A method for controlling carbide network in a bearing steel wire rod by controlling cooling and controlling rolling

Abstract

A method for controlling carbide network in a bearing steel wire rod by controlling cooling and rolling, comprises the following steps: rapidly rolling a bar to a wire rod and spinning it into a loose coil, controlling the rolling temperature at 780° C.-880° C.; and the spinning temperature at 750° C.-850° C.; carrying out on-line controlling cooling of continuous loose coils using EDC water bath austempering cooling process, controlling the cooling rate at 2.0° C./s-10° C./s, and controlling the final cooling temperature within 620-630° C.; after EDC water bath austempering cooling, using slow cooling under a cover, and the temperature is controlled to be 400° C.-500° C. when being removed out of the cover; after slow cooling, collecting coils, and cooling in air to the room temperature.

Claims

1. A method for controlling carbide network in a bearing steel wire rod by controlling cooling and controlling rolling, characterized in comprising rapidly rolling a bar to a wire with a specified specification and spinning it into a loose coil, controlling the rolling temperature at 780° C.-880° C.; and controlling the spinning temperature at 750° C.-850° C.; on-line controlling cooling of continuous loose coils using EDC water bath austempering cooling process, controlling the cooling rate at 2.0° C./s-10° C./s, and controlling the final cooling temperature within 620-630° C.; after EDC water bath austempering cooling, slow cooling under a cover, and the temperature is controlled to be 400° C.-500° C. when being removed out of the cover; after slow cooling, collecting coils, and cooling in air to a room temperature.

2. The method for controlling carbide network in a bearing steel wire rod by controlling cooling and controlling rolling according to claim 1, which is characterized in that the rolling speed is controlled to be 8.4 m/s-34.0 m/s.

3. The method for controlling carbide network in a bearing steel wire rod by controlling cooling and controlling rolling according to claim 1, which is characterized in that the water cooling rate of EDC water bath austempering cooling is 4.0° C./s-9° C./s.

4. The method for controlling carbide network in a bearing steel wire rod by controlling and controlling rolling according to claim 3, which is characterized in that the temperature of EDC water bath austempering cooling is 90° C.-100° C., so as to stabilize the water cooling rate.

5. The method for controlling carbide network in a bearing steel wire rod by controlling cooling and controlling rolling according to claim 1, which is characterized in that: according to wire rods of different specifications, the water bath cooling time is controlled to 20-80 s as to match the cooling rate, wherein the cooling rate is relatively lower when the wire rod has a larger diameter, and the corresponding water bath cooling time is longer.

6. The method for controlling carbide network in a bearing steel wire rod by controlling cooling and controlling rolling according to claim 1, which is characterized in that after spinning, the wire rods are treated with controlling cooling by using EDC water bath austempering; and after being removed out of the water, the temperature difference between that at the midpoint and that at the lap point in the wire rod is ≤10° C.; the midpoint refers to the most front end of the coil; the lap point is a contact point at two ends of two coils, when a coil is bent over another coil.

7. The method for controlling carbide network in a bearing steel wire rod by controlling cooling and controlling rolling according to claim 1, which is characterized in that: after the wire rod is rolled into a reducing & sizing mill, the temperature in the reducing & sizing mill is the final rolling temperature of the wire rod.

8. The method for controlling carbide network in a bearing steel wire rod by controlling cooling and controlling rolling according to claim 1, which is characterized in that: the method is applicable in producing Φ12 mm-25 mm high-carbon-chromium bearing steel wire rod.

9. The method for controlling carbide network in a bearing steel wire rod by controlling cooling and controlling rolling according to claim 8, which is characterized in that: the bearing steel wire rod contains the following chemical constituents by mass percentage: C 0.95-1.05%, Si 0.15-0.35%, Mn 0.25-0.45% , Cr 1.30-1.65%, Mo≤0.10%, Ni≤0.25%, Al≤0.050%, P≤0.025% , S≤0.020%, Cu≤0.25%, Ca≤0.0010%, O≤0.0012%, Ti≤0.0050%, As≤0.040%, Pb≤0.002%, As+Sn+Sb≤0.075%, the balance is Fe and any unavoidable impurities.

10. An application of a method for controlling carbide network in a bearing steel wire rod by controlling cooling and controlling rolling according to claim 1, which is characterized in that: the method is applicable in producing high-carbon-chromium bearing steel wire rod with a carbide network level ≤2.5.

Description

DESCRIPTION OF THE ATTACHED DRAWINGS

[0028] FIG. 1 depicts a schematic diagram of a carbide network form in the wire rod according to Embodiment 1 of the present invention;

[0029] FIG. 2 depicts a schematic diagram of a carbide network form in the wire rod according to Embodiment 2 of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0030] In combination with optimal embodiments of the present invention, the method of controlling carbide network in Φ12 mm-25 mm high-carbon-chromium bearing steel wire rod using controlling cooling and controlling rolling is illustrated in detailed below. However, the embodiment is only a description of an optimal embodiment of the present invention, and does not constitute any limitation on the scope of the invention.

Embodiment 1

[0031] Φ18 mm high-carbon-chromium bearing steel wire rods are rolled to the specified size by high speed wire rolling, and fabricated into loose coils by spinning. The carbide network is controlled according to the following technological parameters: the temperature in the reducing & sizing mill (i.e. The final rolling temperature) is 830° C.-870° C., the spinning temperature of wire rods is 810° C.-850° C.; when conducting on-line controlling cooling on wire rods by EDC water bath austempering cooling after spinning, the water bath temperature is 90° C.-97° C., the water bath cooling time is 20 s-80 s; the polishing temperature of wire rods after EDC water bath cooling is 620° C.-630° C. After the wire rod are polished, slow cooling under a cover is used, the holding time is 30 min-60 min, and the temperature after slow cooling is 430-470 ° C. After being removed out of the cover, the coils are cooled in air to the room temperature.

[0032] Chemical constituents of the product include: C 1.0%, Si 0.32%, Mn 0.30%, Cr 1.44%, Mo 0.01%, Ni 0.02%, Al 0.014%, P 0.014%, S 0.002%, Cu 0.08%, Ca 0.0002%, O 0.0008%, Ti 0.0010%, As 0.005%, Pb 0.001%, As+Sn+Sb≤0.011%, the balance is Fe and any unavoidable impurities.

[0033] A product sample is taken to evaluate the level of a carbide network, and the carbide network level of the sample is as shown in Table 1.

Embodiment 2

[0034] Φ13.5 mm high-carbon-chromium bearing steel wire rods are rolled to the specified size by high speed wire rolling, and subjected to spinning. The carbide network is controlled according to the following technological parameters: the temperature in the reducing & sizing mill is 800° C.-850° C., the spinning temperature of wire rods is 800° C.-840° C.; after spinning and on-line EDC water bath austempering cooling on wire rods, the water bath temperature is 90° C.-97° C., the water bath cooling time is 20 s-60 s; the polishing temperature of wire rods after EDC water bath cooling is 620° C.-630° C. After the wire rods are polished, slow cooling under a cover is used, the holding time is 40 min-60 min, and the temperature after slow cooling is 420-450 ° C. After being removed out of the cover, the coils are cooled in air to the room temperature.

[0035] Chemical constituents of the product include: C 0.98%, Si 0.29%, Mn 0.31%, Cr 1.45%, Mo 0.01%, Ni 0.02%, Al 0.025%, P 0.012%, S 0.001%, Cu 0.09%, Ca 0.0001%, O 0.0006%, Ti 0.0006%, As 0.0013%, Pb 0.001%, As+Sn+Sb<0.009%, the balance is Fe and any unavoidable impurities.

[0036] A product sample is taken to evaluate the level of a carbide network, and the carbide network level of the sample is as shown in Table 1.

TABLE-US-00001 TABLE 1 Test results of carbide networks sampled according to Embodiments 1 and 2 Carbide Test Test Test Test Test network sample sample sample sample sample level 1 2 3 4 5 Embodiment 1 1.5 1.5 1.5 1.5 1.5 Embodiment 2 1.5 1.5 1.5 1.5 1.5

[0037] As shown in Table 1, EDC water bath austempering +slow cooling under a cover is used for controlling cooling of the coils, which effectively inhibits precipitation of carbide in the cooling process, so that a non-equilibrium microstructure is obtained to form short-strip or hemispherical carbides, thereby finally controlling the carbide network.

[0038] In addition to the above embodiments, the invention also has other embodiments, and any technical scheme formed by equivalent transformation or equivalent substitution should fall within the scope of protection scope of the claims of the present invention.