A high-carbon chromium bearing steel wire rod containing sulfur and a method for manufacturing the same

Abstract

The present application relates to a kind of high-carbon chromium bearing steel wire rod containing sulfur and its manufacturing method, belong to wire rod steel field.The chemical composition of wire rod is designed as C:0.95~1.05%, Si:0.15~0.40%, Mn:0.25~0.45%, P:≤0.015%, S:0.020~0.055%, Cr:1.35~1.65%, Al:0.030~0.060%, Cu≤0.10%, Mo≤0.05%, Ni≤0.05%, As+Sn+Sb≤0.015%, O≤0.0006%, Ti≤0.0015%, Ca≤0.001%, the balance is Fe and inevitable impurity element.The production process is: converter initial smelting-LF refining-vacuum degassing-continuous casting-hot delivery-heated casting blank+ breakdown rolling-intermediate billet surface treatment-intermediate billet heating+wire rod rolling-controlling cooling.The present application develops a kind of wire rod easy to turn or deep hole drilling processing, and the production method of the wire rod can save production cost greatly and improve production efficiency.

Description

Technical Field

[0001] This invention relates to a sulfur-containing high-carbon chromium bearing steel and its manufacturing method, belonging to the field of steel wire manufacturing. Background Technology

[0002] High-carbon chromium bearing steel accounts for more than 80% of all bearing steels. It has high hardness, good wear resistance, and high elastic limit. Therefore, it is widely used in transportation, machinery, machine tool equipment and other fields to manufacture rolling elements, rings, pins, valve bodies and other workpieces. The subsequent customer processing and forming processes mainly include: forging and cold heading for rolling elements and rings, while turning and deep hole drilling are mainly used for pins and valve bodies. Due to the different machining methods of steel, the performance requirements of the material are also different.

[0003] In bearing manufacturing processes, turning and deep hole drilling are increasingly common processes for producing precision, high-end valve bodies or pins and other unconventional products. However, ordinary high-carbon chromium bearing steel in China currently suffers from problems such as tool sticking and tool breakage, which affect machining accuracy and production efficiency.

[0004] Patent publication number CN102251197 A discloses a high-carbon chromium bearing steel and its manufacturing method. The production process involves producing billets using an electric furnace and die casting. This process has significant drawbacks, including high labor intensity, severe environmental pollution, and low yield, and is considered an obsolete technology. Furthermore, due to the use of scrap steel for smelting, residual elements cannot be guaranteed, affecting the fatigue performance of the final product. Additionally, the S content in this technology is relatively low (0.005-0.020%). Although this improves machinability, it can cause blockage of deep holes during fine drilling due to the generation of large chips.

[0005] Patent publication number CN102352466 A discloses a high-carbon chromium bearing GCr15 and its production method. This technology adds elements such as V, Ti, and N, and adds silicon barium wire during the smelting process. This technology is not only costly, but the addition of V, Ti, N and silicon barium wire will also increase the labor intensity of workers, which is not in line with the current low-cost and high-efficiency route. Moreover, the more elements added, the more detrimental it is to the control of steel purity. This technology does not use a special continuous casting process, and due to the addition of sulfur, it will inevitably increase the problem of sulfide core segregation, which will have an adverse effect on the fatigue life of the final product.

[0006] Patent publication number CN107747034 A discloses a high-carbon chromium bearing steel for railway freight car bearings and its preparation method. This technology mentions control methods for the purity, segregation and carbides of the steel. However, its strict control of sulfur content is not suitable for precision turning or deep hole drilling. At the same time, the invention does not involve the control of decarburization quality, which is not conducive to the overall fatigue life of the final product.

[0007] A search of relevant patent literature revealed few methods for producing sulfur-containing high-carbon chromium bearing steel, especially wire rod. Furthermore, the closest existing technologies mentioned above are all for bar products and do not involve existing technologies that specifically improve turning or deep hole drilling for wire rods. At the same time, there is a lack of low-cost sulfur-containing high-carbon chromium bearing steel and its manufacturing method that considers comprehensive properties such as segregation, purity, carbides, and decarburization.

[0008] In summary, to address the current issues of tool sticking, tool breakage, and long fatigue life encountered by customers in turning or deep hole drilling, reduce sulfide segregation, improve yield and production efficiency, and lower customer costs, it is necessary to propose a new low-cost, high-efficiency bearing steel and its production process that is economical, environmentally friendly, beneficial for subsequent processing, and has a long fatigue life. This has significant economic and social value. Summary of the Invention

[0009] The purpose of this invention is to provide a sulfur-containing high-carbon chromium bearing steel wire rod and its manufacturing method. The forming billet used for this wire rod is a continuously cast billet. The method overcomes the problems of severe central segregation of sulfides, high residual elements, poor purity, and inadequate carbide and decarburization in existing technologies during the continuous casting process. It provides customers with a hot-rolled wire rod production method that is easy to machine or deep-hole drill, and can significantly save production costs and improve production efficiency. Through optimized smelting and continuous casting processes, and reasonable heating and rolling processes, the obtained wire rod has excellent performance. The final wire rod microstructure meets the following requirements: inclusion level: central segregation ≤1.0; coarse A ≤0.5, fine A ≤1.0, coarse B ≤0.5, fine B ≤1.5, DS ≤0.5; carbide network ≤2.5 grade, banded structure ≤2.0 grade, decarburized layer thickness ≤0.05mm; grain size ≤8 grade. The microstructure is a pearlitic structure with a lamellar spacing of 0.12~0.15μm.

[0010] The technical solution adopted in this invention is: a sulfur-containing high-carbon chromium bearing steel and its manufacturing method. The chemical composition of the steel is designed by mass percentage as follows: C: 0.95-1.05%, Si: 0.15-0.40%, Mn: 0.25-0.45%, P: ≤0.015%, S: 0.020-0.055%, Cr: 1.35-1.65%, Al: 0.030-0.060%, Cu≤0.10%, Mo≤0.05%, Ni≤0.05%, As+Sn+Sb≤0.015%, O≤0.0006%, Ti≤0.0015%, Ca≤0.001%, with the balance being Fe and unavoidable impurity elements.

[0011] The design principle of the added elements in the high-carbon chromium bearing steel of this invention is as follows:

[0012] S: 0.020–0.055%. S is a free-machining element. When steel contains a certain amount of Mn, it easily forms MnS or MnS-containing complexes, thereby improving the turning or drilling performance of the material. However, if S is below 0.020%, the turning or drilling chips become significantly larger, which is not conducive to removal. Sulfides usually have low melting points. If the S content is too high, the material will form core segregation, resulting in hot brittleness and an increased tendency for decarburization. To fully utilize the effect, the S content range of the steel in this invention is set to 0.020–0.055%, more preferably 0.020–0.030%.

[0013] Al: 0.030–0.060%. Besides acting as a deoxidizer to reduce the oxygen content in steel, Al can also form aluminum nitride with nitrogen, refining grains and exhibiting strong solid solution strengthening, thus improving tempering stability. To control the residual austenite ratio in the final product and obtain better hardness and wear resistance, the Al content should be designed to be greater than 0.030%. However, since the deoxidation product Al2O3 is brittle, it breaks during forging and rolling, forming chain-like strips along the deformation direction, affecting fatigue performance. Furthermore, steel with high aluminum content has poorer surface quality in the cast billet. To ensure comprehensive performance, the Al content range for the steel in this invention is set to 0.030–0.060%, more preferably 0.035–0.045%.

[0014] Another objective of this invention is to provide a production process for sulfur-containing high-carbon chromium bearing steel, the specific process of which is as follows:

[0015] KR, converter primary refining — LF refining — (RH) vacuum degassing — continuous casting — hot delivery — heated billet + billet rolling — intermediate billet surface treatment — intermediate billet heating + rolling wire rod — controlled cooling — inspection — packaging and warehousing.

[0016] The specific steps are as follows:

[0017] (1) Smelting: The molten iron is successively processed through KR molten iron smelting, converter primary smelting, LF refining and (RH) vacuum degassing. The converter adopts the whole molten iron smelting process to control the carbon at the end point ≥0.15% and carry out preliminary alloying. In the initial stage of LF refining, two methods of precipitation and diffusion deoxidation are adopted: aluminum iron is added in the early stage for precipitation deoxidation, and aluminum particles and silicon carbide are mixed and dispersed on the slag surface for diffusion deoxidation. After the LF refining is completed, aluminum wire and sulfur wire are fed in sequence to ensure that large particles of sulfide and oxide are formed and floated during the vacuum degassing process, and to change the morphology of sulfide inclusions in the molten steel, so as to reduce the amount of harmful residual elements and obtain high purity steel.

[0018] (2) Continuous casting: Preferably, the tundish is selected to use the heating function to control the superheat of the pouring to 10-20℃, the crystallizer is equipped with electromagnetic stirring to accelerate the floating of inclusions and reduce the temperature difference of billet, the secondary cooling adopts atomized weak cooling, the electromagnetic stirring current at the end of solidification is >500A, and it is combined with dynamic light reduction, with a total reduction of ≥12mm, to obtain a continuous casting billet with good segregation quality and a size of 390mm*510mm or more.

[0019] (3) Heating of continuous casting billet: Preferably, the hot billet is directly transferred to a continuous walking furnace to achieve a hot charging temperature of ≥500℃, and is rapidly heated to 1180~1260℃ for holding. The heating rate is 100~200℃ / h, and the holding time is ≥9h, so that the carbides in the billet are diffused and evenly distributed, and the homogeneity of the material is improved.

[0020] (4) Initial rolling: The initial rolling temperature is set at ≥1000℃, the cumulative compression ratio of the first two rolling passes is ≥3, the continuous rolling temperature is ≥950℃, the final rolling temperature is ≥850℃, and the total compression ratio of the initial rolling is ≥4.8. High-pressure water descaling is used in the initial rolling process to obtain 140-200mm thick billets with excellent segregation quality, no pitting, cracks, or dents on the surface, and fine and dispersed carbide particles. 2 Intermediate billet.

[0021] (5) Surface treatment of intermediate billet: The intermediate billet is quickly removed from the line and slowly cooled to ≤150℃. The surface is finished and the peeling depth is ≥1.0mm to reduce the decarburization depth of the finished product and reduce surface defects.

[0022] (6) Intermediate billet heating: For cold billets, the heating rate is 750-850℃ / h when the billet temperature is ≤800℃; and 200-300℃ / h when the billet temperature is >800℃. The temperature is raised to the homogenization zone temperature of 980±30℃, and the holding time is 0.5-1h. After rapidly heating to cross the decarburization sensitive temperature, a short holding time is performed to reduce the depth of the surface decarburization layer.

[0023] (7) Controlled rolling of wire rod: The high-reduction rolling process is adopted. High-pressure water descaling is used before the initial rolling. The initial rolling temperature is set to ≥900℃, the initial rolling compression ratio is ≥1.2, the temperature of entering the intermediate rolling and pre-finishing rolling is ≥930℃, the temperature of entering the finishing rolling is 680~780℃, the two-phase zone rolling is carried out, the wire exiting temperature is 680~780℃, and the total compression ratio of the entire rolling process is ≥40.

[0024] (8) Controlled cooling of wire rod: After spinning, the wire rod is cooled by blowing air at a rate of 3-5℃ / s. After controlled cooling, the wire rod temperature is 550-680℃. It is then quickly placed into an insulation cover for slow cooling to ≤150℃ before being coiled off the production line to obtain wire rods with fine carbide particles, a small amount of pre-spheroidized cementite, and good cross-sectional homogeneity.

[0025] (9) Inspection: The offline wire rod is inspected for carbides, grain size, inclusions, and decarburization. If all are qualified, the finished product of hot-rolled wire rod of sulfur-containing high carbon chromium bearing steel is obtained.

[0026] The metallographic structure of the hot-rolled wire rod obtained by this invention is a fine lamellar pearlite structure. This pearlite structure is easy to spheroidize during subsequent heat treatment, and the uniformity of the structure is better after quenching and tempering, which provides a guarantee for the fatigue life of the final product.

[0027] The manufacturing method of sulfur-containing high-carbon chromium bearing steel wire rod of the present invention has the following characteristics:

[0028] 1) Sulfur and aluminum wires are fed in at the end of the refining process to deduct the S and Al losses during the RH process. This ensures that the Al and S composition meets the target range after the RH process is completed, and no further composition is added. This allows the large particles of Al2O3 and sulfide to float fully during the RH vacuum process, while the fine A and B type inclusions are evenly distributed in the molten steel, thus improving the cleanliness of the molten steel.

[0029] 2) During the continuous casting process, low superheat straightening, heavy pressure at the end of solidification, and high current electromagnetic stirring at the end are used to reduce core segregation and effectively improve billet segregation.

[0030] 3) The sulfur-containing high-carbon chromium bearing steel wire rod of the present invention is a high-carbon medium-sulfur hypereutectoid steel with strong sensitivity to surface decarburization and cracking. It is difficult to control the quality of surface defects. After continuous casting, it must be taken offline in time for controlled temperature and slow cooling. The cooling rate is 50-80℃ / h, the offline temperature is ≥550℃, and the billet temperature is ≤150℃. At the same time, the billet must be surface cleaned before entering the wire rod rolling furnace to ensure the decarburization and surface quality of the final wire rod product.

[0031] 4) In the controlled rolling of wire rod, the entry temperature to the finishing mill is 680–780℃, and the exit temperature is also 680–780℃. This ensures that the entire finishing mill temperature is within the two-phase rolling region, allowing the untransformed grains to elongate further and form more deformation bands within the grains. Furthermore, when the transformed grains are compressed, substructures form within the grains. During the cooling process after rolling, both undergo phase transformation to form a fine polygonal grain structure with a large tilt angle, ultimately obtaining a uniform pearlitic structure with a lamellar spacing of 0.12–0.15 μm. This facilitates shorter heat treatment time for customers and improves product homogeneity, thereby reducing customer production costs.

[0032] 5) In the process of controlled cooling of wire rod, the present invention rapidly cools and cuts the wire rod. After controlled cooling, the wire rod temperature is 550-680°C, which quickly crosses the network precipitation temperature to reduce the network precipitation of carbides.

[0033] 6) During the solidification process, as the sulfur content increases, the average size of sulfides and carbides increases, and longitudinal segregation increases. Sulfide also increases the total amount of sulfide inclusions in the steel, which easily forms sulfide agglomerates in the center of the billet, exacerbating carbide segregation in the center of the billet. Ultimately, this leads to severe segregation in the center of the steel and excessive shrinkage cavities. At the same time, due to its thermal sensitivity, high-carbon steel with sulfur content is prone to increasing the decarburization rate on the surface, forming surface defects.

[0034] This invention employs a special refining method that ensures the special chemical composition of high-sulfur steel while improving the purity of the molten steel. In continuous casting, it uses low superheat, high reduction, electromagnetic stirring, and a weak cooling process to ensure excellent core segregation structure. High-temperature diffusion and a first-pass high-compression-ratio rolling are used to achieve dispersion and refinement of sulfides and carbides in the core. Furthermore, high-temperature billet rolling avoids the brittle temperature of sulfides. At the same time, low-temperature controlled rolling technology is used in wire rod rolling to effectively control surface quality and internal structure. This invention adopts a full-process product quality control technology, and the final product meets the customer's requirements for special processing performance and ultra-long service life.

[0035] The sulfur-containing high-carbon chromium bearing steel wire rod designed and produced by this invention has a simple composition, high purity, low carbide level, shallow decarburization, good material homogeneity, low production cost, and high production efficiency. Compared with mold casting production, it significantly improves the yield, improves the environment, meets the special processing needs of customers, and can achieve an ultra-long service life, increasing customer adhesion. Attached Figure Description

[0036] Figure 1 This is a 200x magnified metallographic image of the sulfide inclusions in the core of the material in an embodiment of the present invention.

[0037] Figure 2 This is a 2000x magnification metallographic image of the fine lamellar pearlite in an embodiment of the present invention.

[0038] Figure 3 This is a metallographic image with a grain size of 200x in an embodiment of the present invention. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to the accompanying drawings. The embodiments described are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0040] Implementation Cases 1-2

[0041] The sulfur-containing high-carbon chromium bearing steel of this invention is manufactured according to the following procedure:

[0042] 1) Smelting: After smelting in a 100-ton steelmaking furnace converter, the steel is refined outside the furnace. The molten steel is then degassed by RH vacuum treatment, and the mass percentage of each chemical element is strictly controlled according to requirements.

[0043] 2) Continuous casting: Molten steel is continuously cast into 390mm × 510mm square billets, with the superheat in the tundish controlled at 10–20℃. To control material segregation, advanced end-stage electromagnetic stirring is used during continuous casting, with an electromagnetic stirring current of 600A, a total light reduction of 16mm, and weak cooling in the secondary cooling zone. The percentage of chemical composition of the resulting continuously cast billets is shown in Table 1 below.

[0044] Table 1. (wt.%), balance is Fe and other unavoidable impurity elements.

[0045] Furnace number C Si Mn P S Cr Al 21014493 1.0 0.30 0.35 0.013 0.023 1.44 0.037 21014494 0.99 0.31 0.34 0.015 0.024 1.46 0.041 Furnace number Cu Mo Ni As+Sn+Sb O (ppm) Ti (ppm) Ca (ppm) 21014493 0.03 0.012 0.04 0.0081 4.7 11 2 21014494 0.02 0.015 0.05 0.0091 4.9 9 3

[0046] 3) Billet Heating + Billet Opening: The billet, heated to ≥500℃, is fed into a walking beam furnace for heating. After 4 hours, the temperature is raised to 1180~1260℃ for homogenization and holding for ≥9 hours. The initial rolling temperature is ≥1000℃, and the final rolling temperature is ≥850℃. The billet is rolled to a thickness of 150mm. 2 The intermediate blank.

[0047] The main specific process parameters in the above embodiments are shown in Table 2 below:

[0048] Table 2. (Main specific process parameters for billet heating and hot rolling)

[0049]

[0050] 4) Intermediate billet heating + rolled wire rod + controlled cooling of wire rod: After cleaning the surface of the intermediate billet to a depth of 2.0 mm, it is cold-charged into the furnace and rapidly heated to 800℃ in 1 hour, then heated again to the soaking zone temperature of 980±30℃ in 0.5 hours, and held at that temperature for 0.5 to 1 hour. The initial rolling temperature is set to ≥900℃, the intermediate rolling temperature to ≥930℃, the finishing rolling temperature to 680~780℃, and the wire drawing temperature to 680~780℃. After wire drawing, the wire rod is rapidly air-cooled to 550~680℃, and then slowly cooled to ≤150℃ in an insulation hood before being removed from the production line. The main specific process parameters in the above embodiments are shown in Table 3 below:

[0051] Table 3. (Main specific process parameters for intermediate billet heating and hot rolling)

[0052]

[0053] The sulfur-containing high-carbon chromium bearing steel wire rods from Examples 1 and 2 underwent relevant tests, and the purity, grain size, carbides, and core segregation were measured, as shown in Table 4 below:

[0054] Table 4 (Finished wire rod purity, grain size, carbide and segregation results)

[0055] Furnace number A thick A fine B (rough) B Fine DS Grain size net ribbon Decarbonization Central segregation 21014493 0.5 0.5 0.5 1.0 0.5 Level 8 2.0 1.0 0.04mm 1.0 21014494 0.5 0.5 0.5 1.0 0.5 Level 8 2.0 1.0 0.05mm 1.0

[0056] As can be seen from Table 4, the inclusions, grain size, carbides, and central segregation in the examples meet the design requirements, indicating that the material has very high cleanliness, fine grains, excellent carbides and homogeneity, and good machining or deep hole drilling performance due to the appropriate addition of S element.

[0057] The sulfur-containing high-carbon chromium bearing steel wire rod produced by the above process has a higher yield, improved environmental quality, and significantly reduced production costs compared to die casting. It also has better overall fatigue performance, which is beneficial for customers' subsequent processing and reduces their production costs.

Claims

1. A manufacturing method of a high carbon chromium bearing steel containing sulfur rod, characterized in that the chemical composition of the rod is designed as follows in percentage by mass: C: 0.95-1.05%, Si: 0.15-0.40%, Mn: 0.25-0.45%, P: ≤0.015%, S: 0.020-0.055%, Cr: 1.35-1.65%, Al: 0.030-0.060%, Cu≤0.10%, Mo≤0.05%, Ni≤0.05%, As+Sn+Sb≤0.015%, O≤0.0006%, Ti≤0.0015%, Ca≤0.001%, the balance being Fe and unavoidable impurities; The production steps of the wire rod include, Steel smelting: including KR hot metal smelting, converter smelting, LF refining and vacuum degassing, the converter smelting adopts a full hot metal smelting process, and the end-point carbon is controlled to be greater than or equal to 0.15%; in the initial stage of the LF refining, two ways of precipitation and diffusion deoxidation are adopted: aluminum-iron is added for precipitation deoxidation, and aluminum particles and silicon carbide are mixed and then dispersedly added to the slag surface for diffusion deoxidation; after the LF refining, aluminum wire and sulfur wire are fed in sequence, so that large particle sulfide and oxide inclusions float up in the vacuum degassing process and the sulfide inclusion morphology in the molten steel is changed; Continuous casting: the molten steel is cast into a continuous casting billet by using a continuous casting process; Continuous casting billet heating: the continuous casting billet is heated to make the structure completely austenitic, and the carbides in the billet are uniformly distributed by diffusion; Breakdown rolling: the breakdown rolling temperature is set to be greater than or equal to 1000℃, the cumulative compression ratio of the first rolling is greater than or equal to 3, the entry continuous rolling temperature is greater than or equal to 950℃, the final rolling temperature is greater than or equal to 850℃, the total compression ratio of the breakdown rolling is greater than or equal to 4.8, and high-pressure water descaling is adopted in the breakdown rolling process; Intermediate billet surface treatment: the intermediate billet is cooled to less than or equal to 150℃ by stacking and slow cooling, and the surface finishing peeling depth is greater than or equal to 1.0mm; Intermediate billet heating: the cold billet is heated, the heating speed is 750-850℃ / h when the billet temperature is less than or equal to 800℃, the heating speed is 200-300℃ / h when the billet temperature is greater than 800℃, the temperature is raised to the soaking section temperature 980±30℃, and the soaking time is 0.5-1h; Wire rod controlled rolling: a large reduction rolling process is adopted, high-pressure water descaling is adopted before the first rolling, the breakdown rolling temperature is set to be greater than or equal to 900℃, the first rolling compression ratio is greater than or equal to 1.2, the entry intermediate rolling and pre-precision rolling temperature is greater than or equal to 930℃, the entry precision rolling temperature is 680-780℃, the precision rolling is in the two-phase region, and the wire rod temperature is 680-780℃; Wire rod controlled cooling: the wire rod is air-cooled after wire drawing, the cooling speed is 3-5℃ / s, the wire rod temperature is 550-680℃ after air-cooled control, then the wire rod is cooled to less than or equal to 150℃ in a holding cover, and the wire rod with small carbide particles and a small amount of pre-spheroidized cementite is obtained by stacking and slow cooling.

2. The process for manufacturing of sulphur high carbon chromium bearing steel wire rod as claimed in claim 1 wherein: The content of sulfur in the wire rod is 0.020-0.030%.

3. The process for manufacturing of sulphur high carbon chromium bearing steel wire rod as claimed in claim 1 wherein: The content of aluminum in the wire rod is 0.035-0.045%.

4. The process for manufacturing of sulphur containing high carbon chromium bearing steel wire rod as claimed in claim 1 wherein: The inclusion level of the wire rod satisfies: center segregation≤1.0; A coarse≤0.5, A fine≤1.0, B coarse≤0.5, B fine≤1.5, DS≤0.5; carbide network≤2.5 level, banded structure≤2.0 level, and decarburization layer thickness≤0.05mm.

5. The process for manufacturing sulphur containing high carbon chromium bearing steel wire rod as claimed in claim 1 wherein: The structure of the wire rod is pearlite structure with a lamellar spacing of 0.12-0.15μm, and the grain size is≤8 level.

6. The process for manufacturing sulphur containing high carbon chromium bearing steel wire rod as claimed in claim 1 wherein: In the continuous casting step, the tundish is heated, the superheat of the molten steel is controlled to be 10-20°C, the crystallizer is equipped with electromagnetic stirring, the secondary cooling zone of the continuous casting is cooled by atomization, the end of solidification is subjected to electromagnetic stirring by a current of >500A, and dynamic soft reduction is performed on the casting, the total reduction is ≥12mm, and a continuous casting billet with a size of ≥390mm*510mm is obtained.

7. The process for manufacturing sulphur containing high carbon chromium bearing steel wire rod as claimed in claim 1 wherein: In the continuous casting billet heating step, the hot billet is directly transported to a continuous walking beam furnace, the hot charging temperature is ≥500°C, rapid heating is performed to 1180-1260°C for heat preservation, the heating speed is 100-200°C / h, and the heat preservation time is ≥9h.

8. The process for manufacturing sulphur containing high carbon chromium bearing steel wire rod as claimed in claim 1 wherein: In the blooming step, the continuous casting billet is bloomed into an intermediate billet having a cross-sectional area of 140 to 200 mm 2 .

9. The process for manufacturing sulphur containing high carbon chromium bearing steel wire rod as claimed in claim 1 wherein: In the wire rod controlled rolling step, the total rolling compression ratio is ≥40.

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