A medium-carbon non-rounding steel and its manufacturing method

Abstract

This invention relates to a medium-carbon non-adjustable round steel and its manufacturing method. In the billet slow cooling process, the billet temperature upon entering the slow cooling pit is greater than or equal to 600℃, and the slow cooling time is greater than or equal to 24 hours. Before entering the heating furnace, the billet temperature is greater than or equal to 300℃. In the billet heating process, the secondary heating temperature is higher than the homogenization temperature. In the high-pressure water descaling process, the descaling pressure is 18±1MPa. In the process of peeling defective round steel with a grinding wheel, a φ180 twelve-head round steel peeling machine with a grinding wheel specification of φ500×100×203 is used to peel defective materials from magnetic flux leakage testing. The peeling diameter reduction is 0.6mm, and the peeling is performed once. This invention can reduce surface stress cracks in round steel, improve the initial pass rate of magnetic flux leakage testing, reduce the scrap rate of round steel, reduce the number of peeling operations, improve the efficiency of grinding wheel peeling, shorten the finishing cycle, and ensure the finished product delivery time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of alloy materials, more particularly, it relates to a medium-carbon non-rounding steel and a manufacturing method thereof. BACKGROUND

[0002] The medium-carbon non-rounding steel contains 0.36-0.40% of carbon, 0.50-0.65% of silicon, 1.30-1.55% of manganese, 0.013-0.020% of nitrogen, 0.04-0.055% of sulfur, and ≤0.02% of vanadium and ≤0.01% of titanium. The steel is based on medium-carbon manganese steel, and vanadium, titanium and nitrogen trace elements are added to make them dissolve in austenite during heating. The solid solubility of vanadium, titanium and nitrogen in austenite decreases with cooling. The trace elements vanadium, titanium and nitrogen are precipitated in the first-precipitated ferrite and pearlite in the form of fine carbide nitrides. The medium-carbon non-rounding steel is commonly used for hot forged parts (such as crankshafts, connecting rods, etc.).

[0003] The medium-carbon non-rounding steel is used for forged parts such as crankshafts and connecting rods, and the surface quality of the round steel is required to be high, and the surface defect depth of the round steel is required to be ≤0.2mm. However, due to unreasonable production process control, stress cracks are easily generated on the surface of the round steel, resulting in a leakage magnetic preliminary exploration qualified rate of less than 60%. For the defect material of the leakage magnetic preliminary exploration, finishing grinding wheel peeling is required to rescue. When the depth of the stress crack is serious, it will exceed 0.5mm. The peeling diameter reduction amount of the original grinding wheel peeling process can only reach 0.3mm each time, and the defect material with a defect depth of less than 0.5mm can be rescued only after two times of grinding wheel peeling. The peeling efficiency is low, the finishing cycle is long, the finishing delivery period of the product is affected, the defect material with a defect depth greater than 0.5mm can only be scrapped due to the fact that the grinding size cannot meet the size tolerance requirement, and the scrap rate reaches 12%, which affects the metal yield rate and increases the production cost. SUMMARY

[0004] In view of the defects in the prior art, the present application aims to provide a medium-carbon non-rounding steel and a manufacturing method thereof, which can reduce the stress cracks on the surface of the round steel, improve the leakage magnetic preliminary exploration qualified rate, reduce the peeling frequency of the round steel, improve the grinding wheel peeling efficiency, shorten the finishing cycle, and ensure the finishing delivery period of the product.

[0005] The above technical purpose of the present application is achieved by the following technical scheme:

[0006] A manufacturing method of a medium-carbon non-rounding steel, the steps are as follows:

[0007] In the steel billet slow cooling process, the billet enters the slow cooling pit at a temperature greater than or equal to 600℃, and the slow cooling time is greater than or equal to 24 hours. Before entering the heating furnace, the temperature of the steel billet is greater than or equal to 300℃.

[0008] In the billet heating process, the second heating temperature is higher than the soaking temperature;

[0009] In the high-pressure water descaling process, the descaling pressure is 18±1 MPa;

[0010] In the process of grinding the unqualified round steel, the φ180 twelve grinding head round steel peeling machine is used, the grinding wheel specification is φ500*100*203, the magnetic flux leakage inspection defect material is peeled, the peeling diameter reduction amount is 0.6mm, and the peeling frequency is 1 time.

[0011] In one of the embodiments, in the process of grinding the unqualified round steel, the number of grinding heads used is 10-12.

[0012] In one of the embodiments, in the process of grinding the unqualified round steel, the first to fourth grinding heads use 16# grinding wheel pieces, and the fifth to twelfth grinding heads use 24# grinding wheel pieces; the first to fourth grinding heads use 16# grinding wheel pieces, the 16# coarse-grained grinding wheel increases the grinding amount, the fifth to twelfth grinding heads use 24# grinding wheel pieces, and the 24# fine-grained grinding wheel ensures the surface quality.

[0013] In one of the embodiments, in the process of grinding the unqualified round steel, the grinding head speed is 1450rpm.

[0014] In one of the embodiments, in the process of grinding the unqualified round steel, the main transmission speed is 750±50 rpm.

[0015] In one of the embodiments, in the process of grinding the unqualified round steel, the grinding head current is 20-25A, and the current of the first and twelfth grinding heads is controlled at 18A.

[0016] In one of the embodiments, in the process of grinding the unqualified round steel, the twelve grinding heads are divided into three groups, the first to fourth grinding heads are a group with a pressure of 0.25MPa; the fifth to eighth grinding heads are a second group with a pressure of 0.2MPa; and the ninth to twelfth grinding heads are a third group with a pressure of 0.15MPa.

[0017] In one of the embodiments, in the billet heating process, the second heating temperature is 1200-1250℃, and the soaking temperature is 1150±20℃.

[0018] In one of the embodiments, in the rough rolling process, the cooling water flow is controlled at 110-130m³ / h.

[0019] A medium-carbon non-rounding steel is prepared by the above manufacturing method.

[0020] In summary, the present application has the following beneficial effects:

[0021] The present application reduces the surface stress cracks of round steel, improves the leakage magnetic preliminary exploration qualified rate, reduces the round steel rejection rate, reduces the round steel peeling frequency, improves the grinding wheel peeling efficiency, shortens the finishing cycle, and ensures the finishing delivery period of the product, and the present application can be popularized and applied in the same type production line of special steel. DETAILED DESCRIPTION

[0022] The present application will be described in detail below in combination with examples.

[0023] The present application provides a manufacturing method of medium-carbon non-rounding steel, comprising the following steps:

[0024] S1, slow cooling of the billet: the temperature of the billet entering the slow cooling pit is greater than or equal to 600℃, the slow cooling time is greater than or equal to 24 hours, and the temperature of the billet before entering the heating furnace is greater than or equal to 300℃; the slow cooling time is not less than 24 hours, which is beneficial to the stress release of the continuous casting billet, and the temperature of the billet before entering the heating furnace is greater than or equal to 300℃, which can prevent the billet from generating new thermal stress in the preheating section;

[0025] In the existing old process, the temperature of the billet entering the heating furnace is not clearly specified, and the temperature of the billet entering the heating furnace is lower than 300℃, the temperature of the billet entering the furnace is low, and the billet will generate new thermal stress in the preheating process in the heating furnace;

[0026] S2, the continuous casting billet (specification 320*425*9000) enters the walking beam furnace for heating, the second heating temperature is 1200-1250℃, and the soaking temperature is 1150±20℃, and the second heating temperature higher than the soaking temperature is beneficial to the uniformity of heating and reduces the generation of thermal stress;

[0027] In the existing old process, the second heating temperature and the soaking temperature are not controlled, and the second heating temperature is lower than the soaking temperature;

[0028] S3, the billet after completing heating is descaled by high-pressure water, the descaling pressure is 18±1MPa, and the stress cracks generated when the cooling water cools the surface of the billet during the descaling process are reduced;

[0029] In the existing old process, the descaling pressure of high-pressure water is controlled at 23MPa;

[0030] S4. The descaled steel billet is rough rolled by a two-roll reversible rolling mill (φ1100×2500) using a large reduction rolling process. The rolling process is repeated 11 times to obtain a rolled piece with a size of 205×205. During the rolling process, the cooling water flow rate is controlled at 110-130m³ / h to reduce stress cracks generated during the cooling process of the rolled piece.

[0031] In the existing old process, the flow rate of cooling water is controlled at 190-210 m³ / h. During the cooling process of the rolled workpiece, stress cracks are easily generated by the cooling water.

[0032] S5. After rough rolling, the workpiece is cut off by a hydraulic shearing head with a head length greater than or equal to 100mm and a tail length greater than or equal to 100mm to remove end defects of the workpiece.

[0033] S6. The rolled piece enters the intermediate rolling process. The six continuous rolling mills in the intermediate rolling mill are all arranged alternately in a horizontal and vertical configuration. The rolling mill consists of φ750×6, all of which are fifth-generation short-stress rolling mills. The rolling temperature is greater than or equal to 850℃, and round steel is obtained. The round steel specification is Φ110mm ≤ Φ220mm. The finished product dimensional tolerance is controlled according to the upper limit positive tolerance of the second group of national standards.

[0034] S7. After intermediate rolling, the round steel is cut into multiple length sections by No. 1 flying shear. The maximum shearing section of No. 1 flying shear is Φ142mm, the shearing temperature is greater than or equal to 850℃, Φ132mm < round steel specification ≤ Φ142mm, round steel specification ≤ Φ110mm, head length is greater than or equal to 100mm, tail length is greater than or equal to 100mm, and head and tail defects are removed.

[0035] S8. Round steel enters the finishing rolling process. The finishing rolling mill has four continuous rolling stands, all of which are arranged alternately in a horizontal and vertical configuration. The mill consists of φ550×4, all of which are fifth-generation short-stress mills. The rolling temperature is greater than or equal to 850℃. The round steel specification is Φ70mm ≤ Φ105mm. The finished product dimensional tolerance is controlled according to the upper limit positive tolerance of the second group of national standards.

[0036] S9. After precision rolling, the round steel is cut into multiple length sections by No. 2 flying shear. The maximum shearing section of No. 2 flying shear is Φ132mm and the shearing temperature is greater than or equal to 50℃. When the round steel specification is ≤φ132mm, the No. 2 flying shear is used for multiple length sectioning.

[0037] S10, Grouping: Group the flying shear multiple rulers;

[0038] S11. Three Φ1800mm metal saws (saw #1, mobile saw, and saw #2) are used to cut round steel into sections at a cutting temperature of 700-850℃.

[0039] S12. The fully sawn round steel bars are placed on a cooling bed for air cooling and straightening.

[0040] S13, Online chamfering;

[0041] S14. Bundling, weighing, and warehousing;

[0042] S15, straightened, flawed, with a magnetic leakage of 0.2mm, qualified round steel is bundled and put into storage;

[0043] S16. For substandard round steel, perform abrasive wheel peeling. Specifically, use a φ180 twelve-head round steel peeling machine with a φ500×100×203 grinding wheel to peel the defective material from magnetic flux leakage testing. The peeling diameter reduction is 0.6mm, and the peeling is performed once. A new peeling process is adopted.

[0044] (1) The number of grinding heads used is 10-12;

[0045] (2) Grinding wheel usage: Grinding heads #1-4 use #16 grinding wheels, grinding heads #5-12 use #24 grinding wheels; grinding heads #1-4 use #16 grinding wheels, #16 coarse grinding wheels increase grinding amount, grinding heads #5-12 use #24 grinding wheels, #24 fine grinding wheels ensure surface quality.

[0046] (3) The grinding head speed is 1450 rpm;

[0047] (4) The main drive speed is 750 rpm (±50 rpm), which will be adjusted according to the peeling quality and grinding amount.

[0048] (5) The grinding head current is 20-25A, of which the current of grinding heads #1 and #12 is controlled at 18A;

[0049] (6) Grinding head pressure: The 12 grinding heads are divided into three groups. Grinding heads 1-4# are in one group with a pressure of 0.25MPa; grinding heads 5-8# are in the second group with a pressure of 0.2MPa; grinding heads 9-12# are in the third group with a pressure of 0.15MPa.

[0050] The grinding head pressure can be adjusted between 0.1 and 0.30 MPa. A good grinding amount and surface quality can be obtained between 0.1 and 0.2 MPa. If the grinding head pressure exceeds 0.3 MPa, the grinding head will bounce up and down, significantly affecting surface quality, resulting in scratches (24# grit grinding head) and a roughness greater than Ra12.5 μm. If the grinding head pressure is less than 0.1 MPa, the pressure is insufficient to meet the grinding head's downward pressure, preventing normal production. During production, the pressure is kept constant and not adjusted. High pressure in the initial grinding stage ensures the grinding amount, while slightly lower pressure in the subsequent stage ensures surface quality.

[0051] The existing peeling process is as follows: 7-8 grinding heads are used; all grinding wheels are 24# grinding wheels; the grinding head speed is 800-1450 rpm; the main drive speed is 1000 rpm, which is adjusted according to the peeling quality; the grinding head current is below 20A and above 17A; the pressure of each grinding head is adjusted between 0.1-0.30 MPa, but there are no specific regulations for the pressure of each grinding head.

[0052] This invention improves the diameter reduction of round steel by increasing the number of grinding heads, rationally using grinding wheel grit, controlling grinding speed, grinding current, and the speed at which round steel passes through the steel profile. The diameter reduction is increased from 0.3mm to 0.6mm.

[0053] S17. Re-test the peeled and ground round steel bars. If the magnetic leakage is 0.2mm, the qualified round steel bars are bundled and put into storage.

[0054] This invention reduces surface stress cracks in round steel and improves the initial magnetic flux leakage test pass rate by adopting a series of process improvement measures, including controlling the temperature of the billet during slow cooling into the heating furnace, ensuring the secondary heating temperature of the heating furnace is higher than the homogenization temperature, reducing the pressure of high-pressure water descaling, and reducing the amount of cooling water for the rolls. During rolling, the finished product is controlled according to the national standard group two positive tolerances, increasing the allowance for grinding and peeling, and reducing the scrap rate of round steel. Simultaneously, the grinding wheel peeling process is optimized, including the grinding wheel grit size, grinding speed, grinding current, and the number of grinding wheels used, increasing the diameter reduction per peeling from 0.3mm to 0.6mm, and reducing the number of peeling operations from two to one, thus improving peeling efficiency, shortening the finishing cycle, and ensuring the finished product delivery time. This invention can be widely applied in similar production lines for special steel.

[0055] The technical solution of the present invention will be illustrated below through specific embodiments and comparative examples.

[0056] Taking the production of φ100mm round bars from medium carbon non-adjustable steel continuous casting billets as an example, 25 medium carbon non-adjustable round steel continuous casting billets are selected, with billet serial numbers numbered 1-25. The billets are 320mm×425mm×9000mm in size. The 25 medium carbon non-adjustable steel continuous casting billets with good surface quality are divided into 5 groups, with 5 billets in each group. The first group adopts the old process, while the second to fifth groups adopt the process of this invention. Comparative Example 1

[0057] The first batch of medium carbon non-heat-resistant steel continuous casting billets was placed in the pit for slow cooling at 620°C. After a slow cooling time of 96 hours, the billets were heated in the heating furnace at a temperature of 50°C.

[0058] The continuously cast billet enters a walking beam furnace for heating, where the secondary heating temperature is 1150℃ and the soaking temperature is 1160℃.

[0059] The heated continuous casting billet is subjected to high-pressure water descaling at a pressure of 23 MPa.

[0060] After descaling, the continuously cast billet is rolled by a two-roll reversible rolling mill (φ1100×2500) using a high-reduction rolling process, with 11 rolling passes. The billet size is 205×205, and the cooling water flow rate is controlled at 200m³ / h.

[0061] The rolled workpiece is cut off from the end defects of the rolled billet by a hydraulic shearing head with a cutting length of 100mm.

[0062] The rolled piece enters the intermediate rolling process. The six continuous rolling mills in the intermediate rolling mill are all arranged alternately in a horizontal and vertical configuration. The rolling mill consists of φ750×6 mills, all of which are fifth-generation short-stress rolling mills. The rolling temperature is 860℃, and the rolled piece size is Φ120mm.

[0063] The shearing section is Φ120mm, the shearing temperature is 860℃, the head length is 120mm, the tail length is 120mm, and the head and tail defects are removed.

[0064] The rolled piece enters the finishing rolling process. The finishing rolling mill consists of four continuous rolling mills arranged alternately in a horizontal and vertical configuration. The mills are composed of φ550×4, all of which are fifth-generation short-stress rolling mills. The rolling temperature is 850℃, the round steel specification is Φ100mm, and the finished product dimensional tolerance is controlled according to the second group of national standards.

[0065] The No. 2 flying shear has a cutting section of Φ100mm and a cutting temperature of 850℃. The No. 2 flying shear is divided into multiple length sections.

[0066] The flying shears are grouped together; the round steel is cut into sections by three Φ1800mm metal saws (saw #1, moving saw, and saw #2), with a sawing temperature of 700℃-850℃.

[0067] After being sawn, the round steel bars are placed on a cooling bed for air cooling and straightening; after beveling online, they are bundled, weighed, and put into storage.

[0068] The round steel bars were straightened and then subjected to flaw detection. The magnetic flux leakage was controlled within 0.2 mm. The initial pass rate of magnetic flux leakage detection is shown in Table 1.

[0069] Qualified round steel bars are bundled and stored; unqualified round steel bars are peeled using a grinding wheel peeling machine with a φ180 twelve-head grinding wheel (φ500*100*203). The peeling process involves magnetic flux leakage testing to detect defects, and uses an older peeling technique.

[0070] (1) The number of grinding heads used is 8;

[0071] (2) All grinding wheels used are #24 grinding wheels;

[0072] (3) The grinding head speed is 1100 rpm;

[0073] (4) The main drive speed is 1000 rpm;

[0074] (5) Grinding head current: 1#: 17.5A, 2#: 19.0A, 3#: 19.5A, 4#: 20A, 5#: 19A, 6#: 18.5A, 7#: 18.5A, 8#: 18A;

[0075] (6) Grinding head pressure: 1#: 0.15MPa, 2#: 0.18MPa, 3#: 0.22MPa, 4#: 0.25MPa, 5#: 0.2MPa, 6#: 0.15MPa, 7#: 0.15MPa, 8#: 0.10MPa;

[0076] Table 1 shows the amount of diameter reduction after peeling and the number of peeling cycles.

[0077] For the re-examination of the peeled and ground round steel, the magnetic flux leakage was controlled at 0.2mm, and the pass rate of comprehensive testing is shown in Table 1. Example 1

[0078] The second group of medium carbon non-cooled steel billets were slowly cooled. The billets were placed in the pit at a temperature of 640°C and cooled for 25 hours before being heated in a heating furnace at a temperature of 360°C.

[0079] The continuously cast billet enters a walking beam furnace for heating, with a secondary heating temperature of 1200℃ and a soaking temperature of 1170℃. The secondary heating temperature is 30℃ higher than the soaking temperature.

[0080] The heated continuous casting billet is descaled by high-pressure water at a pressure of 18 MPa.

[0081] After descaling, the continuously cast billet is rough rolled using a two-roll reversible rolling mill (φ1100×2500) with a large reduction rolling process. The rolling process is carried out in 11 passes, and the billet size is 205×205. The cooling water flow rate is controlled at 120m³ / h.

[0082] The rolled workpiece is cut off from the end defects of the rolled billet by a hydraulic shearing head with a cutting length of 100mm.

[0083] The rolled piece enters the intermediate rolling process. The six continuous rolling mills in the intermediate rolling mill are all arranged alternately in a horizontal and vertical configuration. The rolling mill consists of φ750×6 mills, all of which are fifth-generation short-stress rolling mills. The rolling temperature is 860℃, and the rolled piece size is Φ120mm.

[0084] The shearing section is Φ120mm, the shearing temperature is 860℃, the head length is 120mm, the tail length is 120mm, and the head and tail defects are removed.

[0085] The rolled piece enters the finishing rolling process. The finishing rolling mill consists of four continuous rolling mills arranged alternately in a horizontal and vertical configuration. The mills are composed of φ550×4, all of which are fifth-generation short-stress rolling mills. The rolling temperature is 850℃, the round steel specification is Φ100mm, and the finished product dimensional tolerance is controlled according to the upper limit positive tolerance of the second group of national standards.

[0086] The No. 2 flying shear has a cutting section of Φ100mm and a cutting temperature of 850℃. The No. 2 flying shear is divided into multiple length sections.

[0087] The flying shears are grouped together, and the round steel is cut into sections by three Φ1800mm metal saws (saw #1, moving saw, and saw #2). The sawing temperature is 700-850℃.

[0088] After being sawn, the round steel bars are placed on a cooling bed for air cooling and straightening; after beveling online, they are bundled, weighed, and put into storage.

[0089] The round steel bars were straightened and then subjected to flaw detection. The magnetic flux leakage was controlled within 0.2 mm. The initial pass rate of magnetic flux leakage detection is shown in Table 1.

[0090] Qualified round steel bars are bundled and stored; unqualified round steel bars are peeled using a φ180 twelve-head round steel peeling machine (grind wheel: φ500×100×203) and magnetic flux leakage flaw detection. The peeling process includes:

[0091] (1) The number of grinding heads used is 11;

[0092] (2) Grinding wheel usage: Grinding heads #1-4 use #16 grinding wheels, grinding heads #5-12 use #24 grinding wheels;

[0093] (3) The grinding head speed is 1450 rpm / min;

[0094] (4) The main drive speed is 750 rpm / min;

[0095] (5) Grinding head current: 1#: 18A, 2#: 23A, 3#: 23A, 4#: 23A, 5#: 22A, 6#: 22A, 7#: 22A, 8#: 22A, 9#: 20A, 10#: 20A, 11#: 18A;

[0096] (6) Grinding head pressure: The 12 grinding heads are divided into three groups. Grinding heads 1-4# are in one group with a pressure of 0.25MPa; grinding heads 5-8# are in the second group with a pressure of 0.2MPa; grinding heads 9-11# are in the third group with a pressure of 0.15MPa.

[0097] For the peeled and ground round steel, the magnetic flux leakage was 0.2 mm. The initial pass rate of magnetic flux leakage is shown in Table 1.

[0098] Table 1 shows the amount of diameter reduction after peeling and the number of peeling cycles.

[0099] For the peeled and ground round steel, the magnetic flux leakage was 0.2 mm. The pass rate of comprehensive testing is shown in Table 1. Example 2

[0100] The third group of medium carbon non-heated steel billets were slowly cooled. The billets were placed in the pit at a temperature of 640°C and cooled for 27 hours before being heated in a heating furnace at a temperature of 350°C.

[0101] The continuously cast billet enters a walking beam furnace for heating, with a secondary heating temperature of 1220℃ and a soaking temperature of 1160℃. The secondary heating temperature is 60℃ higher than the soaking temperature.

[0102] The heated continuous casting billet is descaled by high-pressure water at a pressure of 18 MPa.

[0103] After descaling, the continuously cast billet is rough rolled by a two-roll reversible rolling mill (φ1100×2500) using a high-reduction rolling process, with 11 rolling passes. The billet size is 205×205, and the cooling water flow rate is controlled at 110 m³ / h.

[0104] The rolled workpiece is cut off from the end defects of the rolled billet by a hydraulic shearing head with a cutting length of 100mm.

[0105] The rolled piece enters the intermediate rolling process. The six continuous rolling mills in the intermediate rolling mill are all arranged alternately in a horizontal and vertical configuration. The rolling mill consists of φ750×6 mills, all of which are fifth-generation short-stress rolling mills. The rolling temperature is 855℃, and the rolled piece size is Φ120mm.

[0106] The shearing section is Φ120mm, the shearing temperature is 855℃, the head length is 120mm, the tail length is 120mm, and the head and tail defects are removed.

[0107] The rolled piece enters the finishing rolling process. The finishing rolling mill consists of four continuous rolling mills arranged alternately in a horizontal and vertical configuration. The mills are composed of φ550×4, all of which are fifth-generation short-stress rolling mills. The rolling temperature is 850℃, the round steel specification is Φ100mm, and the finished product dimensional tolerance is controlled according to the upper limit positive tolerance of the second group of national standards.

[0108] The No. 2 flying shear has a cutting section of Φ100mm and a cutting temperature of 850℃. The No. 2 flying shear is divided into multiple length sections.

[0109] The flying shears are grouped together, and the round steel is cut into sections by three Φ1800mm metal saws (saw #1, moving saw, and saw #2). The sawing temperature is 700-850℃.

[0110] After being sawn, the round steel bars are placed on a cooling bed for air cooling and straightening; after beveling online, they are bundled, weighed, and put into storage.

[0111] The round steel bars were straightened and then subjected to flaw detection. The magnetic flux leakage was controlled within 0.2 mm. The initial pass rate of magnetic flux leakage detection is shown in Table 1.

[0112] Qualified round steel bars are bundled and stored; unqualified round steel bars are peeled using a φ180 twelve-head round steel peeling machine (grind wheel: φ500×100×203) and magnetic flux leakage flaw detection. The peeling process includes:

[0113] (1) The number of grinding heads used is 11;

[0114] (2) Grinding wheel usage: Grinding heads #1-4 use #16 grinding wheels, grinding heads #5-12 use #24 grinding wheels;

[0115] (3) The grinding head speed is 1450 rpm / min;

[0116] (4) The main drive speed is 750 rpm / min;

[0117] (5) Grinding head current: 1#: 18A, 2#: 22A, 3#: 22A, 4#: 22A, 5#: 23A, 6#: 23A, 7#: 23A, 8#: 23A, 9#: 20A, 10#: 20A, 11#: 18A;

[0118] (6) Grinding head pressure: The 12 grinding heads are divided into three groups. Grinding heads 1-4# are in one group with a pressure of 0.25MPa; grinding heads 5-8# are in the second group with a pressure of 0.2MPa; grinding heads 9-11# are in the third group with a pressure of 0.15MPa.

[0119] For the peeled and ground round steel, the magnetic flux leakage was 0.2 mm. The initial pass rate of magnetic flux leakage is shown in Table 1.

[0120] Table 1 shows the amount of diameter reduction after peeling and the number of peeling cycles.

[0121] For the peeled and ground round steel, the magnetic flux leakage was 0.2 mm. The pass rate of comprehensive testing is shown in Table 1. Example 3

[0122] The fourth group of medium carbon non-heated steel billets were slowly cooled. The billets were placed in the pit at a temperature of 640°C and cooled for 29 hours before being heated in a heating furnace at a temperature of 340°C.

[0123] The continuously cast billet enters a walking beam furnace for heating, with a secondary heating temperature of 1210℃ and a soaking temperature of 1170℃. The secondary heating temperature is 40℃ higher than the soaking temperature.

[0124] The heated continuous casting billet is descaled by high-pressure water at a pressure of 18 MPa.

[0125] After descaling, the continuously cast billet is rough rolled by a two-roll reversible rolling mill (φ1100×2500) using a high-reduction rolling process, with 11 rolling passes. The billet size is 205×205, and the cooling water flow rate is controlled at 130 m³ / h.

[0126] The rolled workpiece is cut off from the end defects of the rolled billet by a hydraulic shearing head with a cutting length of 100mm.

[0127] The rolled piece enters the intermediate rolling process. The six continuous rolling mills in the intermediate rolling mill are all arranged alternately in a horizontal and vertical configuration. The rolling mill consists of φ750×6 mills, all of which are fifth-generation short-stress rolling mills. The rolling temperature is 860℃, and the rolled piece size is Φ120mm.

[0128] The shearing section is Φ120mm, the shearing temperature is 860℃, the head length is 120mm, the tail length is 120mm, and the head and tail defects are removed.

[0129] The rolled piece enters the finishing rolling process. The finishing rolling mill consists of four continuous rolling mills arranged alternately in a horizontal and vertical configuration. The mills are composed of φ550×4, all of which are fifth-generation short-stress rolling mills. The rolling temperature is 850℃, the round steel specification is Φ100mm, and the finished product dimensional tolerance is controlled according to the upper limit positive tolerance of the second group of national standards.

[0130] The No. 2 flying shear has a cutting section of Φ100mm and a cutting temperature of 850℃. The No. 2 flying shear is divided into multiple length sections.

[0131] The flying shears are grouped together, and the round steel is cut into sections by three Φ1800mm metal saws (saw #1, moving saw, and saw #2). The sawing temperature is 700-850℃.

[0132] After being sawn, the round steel bars are placed on a cooling bed for air cooling and straightening; after beveling online, they are bundled, weighed, and put into storage.

[0133] The round steel bars were straightened and then subjected to flaw detection. The magnetic flux leakage was controlled within 0.2 mm. The initial pass rate of magnetic flux leakage detection is shown in Table 1.

[0134] Qualified round steel bars are bundled and stored; unqualified round steel bars are peeled using a φ180 twelve-head round steel peeling machine (grind wheel: φ500×100×203) and magnetic flux leakage flaw detection. The peeling process includes:

[0135] (1) The number of grinding heads used is 11;

[0136] (2) Grinding wheel usage: Grinding heads #1-4 use #16 grinding wheels, grinding heads #5-12 use #24 grinding wheels;

[0137] (3) The grinding head speed is 1450 rpm / min;

[0138] (4) The main drive speed is 750 rpm / min;

[0139] (5) Grinding head current: 1#: 18A, 2#: 24A, 3#: 24A, 4#: 24A, 5#: 21A, 6#: 21A, 7#: 21A, 8#: 21A, 9#: 20A, 10#: 20A, 11#: 18A;

[0140] (6) Grinding head pressure: The 12 grinding heads are divided into three groups. Grinding heads 1-4# are in one group with a pressure of 0.25MPa; grinding heads 5-8# are in the second group with a pressure of 0.2MPa; grinding heads 9-11# are in the third group with a pressure of 0.15MPa.

[0141] For the peeled and ground round steel, the magnetic flux leakage was 0.2 mm. The initial pass rate of magnetic flux leakage is shown in Table 1.

[0142] Table 1 shows the amount of diameter reduction after peeling and the number of peeling cycles.

[0143] For the peeled and ground round steel, the magnetic flux leakage was 0.2 mm. The pass rate of comprehensive testing is shown in Table 1. Example 4

[0144] The fifth group of medium carbon non-heated steel billets were slowly cooled. The billets were placed in the pit at a temperature of 650°C and cooled for 30 hours before being heated in a heating furnace at a temperature of 350°C.

[0145] The continuously cast billet enters a walking beam furnace for heating, with a secondary heating temperature of 1230℃ and a soaking temperature of 1160℃. The secondary heating temperature is 70℃ higher than the soaking temperature.

[0146] The heated continuous casting billet is descaled by high-pressure water at a pressure of 18 MPa.

[0147] After descaling, the continuously cast billet is rough rolled using a two-roll reversible rolling mill (φ1100×2500) with a large reduction rolling process. The rolling process is carried out in 11 passes, and the billet size is 205×205. The cooling water flow rate is controlled at 125 m³ / h.

[0148] The rolled workpiece is cut off from the end defects of the rolled billet by a hydraulic shearing head with a cutting length of 100mm.

[0149] The rolled piece enters the intermediate rolling process. The six continuous rolling mills in the intermediate rolling mill are all arranged alternately in a horizontal and vertical configuration. The rolling mill consists of φ750×6 mills, all of which are fifth-generation short-stress rolling mills. The rolling temperature is 860℃, and the rolled piece size is Φ120mm.

[0150] The shearing section is Φ120mm, the shearing temperature is 860℃, the head length is 120mm, the tail length is 120mm, and the head and tail defects are removed.

[0151] The rolled piece enters the finishing rolling process. The finishing rolling mill consists of four continuous rolling mills arranged alternately in a horizontal and vertical configuration. The mills are composed of φ550×4, all of which are fifth-generation short-stress rolling mills. The rolling temperature is 850℃, the round steel specification is Φ100mm, and the finished product dimensional tolerance is controlled according to the upper limit positive tolerance of the second group of national standards.

[0152] The No. 2 flying shear has a cutting section of Φ100mm and a cutting temperature of 850℃. The No. 2 flying shear is divided into multiple length sections.

[0153] The flying shears are grouped together, and the round steel is cut into sections by three Φ1800mm metal saws (saw #1, moving saw, and saw #2). The sawing temperature is 700-850℃.

[0154] After being sawn, the round steel bars are placed on a cooling bed for air cooling and straightening; after beveling online, they are bundled, weighed, and put into storage.

[0155] The round steel bars were straightened and then subjected to flaw detection. The magnetic flux leakage was controlled within 0.2 mm. The initial pass rate of magnetic flux leakage detection is shown in Table 1.

[0156] Qualified round steel bars are bundled and stored; unqualified round steel bars are peeled using a φ180 twelve-head round steel peeling machine (grind wheel: φ500×100×203) and magnetic flux leakage flaw detection. The peeling process includes:

[0157] (1) The number of grinding heads used is 11;

[0158] (2) Grinding wheel usage: Grinding heads #1-4 use #16 grinding wheels, grinding heads #5-12 use #24 grinding wheels;

[0159] (3) The grinding head speed is 1450 rpm / min;

[0160] (4) The main drive speed is 750 rpm / min;

[0161] (5) Grinding head current: 1#: 18A, 2#: 25A, 3#: 25A, 4#: 25A, 5#: 20A, 6#: 20A, 7#: 20A, 8#: 20A, 9#: 19A, 10#: 19A, 11#: 18A;

[0162] (6) Grinding head pressure: The 12 grinding heads are divided into three groups. Grinding heads 1-4# are in one group with a pressure of 0.25MPa; grinding heads 5-8# are in the second group with a pressure of 0.2MPa; grinding heads 9-11# are in the third group with a pressure of 0.15MPa.

[0163] For the peeled and ground round steel, the magnetic flux leakage was 0.2 mm. The initial pass rate of magnetic flux leakage is shown in Table 1.

[0164] Table 1 shows the amount of diameter reduction after peeling and the number of peeling cycles.

[0165] For the peeled and ground round steel, the magnetic flux leakage was 0.2 mm. The pass rate of comprehensive testing is shown in Table 1.

[0166] Table 1. Comparison of Process Test Parameters and Detection Results

[0167]

[0168] The initial magnetic flux leakage test pass rate for the first group of φ100 medium carbon non-rounded steel round bars was 59.6%, with a diameter reduction of 0.27-0.29 mm per peeling, requiring two peelings, resulting in a scrap rate of 12.4%. For groups 2-5, the initial magnetic flux leakage test pass rate for the second group of φ100 medium carbon non-rounded steel round bars was 77.2-79.2%, with a diameter reduction of 0.57-0.62 mm per peeling, requiring one peeling, resulting in a scrap rate of 0.7-1.5%. Compared with the original process, the magnetic flux leakage test pass rate for φ100 and V... The initial pass rate of magnetic flux leakage detection for 2908 medium carbon non-adjustable round steel was improved by more than 17.6%, the peeling and diameter reduction was increased by 0.3 mm, the number of peelings was reduced by 1, and the scrap rate was reduced by more than 10.9%. This invention can not only improve the initial pass rate of magnetic flux leakage detection and reduce the scrap rate of round steel, but also reduce the number of peelings, improve the peeling efficiency of grinding wheels, shorten the finishing cycle, and ensure the finishing delivery time of products. This invention can be promoted and applied in similar production lines of special steel.

[0169] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method of manufacturing a medium carbon non-rotated steel, characterized by, The steps are as follows: In the steel billet slow cooling process, the billet enters the slow cooling pit when the temperature is greater than or equal to 600℃, the slow cooling time is greater than or equal to 24 hours, and the billet temperature is greater than or equal to 300℃ before entering the heating furnace; In the steel billet heating process, the second heating temperature is 1200-1250℃, and the soaking temperature is 1150±20℃; In the high-pressure water descaling process, the descaling pressure is 18±1MPa; In the rough rolling process, the cooling water flow rate is controlled at 110-130 m 3 / h. In the process of grinding the unqualified round steel, the φ180 twelve-head round steel peeling machine is used, the grinding wheel specification is φ500x100x203, the magnetic flux leakage inspection defect material is peeled, the peeling diameter reduction is 0.6mm, and the peeling frequency is 1 time; In the process of grinding the unqualified round steel, the 1st-4th head uses 16# grinding wheel piece, and the 5th-12th head uses 24# grinding wheel piece; the 1st-4th head uses 16# grinding wheel piece, the 16# coarse grain grinding wheel increases the grinding amount, the 5th-12th head uses 24# grinding wheel piece, and the 24# fine grain grinding wheel ensures the surface quality; In the process of grinding the unqualified round steel, the 12 heads are divided into three groups, the 1st-4th head is a group, the pressure is 0.25MPa; the 5th-8th head is the second group, the pressure is 0.2MPa; and the 9th-12th head is the third group, the pressure is 0.15MPa.

2. The production method according to claim 1, wherein In the process of grinding the unqualified round steel, the number of grinding heads used is 10-12.

3. The production method according to claim 1, wherein In the process of grinding the unqualified round steel, the grinding head speed is 1450rpm.

4. The production method according to claim 1, wherein In the process of grinding the unqualified round steel, the main transmission speed is 750±50rpm.

5. The production method according to claim 1, wherein In the process of grinding the unqualified round steel, the grinding head current is 20-25A, wherein the 1st and 12th head current is controlled at 18A.

6. A medium carbon non-rotated steel, characterized by, Obtained by the manufacturing method according to any one of claims 1-5.

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