A steel for an automobile filter housing and a method for manufacturing the same

Abstract

The application discloses a kind of automobile filter shell steel and its preparation method, belong to metallurgical technical field overcome the defect that automobile filter shell steel in prior art is easily produced " sand eye " in stamping process.A kind of automobile filter shell steel, chemical composition includes by mass percent: C:0.025~0.045%, Si:0.046~0.060%, Mn:0.15~0.25%, P:0.020~0.050%, S:≤0.0050%, Cr:0.16~0.35%, Mo:0.046~0.060%, Ln:0.006~0.012%, Al:0.015~0.065%, Nb:0.034~0.044, Ti:0.048~0.058%, O:≤0.0030%, N:≤0.0040%, the rest is iron element and inevitable impurity element;Ln / S=3.65~4.05, Ln / Al=0.39~0.55;Ln includes at least one of La, Ce, Pr.The application can significantly reduce the inclusion quantity and size of filter shell steel, reduce the production of " sand eye " in stamping process, improve the service life of filter shell.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of metallurgy, and particularly relates to a steel for an automobile filter shell and a preparation method thereof. BACKGROUND

[0002] The main function of the automobile filter shell is to protect the internal filter element and seal the filter element and oil body. The steel for the automobile filter shell is currently mainly low-wear and low-corrosion cold-rolled steel plate or steel strip, which generally has low strength, and the thickness specification is in the range of 0.8-1.5 mm, and is applied to deep drawing manufacturing of the filter shell. Therefore, the control requirement for inclusions of the filter shell steel is relatively high, and the number of inclusions needs to be reduced or the inclusions need to be refined to reduce the generation of "sand eye" defects after drawing.

[0003] However, the inclusions of the steel for the automobile filter shell produced by the conventional component system are relatively large in size and relatively large in number, and the "sand eye" is easily generated in the process of preparing the automobile filter shell. SUMMARY

[0004] Therefore, the technical problem to be solved by the present application is to overcome the "sand eye" defect easily generated in the drawing process of the automobile filter shell steel in the prior art, so as to provide a steel for an automobile filter shell and a preparation method thereof.

[0005] To this end, the present application provides the following technical solutions.

[0006] A steel for an automobile filter shell, the chemical components of which include, in terms of mass percentage:

[0007] C: 0.025-0.045%, Si: 0.046-0.060%, Mn: 0.15-0.25%, P: 0.020-0.050%, S: ≤0.0050%, Cr: 0.16-0.35%, Mo: 0.046-0.060%, Ln: 0.006-0.012%, Al: 0.015-0.065%, Nb: 0.034-0.044, Ti: 0.048-0.058%, O: ≤0.0030%, N: ≤0.0040%, and the rest is iron elements and inevitable impurity elements; Ln / S = 3.65-4.05, and Ln / Al = 0.39-0.55.

[0008] Ln includes at least one of La, Ce and Pr.

[0009] C is an important element for improving the strength, hardness and wear resistance of the steel material, but excessive C content will reduce the plasticity of the steel and affect the forming performance of the steel. In order to make the product have good performance matching, the C content in the present application is controlled in the range of 0.025-0.045%.

[0010] Si is a ferrite forming element, which is beneficial to the hot rolling low temperature rolling production of the steel, can improve the strength of the solid solution in the steel, and is more significant to improve the tensile strength of the steel. Moreover, when Si is combined with Cr, Mo, Ln and other elements, the corrosion resistance of the steel can be improved, when the content of Si is relatively high, it is beneficial to refine the corrosion product alpha-FeOOH, and promote the steel surface to form a dense silicon-rich protective rust layer, so as to improve the corrosion resistance, but too high will form strip-shaped aluminum-silicon inclusions, and also aggravate the surface oxidation scale of the steel. Therefore, the content of Si in the application is controlled to be 0.046-0.060%.

[0011] Mn is one of the important solid solution strengthening elements in the steel, but too high content of Mn will not only reduce the elongation, but also damage the toughness of the steel, and also reduce the corrosion resistance of the steel, and increase the manufacturing cost. Therefore, the content of Mn in the application is controlled to be 0.15-0.25%.

[0012] P can improve the corrosion resistance of the steel, and has a strong solid solution strengthening effect, but P is easy to segregate at the grain boundary to reduce the toughness of the steel. Therefore, the content of P in the application is controlled to be 0.020-0.050%.

[0013] S is a harmful element in the steel, which is easy to form long strip-shaped sulfide inclusions to deteriorate the plasticity and toughness of the steel and the corrosion resistance, is easy to combine with Ti to generate Ti4C2S2, reduces the content of Ti which has a strengthening effect, and thus affects the strengthening effect of the micro-alloying element Ti. Therefore, the content of S in the application is controlled to be ≤0.0050%.

[0014] Cr is a ferrite forming element, which is beneficial to the hot rolling low temperature rolling production of the steel. At the same time, Cr can significantly improve the wear resistance and corrosion resistance of the steel, and the addition of Cr is beneficial to form a fine and dense inner layer corrosion product film alpha-FeOOH on the surface of the steel, which can effectively inhibit the corrosive ions, but too high content of Cr will reduce the plasticity and toughness of the steel, therefore, the content of Cr in the application is controlled to be 0.16-0.35%.

[0015] Mo can greatly reduce the corrosion rate of the steel and improve the corrosion resistance of the steel. At the same time, Mo is a ferrite solid solution strengthening element, which can improve the strength, hardness and wear resistance of the steel, and also can reduce the non-uniformity of the structure in the hot working process, and improve the thermal stability of the micro-alloyed carbonitride. Therefore, the content of Mo in the application is controlled to be 0.046-0.060%.

[0016] Al is an important deoxidizing element in the steel, and can form AlN particles with N in the steel to refine the grain size, at the same time, Als fixes the free N in the steel, and increases the content of effective Ti in the steel, but excessive Al will form a large number of dispersed needle-shaped Al2O3 inclusions in the steel, which reduces the toughness and forming performance of the steel, therefore, the content of Al in the application is controlled to be 0.015-0.065%.

[0017] Ln can improve the comprehensive mechanical properties of steel by purifying steel, modifying inclusions, and refining grains. It can also significantly improve the wear resistance and corrosion resistance of steel. However, if the Ln content is too high during the heat treatment of steel, solid solution Ln desolvation is likely to occur, making the grain boundaries brittle and deteriorating the performance of the steel. Therefore, the Ln content in the present invention is controlled to 0.006-0.012%.

[0018] In order to ensure the modification effect of reducing, refining and spheroidizing inclusions, the chemical composition of the steel of the present invention must meet the ranges of Ln / S and Ln / Al of 3.65-4.05 and 0.39-0.55 respectively, and the modification effect becomes better with the increase of Ln / S and Ln / Al values.

[0019] Niobium (Nb) is a strong carbonitride-forming element, contributing to precipitation strengthening and grain refinement during controlled rolling and controlled cooling, improving the strength, hardness, and wear resistance of steel. Niobium also forms stable compounds with other elements in the steel (such as Fe and N) on the surface, further enhancing the steel's wear and corrosion resistance. However, excessive niobium levels can also easily form low-melting-point eutectics with elements like iron and carbon, increasing the metal's tendency to crack in welds. Therefore, the present invention limits the Nb content to 0.034% to 0.044%.

[0020] Ti is a strong carbonitride-forming element, which can promote precipitation strengthening and grain refinement, reduce anisotropy in steel strip, and improve deep-drawability. However, excessive Ti content increases the size and quantity of TiN, a secondary precipitate, thereby negatively impacting the deep-drawability of the steel sheet. Therefore, the present invention limits the Ti content to 0.048-0.058%.

[0021] O and N have a strong affinity with titanium. O combines with Ti in molten steel to form TiO2, and N combines with Ti to form coarse TiN particles, thereby reducing the titanium content in the molten steel that has a strengthening effect and reducing the strengthening effect of titanium. At the same time, a high O content easily forms string-like oxide inclusions, which reduces the formability of the steel. Therefore, the O content in the present invention is controlled to ≤0.0030% and the N content is controlled to ≤0.0040%.

[0022] Ln includes at least one of La, Ce, and Pr.

[0023] Furthermore, the thickness of the steel used for the automobile filter housing is 0.50 to 1.20 mm.

[0024] In a second aspect, the method for preparing steel for automobile filter housing of the present invention comprises continuous casting → heating of ingot → rough rolling → finishing rolling → laminar cooling → acid continuous rolling → continuous annealing.

[0025] Further, the casting speed is 1.3-1.5 m / min, the slab thickness is 200-220 mm, the slab width is ≤1300 mm, and the slab length is 9600-11000 mm.

[0026] Further, the slab heating is hot charging of the slab into a furnace, the charging temperature is ≥600℃, the heating time is ≥155 min, and the discharging temperature is 1125-1145℃.

[0027] Further, the rough rolling exit temperature is 950-990℃, the intermediate slab thickness is 35-40 mm;

[0028] the finish rolling entry temperature is 870-910℃, the finish rolling exit temperature is 770-810℃, and the finish rolling total reduction is 90.5-92.0%.

[0029] Further, the laminar cooling exit temperature is 600-640℃.

[0030] Further, the pickling and cold rolling include pickling and cold rolling;

[0031] the steel temperature before pickling is <45℃, the acid concentration is 30-200 g / L, and the acid temperature is 70-80℃;

[0032] the pickling is followed by rinsing to remove the acid, the rinsing temperature is 53-63℃, the outlet tank rinsing pH value is >6.0, and the outlet tank rinsing conductivity is ≤30 μS / cm.

[0033] the cold rolling total reduction is 66.5-82.5%.

[0034] Further, the continuous annealing includes: the steel strip obtained by pickling and cold rolling is subjected to an annealing section, a controlled cooling section, and a skin pass section.

[0035] Further, at least one of the following conditions is met:

[0036] (1) the steel strip speed is 120-160 m / min;

[0037] (2) the annealing section includes a heating section and a holding section in sequence;

[0038] the heating rate of the heating section is 2.55-3.70℃ / s, and the holding section temperature is 800-840℃;

[0039] (3) the controlled cooling section includes a slow cooling section, a fast cooling section, and an overaging section in sequence;

[0040] the slow cooling rate of the slow cooling section is 3.00-5.50℃ / s, the fast cooling rate of the fast cooling section is 28.55-38.55℃ / s, and the overaging rate of the overaging section is 0.10-0.15℃ / s;

[0041] (4) the flattening extension rate of the flattening section is 1.4-1.8%, and the flattening tension is 70-75 kN.

[0042] Optionally, the flattening section adopts single rack for flattening, and the working roll of the flattening machine adopts electric spark roughening roll, the roll surface roughness Ra is 1.0-1.5 microns, and the roll surface roughness peak count Rpc is 70-110 cm -1 .

[0043] Further, the rough rolling is R1 and R2 two rack rolling, R1 adopts 1 pass rolling, and R2 adopts 5 pass rolling.

[0044] After pickling, the pickling liquid is removed by using a rinsing liquid: the rinsing liquid temperature is 53-63 DEG C, the outlet tank rinsing liquid pH value is > 6.0, and the outlet tank rinsing liquid conductivity is <= 30 muS / cm.

[0045] The technical scheme of the present application has the following advantages:

[0046] 1. The chemical composition of the automobile filter shell steel according to the present application includes, in terms of mass percentage: C: 0.025-0.045%, Si: 0.046-0.060%, Mn: 0.15-0.25%, P: 0.020-0.050%, S: <=0.0050%, Cr: 0.16-0.35%, Mo: 0.046-0.060%, Ln: 0.006-0.012%, Al: 0.015-0.065%, Nb: 0.034-0.044, Ti: 0.048-0.058%, O: <=0.0030%, N: <=0.0040%, and the rest is iron element and inevitable impurity element; Ln / S = 3.65-4.05, Ln / Al = 0.39-0.55; Ln includes at least one of La, Ce and Pr.

[0047] The automobile filter shell steel according to the present application can reduce the content of harmful elements in the steel and segregation at the grain boundary by adding appropriate amount of Ln rare earth element, has the effect of purifying the steel; the shape, size, distribution, composition, structure and type of inclusions in the filter shell steel can be changed by adding appropriate amount of Ln rare earth element, the inclusions are reduced, refined and spheroidized, so that the comprehensive mechanical properties of the filter shell steel are improved and the "sand eye" defect in the punching process is reduced. The automobile filter shell steel according to the present application adopts C-Mn composition system and is micro-alloyed with Cr, Mo, Ti and Ln, which can significantly reduce the number and size of inclusions in the filter shell steel, reduce the generation of "sand eye" in the punching process, and improve the service life of the filter shell.

[0048] 2. The preparation method of the automobile filter shell steel according to the application, wherein the rough rolling outlet temperature is 950-990 DEG C, the intermediate blank thickness is 35-40 mm, the finish rolling inlet temperature is 870-910 DEG C, the finish rolling outlet temperature is 770-810 DEG C, and the finish rolling total reduction is 90.5-92.0%.

[0049] The hot rolling process adopts a suitable low-temperature process: low-temperature heating + low-temperature rolling, which can not only greatly reduce the consumption of heating energy, but also reduce the oxidation burning loss caused by high-temperature production, improve the yield and production efficiency; the low-temperature system can reduce the roll temperature rise, reduce the fatigue cracking and fracture caused by thermal stress, and reduce the roll consumption; the low-temperature system can reduce the generation of secondary oxide scale, improve the surface quality of the hot-rolled product, and improve the pickling effect and efficiency; the base material produced by the low-temperature process has lower strength, which can effectively reduce the subsequent cold continuous rolling load, save energy and reduce consumption; and the cold rolling deformation can be appropriately increased to improve the production efficiency; the cold rolling annealing product produced by the low-temperature process has good anisotropy and excellent forming performance. It can be seen that the low-temperature production process can realize energy saving and consumption reduction, green environmental protection, cost reduction and efficiency increase in the production of automobile filter shell steel, and belongs to the field of low-energy-consumption green environmental protection manufacturing process.

[0050] The low-temperature process defined in the application can avoid the problem of increased hot rolling mill rolling load caused by too low hot rolling process temperature, reduce energy and roll consumption, and reduce the occurrence of production accidents such as rolling load overload.

[0051] 3. The automobile filter shell steel according to the application combines the composition with the hot rolling low-temperature process, and through the comprehensive control of process sizes such as the thickness, width and length of the casting blank, the thickness of the intermediate blank, the total reduction of the hot rolling finish rolling and the total reduction of the cold continuous rolling, the rolling load and roll consumption can be further reduced.

[0052] Through the "Ln-Cr-Mo-Nb-Ti micro-alloying + process temperature and size control", the strength, wear resistance and corrosion resistance of the automobile filter shell steel can be significantly improved, the service life of the filter shell is increased, and high-strength thinning and light weight are realized. BRIEF DESCRIPTION OF DRAWINGS

[0053] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0054] Figure 1 The metallographic morphology diagram of Example 1. DETAILED DESCRIPTION

[0055] The following examples are provided to better enable those skilled in the art to further understand the application and are not intended to limit the scope of the application. The content and scope of the application are not limited to the best mode for carrying out the application, and any product that is the same or similar to the present application obtained by the disclosure of the present application or by combining the present application with other prior art features falls within the scope of the present application.

[0056] The specific experimental steps or conditions not mentioned in the examples can be carried out according to the conventional experimental steps described in the literature in the art or the operation or conditions. The reagents or instruments used are not specified by the manufacturer, and are conventional reagent products that can be obtained by purchase.

[0057] Example 1

[0058] The present embodiment provides a steel for an automobile filter housing, which has the following chemical composition and mass percentage: C: 0.027%, Si: 0.058%, Mn: 0.19%, P: 0.023%, S: 0.0019%, Cr: 0.27%, Mo: 0.053%, Ln = La + Pr: 0.007% (La: 0.002%, Pr: 0.005%), Al: 0.018%, Nb: 0.035%, Ti: 0.051%, O: 0.0015%, N: 0.0009%, and the balance of Fe and unavoidable impurities, as shown in Table 1.

[0059] The production process flow is: continuous casting → billet heating → rough rolling → finish rolling → laminar cooling → acid continuous rolling → continuous annealing, which specifically includes the following steps:

[0060] 1. Smelting: smelting the raw materials into the above-mentioned component molten steel.

[0061] 2. Continuous casting: continuous casting speed 1.5 m / min, billet thickness 200 mm, billet width 1250 mm, billet length 9800 mm.

[0062] 3. Billet heating → rough rolling → finish rolling: the billet is hot charged into the furnace, the charging temperature is 813℃, the heating time is 161 min, the discharge temperature is 1135℃, the hot rolling rough rolling adopts two-stand R1 + R2 = 1 + 5 mode, that is, R1 adopts 1-pass rolling, R2 adopts 5-pass rolling, the rough rolling R2 outlet temperature is 965℃, the intermediate billet thickness is 35mm, the finish rolling inlet temperature is 883℃, the finish rolling outlet temperature is 795℃, the finish rolling total reduction is 91.9%, and the laminar cooling outlet temperature is 625℃.

[0063] 4. Pickling: the temperature of the steel before pickling is <45℃, the pickling medium is a hydrochloric acid solution with a concentration of 30-200 g / L, and the temperature of the hydrochloric acid solution is 80℃; after pickling, a rinsing liquid is used to remove the hydrochloric acid solution on the surface of the steel, the temperature of the rinsing liquid is 59℃, the pH value of the rinsing liquid at the outlet tank is >6.0, the electrical conductivity of the rinsing liquid at the outlet tank is ≤30 μS / cm, and the total reduction of the cold continuous rolling is 82.5%.

[0064] 5. Annealing and temper rolling: the steel strip obtained through pickling is sent into an annealing and temper rolling furnace, and is treated through an annealing section, a controlled cooling section, and a temper rolling section. The length of the heating section of the annealing and temper rolling furnace is 610 m, the length of the holding section is 210 m, the length of the slow cooling section is 78 m, the length of the fast cooling section is 18 m, and the length of the overaging section is 750 m.

[0065] The temperature of the holding section of the annealing and temper rolling is 823℃, the speed of the steel strip is 153 m / min, the heating rate of the heating section is 3.43℃ / s, the slow cooling rate is 4.68℃ / s, the fast cooling rate is 36.83℃ / s, and the overaging rate is 0.14℃ / s.

[0066] The temper rolling section uses a single stand to perform temper rolling, the work roll of the temper rolling machine uses an electric spark roughened roll, the roughness Ra of the roll surface is 1.0-1.5 μm, the peak count Rpc of the roughness of the roll surface is 70-110 cm -1 , the temper rolling elongation is 1.4%, and the temper rolling tension is 73 kN.

[0067] The obtained automobile filter housing steel product has a thickness of 0.50 mm, and the mechanical properties, the surface, and the inclusions are shown in Tables 2 and 3.

[0068] Example 2

[0069] The present example provides an automobile filter housing steel, which has the following chemical components and mass percentages: C: 0.032%, Si: 0.055%, Mn: 0.18%, P: 0.031%, S: 0.023%, Cr: 0.28%, Mo: 0.054%, Ln=Ce: 0.009%, Al: 0.017%, Nb: 0.037%, Ti: 0.053%, O: 0.0019%, N: 0.0012%, and the balance being Fe and inevitable impurities, as shown in Table 1.

[0070] The production process thereof is: continuous casting → billet heating → rough rolling → finish rolling → laminar cooling → pickling → annealing and temper rolling, and specifically includes the following steps:

[0071] 1. Smelting: smelting the raw materials into the above-mentioned component molten steel.

[0072] 2. Continuous casting: the continuous casting pulling speed is 1.5 m / min, the thickness of the billet is 200 mm, the width of the billet is 1250 mm, and the length of the billet is 10000 mm.

[0073] 3. Billet heating → rough rolling → finish rolling: the billet is hot charged into the furnace, the charging temperature is 794°C, the heating time is 173 min, the discharging temperature is 1125°C, the hot rolling rough rolling adopts two stands R1+R2=1+5 mode, i.e. R1 adopts 1 pass rolling, R2 adopts 5 pass rolling, the rough rolling R2 exit temperature is 953°C, the intermediate billet thickness is 38 mm, the finish rolling entry temperature is 877°C, the finish rolling exit temperature is 806°C, the finish rolling total reduction is 91.7%, the laminar cooling exit temperature is 633°C.

[0074] 4. Pickling: the steel temperature before pickling is <45°C, the pickling medium is a hydrochloric acid solution with a concentration of 30-200 g / L, the hydrochloric acid solution temperature is 73°C; after pickling, a rinsing liquid is used to remove the hydrochloric acid solution on the surface of the steel, the rinsing liquid temperature is 63°C, the outlet tank rinsing liquid pH value is >6.0, the outlet tank rinsing liquid conductivity is ≤30 μS / cm, the cold rolling total reduction is 74.6%.

[0075] 5. Continuous annealing: the steel strip obtained after pickling is sent into a continuous annealing furnace for treatment through an annealing section, a controlled cooling section and a skin pass section. The continuous annealing furnace heating section length is 610 m, the holding section length is 210 m, the slow cooling section length is 78 m, the fast cooling section length is 18 m, and the overaging section length is 750 m.

[0076] The continuous annealing holding section temperature is 815°C, the steel strip speed is 144 m / min, the heating rate of the heating section is 3.20°C / s, the slow cooling rate is 4.15°C / s, the fast cooling rate is 34.67°C / s, and the overaging rate is 0.13°C / s.

[0077] The skin pass section adopts a single stand for skin pass, the work roll of the skin pass mill adopts an electric spark roughened roll, the roll surface roughness Ra is 1.0-1.5 μm, the roll surface roughness peak count Rpc is 70-110 cm -1 , the skin pass elongation is 1.5%, and the skin pass tension is 72 kN.

[0078] The obtained automobile filter housing steel product thickness is 0.80 mm, the mechanical properties, surface and inclusion conditions are shown in Tables 2 and 3.

[0079] Example 3

[0080] The embodiment provides a kind of automobile filter housing steel, its chemical composition and mass percentage are as follows: C:0.037%, Si:0.054%, Mn:0.23%, P:0.026%, S:0.0020%, Cr:0.29%, Mo:0.057%, Ln=La+Ce+Pr:0.008% (La:0.002%, Ce:0.003%, Pr:0.003%), Al:0.020%, Nb:0.043%, Ti:0.057%, O:0.0011%, N:0.0008%, the balance is Fe and inevitable impurities, as shown in table 1.

[0081] Its production process is: continuous casting→slab heating→rough rolling→finish rolling→laminar cooling→acid continuous rolling→continuous annealing, and specifically includes the following steps:

[0082] 1. Smelting: smelt raw materials into the above-mentioned component molten steel.

[0083] 2. Continuous casting: continuous casting speed is 1.5 m / min, slab thickness is 220 mm, slab width is 1250 mm, and slab length is 11000 mm.

[0084] 3. Slab heating→rough rolling→finish rolling: slab is hot charged into furnace, charging temperature is 805 DEG C, heating time is 164 min, discharging temperature is 1133 DEG C, hot rolling rough rolling adopts two-machine-stand R1+R2=1+5 mode, that is, R1 adopts one-pass rolling, R2 adopts five-pass rolling, rough rolling R2 outlet temperature is 971 DEG C, intermediate slab thickness is 38 mm, finish rolling inlet temperature is 881 DEG C, finish rolling outlet temperature is 810 DEG C, finish rolling total reduction is 90.5%, and laminar cooling outlet temperature is 623 DEG C.

[0085] 4. Acid continuous rolling: steel temperature is less than 45 DEG C before pickling, pickling medium is hydrochloric acid solution with concentration of 30-200 g / L, hydrochloric acid solution temperature is 77 DEG C; after pickling, pickling solution is used to remove hydrochloric acid solution on the surface of steel, pickling solution temperature is 57 DEG C, outlet tank pickling solution pH value is greater than 6.0, outlet tank pickling solution conductivity is less than or equal to 30 mu S / cm, and cold continuous rolling total reduction is 66.7%.

[0086] 5. Continuous annealing: the steel strip obtained by acid continuous rolling is sent into continuous annealing furnace, and is treated through annealing section, controlled cooling section and flattening section. The length of heating section of continuous annealing furnace is 610 m, the length of holding section is 210 m, the length of slow cooling section is 78 m, the length of fast cooling section is 18 m, and the length of overaging section is 750 m.

[0087] The temperature of continuous annealing holding section is 820 DEG C, the speed of steel strip is 151 m / min, the heating rate of heating section is 3.37 DEG C / s, the slow cooling rate is 4.52 DEG C / s, the fast cooling rate is 36.35 DEG C / s, and the overaging rate is 0.13 DEG C / s.

[0088] The flattening section adopts single rack for flattening, and the working roll of the flattening machine adopts electric spark roughening roll, the roll surface roughness Ra is 1.0-1.5μm, and the roll surface roughness peak count Rpc is 70-110cm -1 , the flattening elongation is 1.6%, and the flattening tension is 75kN.

[0089] The obtained automobile filter shell steel product has a thickness of 1.20mm, and the mechanical properties, surface and inclusion conditions are shown in Tables 2 and 3.

[0090] Example 4

[0091] The example provides an automobile filter shell steel, and the chemical components of the automobile filter shell steel are as follows in terms of mass percentage: C: 0.0041%, Si: 0.057%, Mn: 0.17%, P: 0.033%, S: 0.0025%, Cr: 0.28%, Mo: 0.058%, Ln=Ce+Pr: 0.010% (Ce: 0.004%, Pr: 0.006%), Al: 0.025%, Nb: 0.041%, Ti: 0.055%, O: 0.0017%, N: 0.0015%, and the balance is Fe and inevitable impurities, as shown in Table 1.

[0092] The production process is basically the same as that of Example 2, except that the hot rolling temperature control is different, that is, high-temperature austenite zone rolling, and the specific key process parameters are as follows: casting blank discharge temperature 1220℃, rough rolling R2 outlet temperature 1053℃, finishing rolling outlet temperature 885℃, and laminar cooling outlet temperature 689℃.

[0093] Comparative Example 1

[0094] The comparative example provides an automobile filter shell steel, and no Ln element is added, and the chemical components and mass percentage of the automobile filter shell steel are as follows: C: 0.0038%, Si: 0.053%, Mn: 0.16%, P: 0.025%, S: 0.0020%, Cr: 0.30%, Mo: 0.055%, Al: 0.023%, Nb: 0.039%, Ti: 0.054%, O: 0.0013%, N: 0.0011%, and the balance is Fe and inevitable impurities, as shown in Table 1.

[0095] The production process is basically the same as that of Example 2.

[0096] Table 1 Composition of steel of example and comparative example (wt%)

[0097]

[0098] Table 1 Composition of steel of example and comparative example (wt%)

[0099]

[0100] Table 2 Inclusion situation of each example and comparative steel

[0101]

[0102] From Table 2, the average size of inclusions of the automobile filter housing steel provided by Comparative Example 1 is 2.0 μm (not within the range of ≤1.5 μm), the density of inclusions with size ≥5.0 μm is 2.3 pieces / mm 2 (not within the range of ≤0.04 pieces / mm 2 ), and the density of inclusions with size ≥1.0 μm is 27 pieces / mm 2 (not within the range of ≤20 pieces / mm 2 ). The inclusion control level is low, and the "sand eye" defect is prone to occur in the punching process, and the forming performance is poor.

[0103] The number and size of inclusions of Examples 1-4 are significantly reduced compared with Comparative Example 1, and the number and size of inclusions of the automobile filter housing steel can be significantly reduced by using the composition system of the present application, thereby reducing the "sand eye" defect in the punching process and improving the service life of the automobile filter housing.

[0104] Yield strength, tensile strength and elongation A 80 The test was carried out according to GB / T 228.1, the work hardening index n value was tested according to GB / T 5028, the plastic strain ratio r and the anisotropy |Δr| were tested according to GB / T 5027, and the hardness HR30T was tested according to GB / T 230.1. The test results are shown in Table 3.

[0105] Table 3 Mechanical properties and surface situation of each example and comparative steel

[0106]

[0107]

[0108] From Table 3, the elongation A 80 of the automobile filter housing steel provided by Comparative Example 1 is 37, not within the range of ≥40; the work hardening index n value is 0.13, not within the range of ≥0.195; the plastic strain ratio r value is 0.95, not within the range of ≥1.95; and the planar anisotropy index |Δr| is 0.32, not within the range of ≤0.15. The forming performance is poor. The hardness HR30T is 64, not within the range of 71.5-77.5, and the wear resistance is poor.

[0109] The elongation A 80For 31, not in the range of ≥40; work hardening index n value is 0.17, not in the range of ≥0.195; plastic strain ratio r value is 1.03, not in the range of ≥1.95; planar anisotropy index |Δr| is 0.17, not in the range of ≤0.15. Using higher hot rolling temperature control process will result in its processing performance is poorer than that of examples 1-3.

[0110] Using the component system and production process of examples 1-3 of the present application, the environmentally friendly automobile filter shell steel with thickness of 0.5-1.20mm can be stably produced, and the product performance meets the yield strength R p0.2 : 280-360MPa, tensile strength R m : 490-590MPa, elongation A 80 : ≥40%, work hardening index n: ≥0.195, plastic strain ratio r: ≥1.95, planar anisotropy index |Δr|: ≤0.15, hardness HR30T: 71.5-77.5, plate surface roughness Ra: 0.2-0.7μm, plate surface roughness peak count Rpc: 40-90cm -1 , average size of inclusions: ≤1.5μm, density of inclusions with size ≥5.0μm: ≤0.04 / mm 2 , density of inclusions with size ≥1.0μm: ≤20 / mm 2 , metallographic structure is ferrite + cementite (as shown in Figure 1 ), the product forming and wear and corrosion resistance are good, the surface quality meets the customer's demand, realizes the low-temperature and low-load rolling production of wear and corrosion resistant rare earth filter shell steel, meets the demand of high strength thinning and light weight of vehicles, realizes the overall energy saving, cost reduction and consumption reduction, has considerable social and economic benefits, and belongs to the category of low energy consumption green manufacturing process.

[0111] Obviously, the above examples are only examples for clearly illustrating, but not limit the embodiments. For ordinary skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, all the embodiments need not and cannot be exhausted. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A steel for automobile filter housing, characterized in that: The chemical composition in mass percentage includes: C: 0.025~0.045%, Si: 0.046~0.060%, Mn: 0.15~0.25%, P: 0.020~0.050%, S: ≤0.0050%, Cr: 0.16~0.35%, Mo: 0.046~0.060%, Ln: 0.006~0.012%, Al: 0.015~0.065%, Nb: 0.034~0.044%, Ti: 0.048~0.058%, O: ≤0.0030%, N: ≤0.0040%, the rest are iron and unavoidable impurity elements; Ln / S=3.65~4.05, Ln / Al=0.39~0.55; Ln includes at least one of La, Ce, and Pr; The preparation method of the steel for automobile filter housing comprises continuous casting → heating of the ingot → rough rolling → finishing rolling → laminar cooling → acid continuous rolling → continuous annealing; The slab heating is to hot-charge the slab into the furnace, with the furnace temperature being ≥600°C, the heating time being ≥155min, and the furnace discharge temperature being 1125-1145°C; The rough rolling outlet temperature is 950-990°C, and the intermediate billet thickness is 35-40 mm; The finishing rolling inlet temperature is 870-910°C, the finishing rolling outlet temperature is 770-810°C, and the finishing rolling total reduction ratio is 90.5-92.0%; The laminar cooling outlet temperature is 600-640°C.

2. The steel for automobile filter housing according to claim 1, characterized in that: The thickness of the steel used for the automobile filter housing is 0.50-1.20 mm.

3. A method for preparing steel for automobile filter housing according to claim 1 or 2, characterized in that: Including continuous casting → slab heating → rough rolling → finishing rolling → laminar cooling → acid continuous rolling → continuous annealing; The slab heating is to hot-charge the slab into the furnace, with the furnace temperature being ≥600°C, the heating time being ≥155min, and the furnace discharge temperature being 1125-1145°C; The rough rolling outlet temperature is 950-990°C, and the intermediate billet thickness is 35-40 mm; The finishing rolling inlet temperature is 870-910°C, the finishing rolling outlet temperature is 770-810°C, and the finishing rolling total reduction ratio is 90.5-92.0%; The laminar cooling outlet temperature is 600-640°C.

4. The method for preparing steel for automobile filter housing according to claim 3, characterized in that: The continuous casting speed is 1.3-1.5 m / min, the thickness of the cast slab is 200-220 mm, the width of the cast slab is ≤1300 mm, and the length of the cast slab is 9600-11000 mm.

5. The method for preparing steel for automobile filter housing according to claim 3, characterized in that: Pickling continuous rolling includes pickling and cold continuous rolling; The steel temperature before pickling is less than 45℃, the pickling medium is acid solution with a concentration of 30~200g / L and a temperature of 70~80℃; The total reduction rate of cold rolling is 66.5~82.5%.

6. The method for preparing steel for automobile filter housing according to any one of claims 3 to 5, characterized in that: The continuous annealing process includes: subjecting the steel strip obtained by acid continuous rolling to an annealing section, a controlled cooling section and a flattening section for treatment.

7. The method for preparing steel for automobile filter housing according to claim 6, characterized in that: At least one of the following conditions is met: (1) Steel belt speed 120~160m / min; (2) The annealing section includes a heating section and a holding section in sequence; The heating rate of the heating section is 2.55~3.70℃ / s, and the temperature of the holding section is 800~840℃; (3) The controlled cooling section includes a slow cooling section, a fast cooling section, and an over-aging section in sequence; The slow cooling rate of the slow cooling section is 3.00~5.50℃ / s, the fast cooling rate of the fast cooling section is 28.55~38.55℃ / s, and the over-aging rate of the over-aging section is 0.10~0.15℃ / s; (4) The leveling elongation of the leveling section is 1.4~1.8%, and the leveling tension is 70~75kN.

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