste heat, and cooling to room temperature after the tempering, without performing additional tempering treatment.

(22) As shown in FIG. 3, 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. FIG. 3a, FIG. 3b, FIG. 3c, and FIG. 3d, and matching between strength and toughness of the wheel is superior to that of a CL60 wheel.

Embodiment 3

(23) A low cost lean production bainitic steel wheel for rail transit contains elements with the following weight percentages shown in Table 2.

(24) A manufacturing method for the low cost lean production bainitic steel wheel for rail transit includes the following steps:

(25) forming the wheel by using liquid steel in Embodiment 3 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 870-890° C. and maintaining at the temperature for 2.0-2.5 hours; cooling a rim tread with a water spray to a temperature below 400° C., performing self-tempering by using waste heat, and cooling to room temperature after the tempering, without performing additional tempering treatment.

(26) As shown in FIG. 4a and FIG. 4b, 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.

(27) 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 RE P S Embodiment 1 0.32 2.01 1.22 0.010 0.011 0.009 Embodiment 2 0.25 1.55 1.68 0.037 0.010 0.007 Embodiment 3 0.18 1.72 2.45 0.022 0.014 0.010 CL60 wheel 0.63 0.24 0.71 / 0.010 0.001 Chinese Patent 0.20 1.50 1.80 / / / CN100395366C UK Patent 0.22 0.5-3.0 0.5-2.5 / / / CN1059239C

(28) The foregoing are chemical components of the wheel, and the remaining is iron and unavoidable impurities.

(29) TABLE-US-00003 TABLE 3 Mechanical properties of rims of wheels in Embodiments 1, 2, and 3 and comparison examples Cross- Room section temper- Kq Embodiment Rp.sub.0.2 Rm A Z hard- ature MPa .Math. and example MPa MPa % % ness HB KU J m.sup.1/2 Embodiment 1 671 1102 16 40 332 51 83.3 Embodiment 2 612 976 16.5 42 301 60 91.2 Embodiment 3 621 1007 17 42 312 55 86.6 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 CN1059239C (−20° C.)