A method for controlling surface quality of 55SiCr spring steel wire

Abstract

The present invention relates to a method for controlling the surface quality of a 55SiCr spring steel wire rod. The method comprises the following steps: component control, billet grinding, heating, water descaling, rolling, controlled cooling, coiling, coil cooling and packaging. The billet grinding step adopts a 20-28 mesh grinding wheel and controls the feed amount to 12-15 mm to prevent the billet surface from overheating. The water descaling step controls the water descaling pressure to be ≥18 MPa. The rolling step adopts a laying head advance setting of 4-16%, sets the torque parameter of the pinch roller to 20-50%, and controls the overlap and non-overlap positions during coiling. The average temperature is ≤500℃, and the coil cooling process is cooled to below 150℃ at a rate of 0.1-0.5℃ / s before packaging. The 55SiCr spring steel with good coil shape is produced through quality control methods, avoiding scratches caused by local large circles and misaligned coils, and making the maximum depth of cracks, scars and scratches on the wire rod surface ≤40 microns; the average number of scratches per coil is reduced from 70-100 before improvement to ≤42, reducing the number and severity of scratches on the surface of 55SiCr spring steel wire products, and significantly improving the surface quality.

Description

Technical Field

[0001] The invention belongs to the technical field of spring steel production, and in particular relates to a method for controlling the surface quality of a 55SiCr spring steel wire. Background Art

[0002] 55SiCr spring steel is mostly used to manufacture automobile suspension springs, which is one of the key safety components of automobiles. Its surface defects are the main cause of early spring failure. Mid- and high-end spring steel wire factories have strict requirements on the number and depth of scratches on the surface of 55SiCr spring steel wires. If the number of scratches exceeds a certain number during factory flaw detection, the entire batch will be directly returned.

[0003] In the existing 55SiCr spring steel production method, due to the high alloy content of 55SiCr spring steel, it is easy to produce a 20-50μm martensite layer and cracks due to overheating during the billet grinding process. The overly thick and cracked martensite layer causes point-like peeling or scarring in the final wire product; the presence of decarburized structure on the surface of the spring steel will reduce the fatigue strength and service life of the spring steel; due to the presence of Si and Cr in the steel, an olivine oxide layer is easily formed, resulting in embedded iron sheet defects on the surface of the finished wire product; the ring shape is unstable after spinning, the surface state and coil shape are not good, and large and small circles and misaligned coils are prone to appear, resulting in scratches on the raised steel ring during lifting and transportation; improper phase transformation produces martensite and bainite structures, resulting in brittle fracture after packaging; improper coiling control causes the material to be too soft and scratched; the temperature of the spring steel after coiling is high, the internal stress is large, the surface hardness is low, and scratches are easily formed; the coil shape is poor after packaging, and the secondary reshipment of the wire packaging causes scratches.

[0004] Under the existing method, the average number of scratches per roll of 55SiCr spring steel is 70-100, and the surface cracks, scars, and scratches are deep. Therefore, it is necessary to consider using a production control method different from other types of wire in the production of 55SiCr spring steel wire to obtain a product with good surface condition. Summary of the invention

[0005] The present invention aims to solve at least one of the above technical problems to a certain extent. The present invention provides a method for controlling the surface quality of a 55SiCr spring steel wire, which reduces the number and severity of scratches on the surface of a finished 55SiCr spring steel wire and significantly improves the surface quality.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] A method for controlling the surface quality of a 55SiCr spring steel wire, the method comprising the following steps:

[0008] S1. Composition control: According to the weight percentage of the chemical composition of spring steel: C: 0.51-0.59%, Mn: 0.50-0.80%, Si: 1.20-1.60%, Cr: 0.50-0.80%, P≤0.020%, S≤0.015%, Ni≤0.25%, Cu≤0.25%, the balance is Fe and unavoidable impurities, and a steel billet is obtained;

[0009] S2. Billet grinding: The billet with controlled composition is ground with a 20-28 mesh grinding wheel to eliminate surface defects and decarburization of the billet. The feed amount is controlled at 12-15mm, the trolley running speed is 0.8-0.9m / s, and the total surface grinding amount is ≥1mm. The specific total grinding amount is adjusted according to the billet quality and decarburization requirements. The key to grinding control is to prevent the surface of the billet from overheating, forming a surface without a martensite layer or a closely bonded surface layer, and avoiding the formation of an overly thick and cracked martensite layer due to high alloy content of 55SiCr spring steel and overheating. After grinding, the billet is shot blasted and magnetic particle inspected. The defective position is repaired and shot blasted and inspected again to obtain a billet with good surface quality.

[0010] S3. Heating: The steel billet after grinding is heated at a low temperature to prevent decarburization. The high temperature section temperature is controlled at 1000-1100℃ during heating, and the furnace time is ≤120min to avoid the presence of decarburization on the surface and reduce the fatigue strength and service life of the spring steel.

[0011] S4. Water descaling: The heated billet is descaled with high-pressure water to remove the primary iron oxide scale. The water descaling pressure is controlled to be ≥18MPa, the descaling roller speed is ≤1m / s, and the nozzle impact force is ≥0.8N / mm 2 The billet is accurately aligned when entering the descaling ring to avoid the formation of olivine oxide layer in the steel by Si and Cr, which may lead to embedded iron scale defects on the surface of the finished wire;

[0012] S5. Rolling: The steel billet after water descaling is rolled into a rolling line including a finishing mill, a sizing mill, a laying head and a cooling line to be rolled into wire rods. The temperature of the steel billet entering the finishing mill is controlled to be 850-950°C, the temperature entering the sizing mill is 860-950°C, the laying temperature is 820-860°C, the advance amount of the laying head of 5.5-10mm specification is set to 8-16%, and the advance amount of the laying head of 11-16mm specification is set to 4-10%. The temperature and advance amount are set to ensure the stability of the coil shape after laying, avoid the occurrence of large and small coils and misaligned coils, and thus avoid the raised coil from being scratched during lifting and transportation; in order to ensure the stability of the coil shape, especially the stability of the tail coil shape, it is required that the tension between the front pinch roller and the sizing mill of the laying head is appropriate, and the torque parameter of the pinch roller, that is, the percentage of the actual torque to the rated torque, is set to 20-50%;

[0013] S6. Controlled cooling: When the wire rod after spinning is controlled to cool on the cooling line, the fan opening, the insulation cover opening and the roller speed are controlled according to the specifications of the 55SiCr spring steel produced. The wire rod is controlled to enter the insulation cover at a cooling rate of 0.5-2℃ / s before entering the insulation cover. The temperature entering the cover is 680-720℃, and the phase transformation is completed in the cover at a cooling rate of ≤1℃ / s. Through the controlled cooling process, the 55SiCr spring steel obtains fine pearlite structure to avoid the occurrence of martensite and bainite structures that lead to brittle fracture after packaging;

[0014] S7, coiling: After rolling and controlled cooling, the wire enters the coiling device for coiling. The overlapping and non-overlapping positions are controlled to be ≤500℃ during coiling to prevent the material from being too soft and causing scratches. A distributor is installed on the upper part of the coiling drum of the coiling device. The distributor speed is controlled to match the speed of the last roller to make the coils evenly arranged. According to the different specifications of 55SiCr spring steel, the speed of the last roller is set to 0.30-0.50m / s, and the corresponding distributor speed is 20-30rpm to obtain a coil with good surface condition and coil shape;

[0015] S8, coil cooling: a bifurcated extension section is set on the PF line, and the PF line speed is 0.2-0.3m / s. The coils after winding enter the bifurcated extension section through the PF line, and insulation measures are added to cool the coils to below 150℃ at a speed of 0.1-0.5℃ / s. By cooling naturally to a suitable temperature, the internal stress is reduced and the surface hardness is increased, so as to avoid the high temperature of the coils after winding, which leads to the high temperature of the baler and easy scratches;

[0016] S9. Packaging: The cooled coils are packed with packing wire by a packing machine, and the packing pressure is set to 15-30t. During packing, a flexible wear-resistant pad is used between the packing wire and the coil to prevent scratches between the packing wire and the coil. At the same time, due to the low temperature, the coils with good coil shape after packaging can avoid scratches caused by local large circles and misaligned coils during transportation, meet the conditions for re-packaging, and avoid scratches caused by secondary transportation, so as to obtain 55SiCr spring steel wire rods. The maximum depth of surface cracks, scars, and scratches of 55SiCr spring steel wire rods is ≤40 microns, and the average number of scratches per coil is ≤42.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) Through appropriate grinding process, using 20-28 mesh grinding wheel, controlling the feed amount to 12-15mm, shot blasting and flaw detection, the surface of the steel billet is prevented from overheating, and the martensite layer is too thick and cracked to obtain a steel billet with good surface quality.

[0019] (2) Use low-temperature heating technology to prevent decarburization, and use high-pressure water descaling of ≥18MPa to remove primary iron oxide and avoid embedded iron defects.

[0020] (3) Appropriate rolling and controlled cooling system, with temperature, 4-16% lead and 20-50% of the pinch roll torque parameters to ensure the stability of the ring shape, especially the stability of the tail ring shape, to avoid scratches, and controlled cooling to obtain fine pearlite structure to avoid brittle fracture after packaging.

[0021] (4) The speed of the distributor is controlled by winding to match the speed of the last roller. The winding temperature is ≤500℃ to prevent the material from being too soft and causing scratches.

[0022] (5) On the PF line, the steel is naturally cooled to a suitable temperature, cooled to below 150°C at a rate of 0.1-0.5°C / s before packaging to reduce internal stress and increase surface hardness to prevent scratches during packaging.

[0023] (6) Control the packing pressure to 15-30t and use flexible wear-resistant pads for protection, so that the coils with good coil shape after packing can be prevented from being scratched due to local large circles and misaligned coils during transportation.

[0024] In summary, the quality control method is used to produce 55SiCr spring steel with good coil shape, so that the maximum depth of cracks, scars and scratches on the wire rod surface is ≤40 microns; the average number of scratches per coil is reduced from 70-100 before improvement to ≤42, reducing the number and severity of scratches on the surface of the finished 55SiCr spring steel wire, and significantly improving the surface quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0026] Figure 1 This is a low-magnification comparison diagram of the steel billet surface layer of Example 1 of the present invention and Comparative Example 1;

[0027] Figure 1 middle: Figure 1 (a) shows a low-magnification image of the steel billet surface of Example 1; Figure 1 (b) shows a low-magnification image of the steel billet surface of Comparative Example 1.

[0028] Figure 2 1 is a comparison diagram of the wire rods of Example 1 of the present invention and Comparative Examples 1 and 2;

[0029] Figure 2 middle: Figure 2 (c) represents the wire rod diagram of Example 1; Figure 2 (d) represents the wire rod diagram of Comparative Example 1; Figure 2 (e) shows the wire rod diagram of Comparative Example 2. DETAILED DESCRIPTION

[0030] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0031] Example 1

[0032] The present invention describes a A preferred embodiment of the surface quality control method of specification 55SiCr spring steel wire comprises the following steps:

[0033] S1. Composition control: According to the weight percentage of the chemical composition of spring steel: C: 0.56%, Si: 1.47%, Mn: 0.68%, Cr: 0.71%, P: 0.010%, S: 0.003%, Ni: 0.018%, Cu: 0.012%, the balance is Fe and unavoidable impurities, and a steel billet is obtained;

[0034] S2. Billet grinding: The billet with controlled composition is ground with a 24-mesh grinding wheel, the feed amount is controlled to be 12mm, the trolley running speed is 0.8m / s, and the total surface grinding amount is 2mm. After the grinding, the billet is shot blasted and magnetic particle inspected. The defective position is spot repaired and shot blasted and inspected again to obtain a billet with good surface quality;

[0035] S3, Heating: The steel billet after grinding is heated at a low temperature to prevent decarburization. The temperature of the high temperature section is controlled at 1050℃ during heating, and the furnace time is 100min.

[0036] S4. Water descaling: The heated billet is descaled with high-pressure water to remove the primary iron oxide scale. The water descaling pressure is controlled at 20MPa, the descaling roller speed is 0.8m / s, and the nozzle impact force is 1.0N / mm 2 , the billet is accurately centered when entering the descaling ring;

[0037] S5. Rolling: The steel billet after water descaling is rolled into a rolling line including a finishing mill, a sizing mill, a laying head and a cooling line to be rolled into wire rods. The temperature of the steel billet entering the finishing mill is controlled to be 900°C, the temperature entering the sizing mill is controlled to be 880°C, the laying head temperature is controlled to be 840°C, the leading amount of the laying head is set to 4%, and the torque parameter of the pinch roll, i.e., the percentage of the actual torque to the rated torque, is set to 30%;

[0038] S6, controlled cooling: When the wire rod after spinning is controlled cooling on the cooling line, the wire rod is controlled to enter the insulation cover at a cooling rate of 0.5-2℃ / s before entering the insulation cover, 3 insulation covers are turned on, 1 fan is turned on 70%, the temperature of the cover is 710℃ at the overlap point and 690℃ at the non-overlap point, and the phase change is completed in the cover at a cooling rate of ≤1℃ / s, and the speed of the first roller is set to 0.34m / s;

[0039] S7, coiling: the wire rod after rolling and controlled cooling enters the coiling device for coiling. The overlapping and non-overlapping positions are controlled to be 480°C during coiling. A distributor is installed on the upper part of the coiling drum of the coiling device. The speed of the distributor is controlled to match the speed of the last roller. The speed of the last roller is set to 0.4m / s, and the corresponding distributor speed is 20rpm, so as to obtain a coil with good surface condition and coil shape.

[0040] S8, coil cooling: a forked extension section is set on the PF line, the PF line speed is 0.2-0.3m / s, the coil after collection is transported to the forked extension section of the PF line by the C-type hook, and insulation measures are added to make the maximum temperature of the coil reach 80℃ after 120 minutes;

[0041] S9. Packing: The cooled coil is packed with packing wire by a packing machine. The packing pressure is set to 15t. During packing, a flexible wear-resistant pad is used between the packing wire and the coil to obtain 55SiCr spring steel wire rod.

[0042] Example 2

[0043] The present invention describes a A preferred embodiment of the surface quality control method of specification 55SiCr spring steel wire comprises the following steps:

[0044] S1. Composition control: According to the weight percentage of the chemical composition of spring steel: C: 0.55%, Si: 1.47%, Mn: 0.68%, Cr: 0.70%, P: 0.010%, S: 0.003%, Ni: 0.018%, Cu: 0.012%, the balance is Fe and unavoidable impurities, and a steel billet is obtained;

[0045] S2. Billet grinding: The billet with controlled composition is ground with a 24-mesh grinding wheel, the feed amount is controlled to be 14mm, the trolley running speed is 0.8m / s, and the total surface grinding amount is 2mm. After grinding, the billet is shot blasted and magnetic particle inspected. The defective position is spot repaired and shot blasted and inspected again to obtain a billet with good surface quality;

[0046] S3, Heating: The steel billet after grinding is heated at a low temperature to prevent decarburization. The temperature of the high temperature section is controlled at 1030℃ during heating, and the furnace time is 90min.

[0047] S4. Water descaling: The heated billet is descaled with high-pressure water to remove the primary iron oxide scale. The water descaling pressure is controlled at 20MPa, the descaling roller speed is 0.8m / s, and the nozzle impact force is 1.0N / mm 2 , the billet is accurately centered when entering the descaling ring;

[0048] S5. Rolling: The steel billet after water descaling is rolled into a rolling line including a finishing mill, a sizing mill, a laying head and a cooling line to be rolled into wire rods. The temperature of the steel billet entering the finishing mill is controlled to be 900°C, the temperature entering the sizing mill is controlled to be 880°C, the laying head temperature is controlled to be 840°C, the leading amount of the laying head is set to 4%, and the torque parameter of the pinch roll, i.e., the percentage of the actual torque to the rated torque, is set to 30%;

[0049] S6, controlled cooling: When the wire rod after spinning is controlled cooling on the cooling line, the wire rod is controlled to enter the insulation cover at a cooling rate of 0.5-2℃ / s before entering the insulation cover, and 3 insulation covers are turned on, and 2 fans are turned on 70% and 30% respectively. The temperature of the cover is 710℃ at the overlap point and 690℃ at the non-overlap point. The phase change is completed in the cover at a cooling rate of ≤1℃ / s, and the speed of the first roller is set to 0.34m / s;

[0050] S7, coiling: the wire rod after rolling and controlled cooling enters the coiling device for coiling. The overlapping and non-overlapping positions are controlled to be 480°C during coiling. A distributor is installed on the upper part of the coiling drum of the coiling device. The speed of the distributor is controlled to match the speed of the last roller. The speed of the last roller is set to 0.4m / s, and the corresponding distributor speed is 20rpm, so as to obtain a coil with good surface condition and coil shape.

[0051] S8, coil cooling: a forked extension section is set on the PF line, the PF line speed is 0.2-0.3m / s, the coil after collection is transported to the forked extension section of the PF line by the C-type hook, and insulation measures are added to make the maximum temperature of the coil reach 80℃ after 120 minutes;

[0052] S9. Packing: The cooled coil is packed with packing wire by a packing machine. The packing pressure is set to 15t. During packing, a flexible wear-resistant pad is used between the packing wire and the coil to obtain 55SiCr spring steel wire rod.

[0053] Example 3

[0054] The present invention describes a A preferred embodiment of the surface quality control method of specification 55SiCr spring steel wire comprises the following steps:

[0055] S1. Composition control: According to the weight percentage of the chemical composition of spring steel: C: 0.56%, Si: 1.47%, Mn: 0.68%, Cr: 0.71%, P: 0.010%, S: 0.003%, Ni: 0.018%, Cu: 0.012%, the balance is Fe and unavoidable impurities, and a steel billet is obtained;

[0056] S2. Billet grinding: The billet with controlled composition is ground with a 24-mesh grinding wheel, the feed amount is controlled to be 12mm, the trolley running speed is 0.8m / s, and the total surface grinding amount is 2mm. After the grinding, the billet is shot blasted and magnetic particle inspected. The defective position is spot repaired and shot blasted and inspected again to obtain a billet with good surface quality;

[0057] S3, Heating: The steel billet after grinding is heated at a low temperature to prevent decarburization. The temperature of the high temperature section is controlled at 1050℃ during heating, and the furnace time is 100min.

[0058] S4. Water descaling: The heated billet is descaled with high-pressure water to remove the primary iron oxide scale. The water descaling pressure is controlled at 20MPa, the descaling roller speed is 0.8m / s, and the nozzle impact force is 1.0N / mm 2 , the billet is accurately centered when entering the descaling ring;

[0059] S5, rolling: the steel billet after water descaling enters the rolling line including the finishing mill, the reducing and sizing mill, the laying head and the cooling line to be rolled into wire rod, the temperature of the steel billet entering the finishing mill is controlled to be 880°C, the temperature entering the reducing and sizing mill is 860°C, the laying head temperature is 830°C, the leading amount of the laying head is set to 6%, and the torque parameter of the pinch roll, i.e., the percentage of the actual torque to the rated torque, is set to 20%;

[0060] S6, controlled cooling: When the wire rod after spinning is controlled cooling on the cooling line, the wire rod is controlled to enter the insulation cover at a cooling rate of 0.5-2℃ / s before entering the insulation cover, 3 insulation covers are turned on, 1 fan is turned on 70%, the temperature of the cover is 710℃ at the overlap point and 690℃ at the non-overlap point, and the phase change is completed in the cover at a cooling rate of ≤1℃ / s, and the speed of the first roller is set to 0.34m / s;

[0061] S7, coiling: the wire rod after rolling and controlled cooling enters the coiling device for coiling. The overlapping and non-overlapping positions are controlled to be 480°C during coiling. A distributor is installed on the upper part of the coiling drum of the coiling device. The speed of the distributor is controlled to match the speed of the last roller. The speed of the last roller is set to 0.4m / s, and the corresponding distributor speed is 20rpm, so as to obtain a coil with good surface condition and coil shape.

[0062] S8, coil cooling: a forked extension section is set on the PF line, the PF line speed is 0.2-0.3m / s, the coil after collection is transported to the forked extension section of the PF line by the C-type hook, and insulation measures are added to make the maximum temperature of the coil reach 80℃ after 120 minutes;

[0063] S9. Packing: The cooled coil is packed with packing wire by a packing machine. The packing pressure is set to 15t. During packing, a flexible wear-resistant pad is used between the packing wire and the coil to obtain 55SiCr spring steel wire rod.

[0064] Example 4

[0065] The present invention describes a A preferred embodiment of the surface quality control method of specification 55SiCr spring steel wire comprises the following steps:

[0066] S1. Composition control: According to the weight percentage of the chemical composition of spring steel: C: 0.56%, Si: 1.47%, Mn: 0.68%, Cr: 0.71%, P: 0.010%, S: 0.003%, Ni: 0.018%, Cu: 0.012%, the balance is Fe and unavoidable impurities, and a steel billet is obtained;

[0067] S2. Billet grinding: The billet with controlled composition is ground with a 24-mesh grinding wheel, the feed amount is controlled to be 12mm, the trolley running speed is 0.8m / s, and the total surface grinding amount is 2mm. After the grinding, the billet is shot blasted and magnetic particle inspected. The defective position is spot repaired and shot blasted and inspected again to obtain a billet with good surface quality;

[0068] S3, Heating: The steel billet after grinding is heated at a low temperature to prevent decarburization. The temperature of the high temperature section is controlled at 1050℃ during heating, and the furnace time is 100min.

[0069] S4. Water descaling: The heated billet is descaled with high-pressure water to remove the primary iron oxide scale. The water descaling pressure is controlled at 20MPa, the descaling roller speed is 0.8m / s, and the nozzle impact force is 1.0N / mm 2 , the billet is accurately centered when entering the descaling ring;

[0070] S5, rolling: the steel billet after water descaling enters the rolling line including the finishing mill, the reducing and sizing mill, the laying head and the cooling line to be rolled into wire rod, the temperature of the steel billet entering the finishing mill is controlled to be 880°C, the temperature entering the reducing and sizing mill is 860°C, the laying head temperature is 830°C, the leading amount of the laying head is set to 10%, and the torque parameter of the pinch roller, i.e., the percentage of the actual torque to the rated torque, is set to 20%;

[0071] S6, cooling control: When the wire rod after spinning is cooled in the cooling line, the wire rod is controlled to enter the insulation cover at a cooling rate of 0.5-2℃ / s before entering the insulation cover, 3 insulation covers are turned on, 1 fan is turned on by 60%, the temperature of the cover is 710℃ at the overlap point and 680℃ at the non-overlap point, and the phase change is completed in the cover at a cooling rate of ≤1℃ / s, and the speed of the first roller is set to 0.34m / s;

[0072] S7, coiling: the wire rod after rolling and controlled cooling enters the coiling device for coiling. The overlapping and non-overlapping positions are controlled to be 480°C during coiling. A distributor is installed on the upper part of the coiling drum of the coiling device. The speed of the distributor is controlled to match the speed of the last roller. The speed of the last roller is set to 0.4m / s, and the corresponding distributor speed is 20rpm, so as to obtain a coil with good surface condition and coil shape.

[0073] S8, coil cooling: a forked extension section is set on the PF line, the PF line speed is 0.2-0.3m / s, the coil after collection is transported to the forked extension section of the PF line by the C-type hook, and insulation measures are added to make the maximum temperature of the coil reach 80℃ after 120 minutes;

[0074] S9. Packing: The cooled coil is packed with packing wire by a packing machine. The packing pressure is set to 15t. During packing, a flexible wear-resistant pad is used between the packing wire and the coil to obtain 55SiCr spring steel wire rod.

[0075] Comparative Example 1:

[0076] A sort of The production method of 55SiCr spring steel wire rod includes composition control, billet grinding, heating, water descaling, rolling, cooling, coiling, coil cooling and packaging. The method is different from that of Example 1 in that: (1) Billet grinding: The billet with controlled composition is ground with a 16-mesh grinding wheel, and the feed amount is controlled to be 18 mm. After the grinding, the billet is not subjected to shot blasting or flaw detection; (2) Water descaling: The heated billet is descaled with high-pressure water to remove primary iron oxide scale, and the water descaling pressure is controlled to be 10 MPa; and a 55SiCr spring steel wire rod is obtained.

[0077] Comparative Example 2:

[0078] A sort of A method for producing a 55SiCr spring steel wire rod includes the steps of component control, steel billet grinding, heating, water descaling, rolling, cooling, coiling, coil cooling and packaging. The method is different from that of Example 1 in that: (1) steel rolling: the advance amount of the laying head is set to 2%, and the torque parameter of the pinch roller, i.e., the percentage of the actual torque to the rated torque, is set to 10%; (2) packaging: the cooled coil is packaged by a packaging machine with a packaging wire, the packaging pressure is set to 35 tons, and no protective measures are used between the packaging wire and the coil during packaging, thereby obtaining a 55SiCr spring steel wire rod.

[0079] The crack depth and scar depth of the 55SiCr spring steel wire rod were measured by metallographic method after pickling the wire rod in Examples 1-4 and Comparative Examples 1-2, and the number of scratches was measured by eddy current flaw detection method. The results are shown in Table 1 below:

[0080]

[0081]

[0082] The results are shown in the attached figure. Figure 1 (a) The surface quality of the steel billet is good, indicating that the grinding is appropriate; Figure 1 (b) Surface defects on the billet surface indicate improper grinding; Figure 2 (c) The surface quality of the wire rod is good, indicating that the quality control is appropriate; Figure 2 (d) The presence of scars on the wire rod surface indicates poor quality control; Figure 2 (e) Scratches on the wire rod surface indicate poor quality control.

[0083] From the comparison results of the above table and the attached drawings, it can be seen that the present invention adopts a suitable grinding process, adopts a 20-28 mesh grinding wheel, controls the feed amount to 12-15mm, shot blasting, and flaw detection to prevent the surface of the steel billet from overheating, avoids an overly thick and cracked martensite layer, and obtains a steel billet with good surface quality; adopts a low-temperature heating process to prevent decarburization; removes primary iron oxide scale by high-pressure water descaling of ≥18MPa to avoid embedded iron scale defects; a suitable rolling and controlled cooling system is used to ensure the stability of the ring shape and avoid scratches with temperature, 4-16% advance amount and 20-50% torque parameters of the pinch roller torque, and controls cooling to obtain fine pearlite structure to avoid brittle fracture after packaging; through the protection of the roller and coiling equipment, the distributor speed is controlled to match the speed of the last roller, and the coiling temperature is controlled to be ≤500℃ Prevent scratches caused by excessive softening of the material, and obtain coils with good surface condition and coil shape; on the PF line, naturally cool to the appropriate temperature, cool to below 150℃ at a rate of 0.1-0.5℃ / s before packaging, reduce internal stress and increase surface hardness, and prevent scratches during packaging; control the packaging pressure to 15-30t, use flexible wear-resistant pads for protection, so that the coils with good coil shape after packaging can avoid scratches caused by local large circles and misaligned coils during transportation, and produce 55SiCr spring steel with good coil shape through a new quality control method, so that the maximum depth of cracks, scars and scratches on the surface of the wire rod is ≤40 microns; the average number of scratches per coil is reduced from 70-100 before improvement to ≤42, and the surface quality is significantly improved.

[0084] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. All equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for controlling the surface quality of a 55SiCr spring steel wire, characterized in that: The method includes composition control, billet grinding, heating, water descaling, rolling, controlled cooling, coiling, coil cooling and packaging processes; The steel billet grinding process uses a 20-28 mesh grinding wheel, controls the feed amount to 12-15mm, and the total surface grinding amount is ≥1mm; The water descaling is controlled by the water descaling pressure ≥ 18MPa, the descaling roller speed ≤ 1m / s, and the nozzle impact force ≥ 0.8N / mm 2 , the billet is accurately centered when entering the descaling ring; The rolling process controls the spinning temperature to 820-860°C, sets the advance amount of the spinning machine with a specification of 5.5-10 mm to 8-16% and the advance amount of the spinning machine with a specification of 11-16 mm to 4-10%, and sets the torque parameter of the pinch roller, that is, the percentage of the actual torque to the rated torque to 20-50%; The controlled cooling process controls the wire to enter the heat preservation cover at a cooling rate of 0.5-2°C / s before entering the heat preservation cover, the temperature entering the cover is 680-720°C, and the phase change is completed in the cover at a cooling rate of ≤1°C / s; The coiling process controls the overlapping and non-overlapping positions during coiling to be ≤500°C; The coil cooling process is performed at a speed of 0.1-0.5°C / s to cool the coil to below 150°C before packaging, and the packaging pressure is set to 15-30t.

2. The method for controlling the surface quality of a 55SiCr spring steel wire according to claim 1, characterized in that: The trolley running speed of the steel billet grinding process is 0.8-0.9m / s. After the grinding is completed, shot blasting and magnetic particle inspection are carried out. The defective positions are repaired and shot blasted and inspected again.

3. The method for controlling the surface quality of a 55SiCr spring steel wire according to claim 1, characterized in that: During the heating process, the temperature of the high temperature section is controlled at 1000-1100° C., and the time in the furnace is ≤120 min.

4. The method for controlling the surface quality of a 55SiCr spring steel wire according to claim 1, characterized in that: The rolling process controls the temperature of the steel billet entering the finishing mill to be 850-950°C, and the temperature entering the sizing mill to be 860-950°C.

5. The method for controlling the surface quality of a 55SiCr spring steel wire according to claim 1, characterized in that: In the roll collection process, a distributor is installed on the upper part of the roll collection drum, and the rotation speed of the distributor is controlled to match the speed of the last roller. The speed of the last roller is set to 0.30-0.50m / s, and the corresponding distributor rotation speed is 20-30rpm.

6. The method for controlling the surface quality of a 55SiCr spring steel wire according to claim 1, characterized in that: In the coil cooling process, a bifurcated extension section is arranged on the PF line, the PF line speed is 0.2-0.3 m / s, and the coil after being rolled enters the bifurcated extension section through the PF line.

7. The method for controlling the surface quality of a 55SiCr spring steel wire according to claim 1, characterized in that: In the packaging process, a flexible wear-resistant protective pad is used between the packaging wire and the coil.

8. A method for controlling the surface quality of a 55SiCr spring steel wire according to any one of claims 1 to 7, characterized in that: The maximum depth of surface cracks, scars and scratches of the 55SiCr spring steel wire rod is ≤40 microns, and the average number of scratches per roll is ≤42.

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