A method for manufacturing steel for cold-dip galvanized automotive brake mufflers

Abstract

This invention discloses a cold-based galvanized steel for automotive brake mufflers and its production method. The chemical composition of the steel plate includes: C: 0.05-0.15%, Si: 0.01-0.05%, Mn: 0.3-0.8%, P: 0.01-0.03%, S: 0.005-0.012%, Al: 0.02-0.2%, Ti: 0.015-0.035%. The production method includes: (1) refining and continuously casting molten iron to obtain a slab; (2) heating the slab, hot rolling, coiling, pickling, and cold rolling to obtain a cold-based galvanized base material; (3) annealing the cold-based galvanized base material, galvanizing it in a zinc pot, and then cooling it in sections, finishing, straightening, and cleaning to obtain the final product. The automotive brake muffler steel provided by this invention has excellent corrosion resistance and good wear resistance, solving the problems of poor corrosion resistance and easy wear of existing automotive brake muffler steel.

Description

Technical Field

[0001] This invention belongs to the field of automotive steel technology, specifically relating to a method for manufacturing cold-dip galvanized steel for automotive brake mufflers. Background Technology

[0002] With the continuous development of automotive lightweighting and the need for cost reduction and efficiency improvement, automotive brake pads are also constantly evolving towards lower costs. Automotive brake dampers are generally composed of thin steel sheets, an adhesive heat insulation layer, and friction blocks. Nowadays, the steel sheets used for brake dampers are gradually shifting from stainless steel sheets to ordinary cold-rolled sheets. The working environment of brake damper steel sheets often involves high temperatures, vibration, and friction, requiring materials with certain corrosion resistance and wear resistance. However, the poor corrosion resistance and easy wear of cold-rolled sheets have consistently limited their widespread application in dampers.

[0003] Chinese patent CN106148823A discloses a 550MPa high-strength structural grade galvanized steel strip with the following chemical composition by mass percentage: C: 0.04-0.06%, Mn: 0.15-0.30%, Si≤0.03%, S≤0.015%, P≤0.022%, Als: 0.025-0.06%, N≤0.0050%, with the remainder being iron and unavoidable impurities. It utilizes a composition design that strengthens through Si and Mn solid solution, employing hot-rolled controlled rolling and cooling, cold-rolled hardening, and low-temperature annealing galvanizing processes to achieve the development of high-strength galvanized steel strip. However, it is limited to a pure zinc coating, and its corrosion resistance and wear resistance are not mentioned.

[0004] Chinese patent CN103882202A discloses a method for manufacturing continuously annealed high-strength hot-dip galvanized steel. The specific chemical composition (mass percentage) of the substrate of this invention is as follows: C: 0.02-0.04%, Si: 0.001-0.03%, Mn: 0.10-0.40%, P: 0.001-0.015%, S: 0.001-0.010%, B: 0.0010-0.0020%, with the balance being Fe and unavoidable inclusions. The material's mechanical properties range from a yield strength of 550-650 MPa to a tensile strength of 570-670 MPa. The microstructure is a ferritic fibrous structure. The final product specifications are 0.2-1.2 mm. It is suitable for roll forming in construction and for processing pull rings for food cans requiring high hardness, exhibiting good bending performance. However, the corrosion resistance and wear resistance of the coating are not mentioned, therefore, it cannot be concluded that it is suitable for use as steel for brake pads and mufflers.

[0005] ZAM (zinc-aluminum-magnesium) coating is a coating material with excellent corrosion resistance, reasonable cost, and long service life, reaching up to 30 years under natural conditions, making it an effective replacement for stainless steel products. ZAM coating also exhibits excellent resistance to red rust and self-healing corrosion protection at shear fracture surfaces. The Chinese literature "Development and Application Progress of Hot-Dip Zinc-Aluminum-Magnesium Coatings" points out that ZAM coatings have a lower coefficient of friction than pure zinc (GI) and electroplated zinc (EG) coatings. While the coefficients of friction for GI and EG increase with the number of measurements, the coefficient of friction for ZAM coatings remains low and stable, not increasing with the number of measurements. The low coefficient of friction and stable friction characteristics of ZAM coatings reduce coating wear and, while ensuring corrosion resistance, also improve wear resistance. Therefore, it is necessary to develop a ZAM-coated steel for automotive brake dampers. Summary of the Invention

[0006] The purpose of this invention is to provide a cold-rolled galvanized steel for automotive brake mufflers and its production method, so as to solve the problems of poor corrosion resistance and easy wear of existing cold-rolled automotive brake muffler steel.

[0007] The chemical composition of the cold-plated galvanized steel for automotive brake mufflers described in this invention includes (wt%): C: 0.05–0.15%, Si: 0.01–0.05%, Mn: 0.3–0.80%, P: 0.01–0.03%, S: 0.005–0.012%, Al: 0.02–0.2%, Ti: 0.015–0.035%, with the remainder being Fe and other impurity elements. Its yield strength is ≥660 MPa, tensile strength is ≥700 MPa, and elongation (A... 50 ≥5%, flatness ≤2mm / 5m, coating hardness 100HV~200HV, coating thickness 5~30μm.

[0008] The production method of cold-based galvanized automotive brake muffler steel according to the present invention includes the following steps: (1) after smelting molten iron, it is refined and continuously cast to obtain a slab; (2) the slab is heated and then hot-rolled, coiled, straightened, pickled and cold-rolled to obtain a cold-based galvanized base material; (3) the cold-based galvanized base material is annealed, galvanized in a zinc pot, and then cooled in sections, finished, straightened and cleaned to obtain the final product.

[0009] Further, in step (2) of the present invention, the heating temperature is 1200-1280℃ and the holding time is 180-240min; the final rolling temperature of the hot rolling is 870-940℃ and the coiling temperature is 450-540℃, resulting in a hot coil with a strip thickness of 1.8-4.0mm.

[0010] Furthermore, in step (2) of the present invention, the pickling process involves a stretching elongation of 0.8 to 2.0%, a bending roller insertion of 10 to 20 mm, and a straightening roller insertion of 6 to 12 mm.

[0011] Furthermore, in step (2) of the present invention, the cold rolling has a cold rolling reduction rate of 50-90%, an IU value of ≤3, an F5 cold rolling mill roughness of 4.0-5.0μm, a base material thickness of 0.3-1.8mm, a reflectivity of ≥70%, and a roughness of 0.7-1.0μm.

[0012] Further, the specific operation of the cold-based galvanized base material annealing in step (3) of the present invention is as follows: the galvanized base material is heated to 500℃~600℃ at a rate of 0.5℃ / s~5℃ / s, the heat soaking time is 100s~180s, and then cooled to 430℃~460℃ at a rate of 10℃ / s~20℃ / s.

[0013] Furthermore, in step (4) of the present invention, the zinc plating in the zinc pot has a dew point temperature of -20 to -10°C and a zinc liquid temperature of 430 to 450°C.

[0014] Furthermore, the zinc bath used for zinc plating in step (4) of this invention contains 1-5% Al, 0.8-3% Mg, 0.08-0.12% Si, 0.01-0.05% Fe, and 0.01-0.03% Ce by mass, and the coating composition is the same as that of the zinc bath. The presence of Fe reduces the loss caused by the dissolution of the substrate in the zinc bath, and at the same time, FeAl and Fe-Al-Zn compounds are formed on the substrate surface during the coating process, which improves the bonding force and adhesion between the coating and the steel plate. Ce has the effect of reducing the corrosion potential of the coating, thereby further improving the corrosion resistance of the coating. The addition of Si helps to improve the wettability of the strip steel and the zinc bath and reduce the coefficient of friction of the coating.

[0015] Furthermore, the segmented cooling in step (4) of the present invention includes a first cooling and a second cooling.

[0016] The first cooling method of this invention is gas cooling, with a cooling rate of 10-25℃ / s and a final temperature of 290-320℃. The cooling rate is precisely controlled so that the molten solidification line of the coating is 3-9m away from the zinc liquid surface.

[0017] The second cooling method of this invention is water mist cooling, with a water mist mass of 1 g / m³ on the surface of the coated steel plate. 2 ~5g / m 2 The cooling rate is 10-20℃ / s, and the final temperature is 260-300℃; the temperature of the top turning roller is 150℃-210℃.

[0018] Furthermore, in step (4) of the present invention, the finishing process has a finishing elongation of 0.3% to 0.6%, a finishing roller roughness of 3.0 to 3.7 μm, and a peak density Pc value ≥ 90 particles / cm.

[0019] Furthermore, in step (4) of the present invention, the tension straightening elongation is 0.3 to 0.8%.

[0020] Furthermore, the process parameters of the cleaning section in step (4) of the present invention are: residual iron 0.1-0.5 mg / L, substrate reflectivity 85-95%, alkaline aqueous solution temperature 50-80℃, alkaline solution concentration 35-70 g / L, and conductivity 30-80 ms / cm.

[0021] The zinc-aluminum-magnesium coated steel prepared by the method of the present invention has a flatness of ≤2mm / 5m, a coating thickness of 5~30μm, and a coating hardness of 100HV~200HV.

[0022] The technical solution of this invention has the following beneficial technical effects:

[0023] (1) The low-temperature annealing process is conducive to the dispersion strengthening effect of nano-scale precipitated carbides and avoids the formation of coarse cementite. At the same time, in order to avoid the problem of insufficient zinc flow lines and zinc layer bonding caused by excessively low homogenization temperature, measures are taken to improve the surface cleanliness and roughness of cold-rolled substrate. Meanwhile, the zinc plating temperature and dew point temperature are precisely controlled, and segmented cooling after plating is adopted to avoid the occurrence of defects such as zinc flow lines and black lines during the cooling process, thereby improving the coating bonding and wear resistance.

[0024] (2) The addition of Fe and Ce elements to the zinc bath further improves the adhesion between the substrate and the coating and the corrosion resistance of the coating. The addition of Si helps to improve the wettability of the strip steel and the zinc bath and reduce the coefficient of friction of the coating.

[0025] (3) Low-temperature winding is beneficial to reduce the heat release of pearlite phase transformation and the softening caused by hot winding, thereby reducing the occurrence of flat winding. At the same time, it can also refine the grains and suppress the formation of coarse cementite.

[0026] The cold-plated galvanized steel for automotive brake mufflers provided by this invention, while meeting strength and flatness requirements, also exhibits excellent corrosion resistance and wear resistance in its zinc-aluminum-magnesium coating, solving the problems of insufficient corrosion resistance and easy wear in existing automotive brake muffler steels. The provided steel plate has a yield strength ≥660MPa, tensile strength ≥700MPa, elongation after fracture (A50) ≥5%, flatness ≤2mm / 5m, coating hardness 100HV~200HV, and coating thickness 5~30μm, exhibiting high flatness, good corrosion resistance, and wear resistance. Attached Figure Description

[0027] Figure 1The coating structure of the steel plate in Example 1 is shown.

[0028] Figure 2 The metallographic structure of the steel plate matrix in Example 1 is shown.

[0029] Figure 3 The results show the change in the friction coefficient of the steel plate coating with the number of friction cycles in Example 1. Detailed Implementation

[0030] The following will further explain and illustrate the method for manufacturing cold-based galvanized steel for automotive brake mufflers according to the present invention with reference to specific embodiments. However, this explanation and illustration do not constitute an undue limitation on the technical solution of the present invention.

[0031] Examples 1-6

[0032] The chemical composition of the steel used for cold-dip galvanized automotive brake mufflers in each embodiment is shown in Table 1.

[0033]

[0034] The production method of cold-based galvanized automotive brake muffler steel in each embodiment includes the following steps: (1) after smelting molten iron, it is refined and continuously cast to obtain a slab; (2) the slab is heated and then hot-rolled, coiled, straightened, pickled and cold-rolled to obtain a cold-based galvanized base material; (3) the cold-based galvanized base material is annealed, galvanized in a zinc pot, and then cooled in sections, finished, straightened and cleaned to obtain the final product.

[0035] The parameters for the heating, hot rolling, coiling, tension leveling, and pickling processes in step (2) are shown in Table 2, and the parameters for the cold rolling process are shown in Table 3.

[0036] The annealing process parameters in step (3) are shown in Table 4, and the galvanizing process parameters are shown in Table 5.

[0037] The parameters for the segmented cooling process in step (4) are shown in Table 6, the parameters for the finishing and straightening processes are shown in Table 7, and the process parameters for the cleaning section are shown in Table 8.

[0038] The mechanical properties and coating hardness of the cold-based galvanized automotive brake muffler steel prepared in each embodiment are shown in Table 9.

[0039] Neutral salt spray tests were conducted on the steel used for automotive brake mufflers in each embodiment. The procedure was as follows: Following the GB / T 10125-2012 standard, a salt spray corrosion test chamber (YWX / Q-750) was used, with continuous spraying for 24 hours. The corrosion solution was a 5% NaCl solution, the temperature was maintained at a constant 35°C, the chamber was placed at an angle of approximately 25°, and the salt spray deposition rate was 1.04 ml / h • 80 cm. 2The corrosion resistance results and coating hardness are shown in Table 10. Under neutral salt spray test conditions, the time for red rust to appear on the 5μm coating surface is ≥980h, and the time for red rust to appear on the cut surface is ≥490h, indicating that this material has good surface corrosion resistance and cut surface protection.

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]

[0049] Example 1: The coating structure of the steel plate is as follows Figure 1 As shown, the coating consists of Al-rich dendrites and Zn- and Zn-Mg-rich interdendritic second phases, with the interdendritic second phases distributed in a lamellar pattern. Example 1: Metallographic structure of the steel plate substrate as follows... Figure 2 As shown, the matrix structure is mainly composed of fine ferrite with a small amount of carbides.

[0050] According to GB / T 12444-2006 "Metallic Materials - Wear Test Methods - Sliding Wear Test of Test Rings and Specimens", the dynamic friction coefficient of the steel plate coating sample of Example 1 was tested under the test conditions of 1N force, 30mm stroke, and 300m / min speed. The results of the friction coefficient change with the number of friction cycles are as follows: Figure 3 As shown, the coefficient of friction increases slightly with the number of friction cycles, while the coefficient of dynamic friction of zinc-aluminum-magnesium coating is low and relatively stable.

Claims

1. A cold rolled galvanised automotive brake silencer sheet steel characterised in that, The chemical composition of the steel for the sound-absorbing sheet is as follows in wt%: C: 0.05-0.15%, Si: 0.01-0.05%, Mn: 0.3-0.8%, P: 0.01-0.03%, S: 0.005-0.012%, Al: 0.02-0.2%, Ti: 0.015-0.035%, and the balance of Fe and other impurities; The steel for the cold-base galvanized automobile brake sound-absorbing sheet is produced by the following steps: (1) after smelting, the molten iron is refined and continuously cast to obtain a slab; (2) the slab is heated, hot-rolled, coiled, straightened, pickled and cold-rolled to obtain a cold-base galvanized base material; (3) the cold-base galvanized base material is annealed and galvanized in a zinc pot, and then is subjected to step-by-step cooling, finishing, straightening and cleaning to obtain the steel for the cold-base galvanized automobile brake sound-absorbing sheet; In step (3), the cold-base galvanized base material is annealed by heating the galvanized base material at a rate of 0.5-5 ℃ / s to 500-600 ℃, soaking for 100-180 s, and then cooling at a rate of 10-20 ℃ / s to 430-460 ℃. In step (3), the galvanizing in the zinc pot is carried out at a grate dew point temperature of -20 to -10 ℃ and a zinc liquid temperature of 430-450 ℃, and the zinc liquid contains Al at a mass fraction of 1-5%, Mg at a mass fraction of 0.8-3%, Si at a mass fraction of 0.08-0.12%, Fe at a mass fraction of 0.01-0.05% and Ce at a mass fraction of 0.01-0.03%. The step (3) comprises first cooling and second cooling; the first cooling is gas cooling, the cooling rate is 10-25℃ / s, the end temperature is 290-320℃, and the solidification line of the molten coating is 3-9m away from the surface of the zinc liquid; the second cooling is water mist cooling, the water mist mass on the surface of the steel plate is 1g / m 2 ~5g / m 2 , the cooling rate is 10-20℃ / s, the end temperature is 260-300℃, and the temperature of the top deflection roller is 150-210℃.

2. A method of producing a steel for cold-rolled galvanized automotive brake silencer sheet according to claim 1, characterized in that, The method comprises the following steps: (1) after smelting, the molten iron is refined and continuously cast to obtain a slab; (2) the slab is heated, hot-rolled, coiled, straightened, pickled and cold-rolled to obtain a cold-base galvanized base material; (3) the cold-base galvanized base material is annealed and galvanized in a zinc pot, and then is subjected to step-by-step cooling, finishing, straightening and cleaning to obtain the steel for the cold-base galvanized automobile brake sound-absorbing sheet; In step (3), the cold-base galvanized base material is annealed by heating the galvanized base material at a rate of 0.5-5 ℃ / s to 500-600 ℃, soaking for 100-180 s, and then cooling at a rate of 10-20 ℃ / s to 430-460 ℃. In step (3), the galvanizing in the zinc pot is carried out at a grate dew point temperature of -20 to -10 ℃ and a zinc liquid temperature of 430-450 ℃, and the zinc liquid contains Al at a mass fraction of 1-5%, Mg at a mass fraction of 0.8-3%, Si at a mass fraction of 0.08-0.12%, Fe at a mass fraction of 0.01-0.05% and Ce at a mass fraction of 0.01-0.03%. The step (3) comprises first cooling and second cooling; the first cooling is gas cooling, the cooling rate is 10-25℃ / s, the end temperature is 290-320℃, and the solidification line of the molten coating is 3-9m away from the surface of the zinc liquid; the second cooling is water mist cooling, the water mist mass on the surface of the steel plate is 1g / m 2 ~5g / m 2 , the cooling rate is 10-20℃ / s, the end temperature is 260-300℃, and the temperature of the top deflection roller is 150-210℃.

3. A method of production of a cold reduced galvannealed automotive brake silencer sheet steel according to claim 2, characterized in that, In step (2), the heating is carried out at a temperature of 1200-1280 ℃ and for a soaking time of 180-240 min; and in the hot rolling, the finish rolling temperature is 870-940 ℃ and the coiling temperature is 450-540 ℃.

4. A method of producing a cold reduced galvannealed automotive brake silencer sheet steel according to claim 2, characterized in that, In step (2), the straightening is carried out at a straightening elongation of 0.8-2.0%, a bending roll insertion amount of 10-20 mm and a straightening roll insertion amount of 6-12 mm; and in the cold rolling, the cold rolling reduction is 50-90%, the IU value is ≤3, the F5 cold rolling machine roughness is 4.0-5.0 μm, the base material thickness is 0.3-1.8 mm, the base material reflectivity is ≥70% and the base material roughness is 0.7-1.0 μm.

5. A method of producing a cold reduced galvannealed automotive brake silencer sheet steel according to claim 2, characterized in that, The light finishing in step (3) has a light finishing elongation of 0.3-0.6%, a light finishing roller roughness of 3.0-3.7 μm, and a peak density Pc value of ≥90 / cm; the drawing and straightening has a drawing and straightening elongation of 0.3-0.8%.

6. A method of producing a cold reduced galvannealed automotive brake silencer sheet steel according to claim 2, characterized in that, The process parameters of the cleaning in step (3) are as follows: residual iron 0.1-0.5 mg / L, substrate reflectivity 85-95%, temperature of the alkaline aqueous solution 50-80 ℃, alkali concentration 35-70 g / L, and conductivity 30-80 ms / cm.

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