Cold-rolled strip steel for filter element housing and manufacturing method thereof

Abstract

The present application belongs to the technical field of steel preparation, and in particular, relates to a cold-rolled strip steel for a filter element housing and a manufacturing method thereof; the chemical composition includes: C < 0.002 wt%, Si < 0.03 wt%, 0.10 wt% < Mn < 0.15 wt%, P < 0.010 wt%, S < 0.012 wt%, 0.03 wt% < Alt < 0.06 wt%, N < 0.003 wt%, 0.0025 wt% < B < 0.0045 wt%, and the rest is Fe and unavoidable impurities, and the metallographic structure of the steel is equiaxed polygonal ferrite; the present application adopts an ultra-low carbon component, fixes the interstitial solid solution N atoms in the steel by B, and controls the yield elongation value of the material after aging.

Description

Technical Field

[0001] The present application relates to the technical field of steel preparation, and in particular to a cold-rolled steel strip for a filter element housing and a manufacturing method thereof. Background Art

[0002] For lightweight considerations, filter housings for oil filters, air purifiers, etc. are usually made of ultra-thin cold-rolled strip steel through stamping. Since the drawing process of such products is relatively high, high requirements are placed on the deep drawing performance of the material. The deep drawing cold-rolled strip steel patents in the prior art mostly use ultra-low carbon component systems, with trace amounts of Ti and / or Nb elements added. The alloy production cost is relatively high, and the control level of the main product's forming performance and thickness specifications is only suitable for the processing and manufacturing of automotive and home appliance structural parts. Summary of the invention

[0003] The present application provides a cold-rolled strip steel for a filter element housing and a preparation method thereof, in order to solve the technical problems of the prior art in that the deep-drawn cold-rolled strip steel has poor forming performance and is limited in application due to large product thickness.

[0004] In a first aspect, the present application provides a cold-rolled steel strip for a filter element housing, wherein the steel comprises the following chemical components:

[0005] C<0.002wt%, Si<0.03wt%, 0.10wt%<Mn<0.15wt%, P<0.010wt%, S<0.012wt%, 0.03wt%<Alt<0.06wt%, N<0.003wt%, 0.0025wt%<B<0.0045wt%, and the rest are Fe and inevitable impurities; the metallographic structure of the steel is: equiaxed polygonal ferrite.

[0006] Optionally, the grain size of the equiaxed polygonal ferrite is 12.5 μm-15.0 μm.

[0007] Optionally, the performance parameters of the steel meet the following requirements: yield strength R el ≤180MPa, yield elongation YP-EL value<1.0%, elongation after fracture A 50 ≥35%, yield strength ratio R el / R m <0.60, plane plastic strain ratio Work hardening index n≥0.2, plane anisotropy index│△r│≤0.30.

[0008] In a second aspect, the present application provides a method for preparing a cold-rolled steel strip for a filter element housing, for realizing the preparation of the cold-rolled steel strip for a filter element housing according to any one embodiment of the first aspect, the method comprising:

[0009] Obtaining molten steel containing the chemical composition;

[0010] Under the conditions of set superheat degree of the tundish and billet drawing speed, the molten steel is continuously cast to obtain a billet;

[0011] Under the conditions of set steel tapping temperature, final rolling temperature and coiling temperature, hot rolling the ingot to obtain a hot rolled coil;

[0012] cold rolling the hot rolled coil under a set reduction rate to obtain a chilled coil;

[0013] Under a first set temperature condition, the cold hardened coil is subjected to a heating treatment, and when the temperature reaches a first temperature parameter, the heating is stopped;

[0014] Under a set insulation time condition, the chilled coil after the temperature increase treatment is subjected to insulation annealing treatment to obtain an annealed coil;

[0015] Under a second set temperature condition, performing an aging treatment on the annealed coil to obtain a first steel strip;

[0016] Under the set elongation condition, the first strip steel is flattened to obtain a cold-rolled strip steel for a filter element housing.

[0017] Optionally, the superheat of the tundish is 20°C-45°C, and the casting speed is 1.0m / min-1.2m / min.

[0018] Optionally, the steel tapping temperature is 1050°C-1100°C, the final rolling temperature is 780°C-800°C, and the coiling temperature is 640°C-680°C.

[0019] Optionally, the reduction ratio is 85%-90%.

[0020] Optionally, the first temperature parameter is 660°C-680°C, and the first insulation time is 60s-75s.

[0021] Optionally, the second set temperature is 350°C-330°C.

[0022] Optionally, the elongation is 1.4%-1.6%.

[0023] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0024] A cold-rolled strip steel for a filter element housing provided in an embodiment of the present application has the following chemical compositions, expressed in terms of mass fraction: C < 0.002 wt%, Si < 0.03 wt%, 0.10 wt% < Mn < 0.15 wt%, P < 0.010 wt%, S < 0.012 wt%, 0.03 wt% < Alt < 0.06 wt%, N < 0.003 wt%, 0.0025 wt% < B < 0.0045 wt%, and the remainder being Fe and unavoidable impurities. No microalloying elements are added to the composition, and the overall production cost is low. Ultra-low carbon components are used, and interstitial solid solution N atoms in the steel are fixed by B. The yield elongation YP-EL value of the product is < 1.0%, and the mechanical properties meet the requirements of terminal products. The product is particularly suitable for deep drawing processing and manufacturing of filter element housings such as oil filters and air purifiers. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0026] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0027] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0028] In the description of the specification of the present application, the terms "include", "including", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second", etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" means one or more, and "plurality" means two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0029] The technical solution of the embodiment of the present application is to solve the above technical problems, and the overall idea is as follows:

[0030] According to a typical embodiment of the present application, the present application provides a cold-rolled steel strip for a filter element housing, wherein the steel comprises the following chemical components:

[0031] C<0.002wt%, Si<0.03wt%, 0.10wt%<Mn<0.15wt%, P<0.010wt%, S<0.012wt%, 0.03wt%<Alt<0.06wt%, N<0.003wt%, 0.0025wt%<B<0.0045wt%, and the rest are Fe and inevitable impurities; the metallographic structure of the steel is: equiaxed polygonal ferrite.

[0032] In this embodiment, the more carbon atoms dissolved in the interstitial space in the steel, the higher the yield elongation YP-EL value during the stretching process of the material after baking, and the greater the probability of tensile strain marks appearing on the surface of the shell after stamping. It is generally believed that when the YP-EL value is lower than 1.4%, there are no obvious tensile strain marks on the surface after stamping. From the perspective of controlling the change in material aging properties and improving the surface quality of stamping parts, the lower the carbon content in the present invention, the better, the target range is <0.002% by weight, and the target value is controlled at 0.0015% by weight.

[0033] In this embodiment, solid-dissolved nitrogen in the steel is another important cause of material aging, and the coarse nitrides precipitated in the steel are not conducive to the improvement of the plasticity and toughness of the material. In the present invention, the lower the nitrogen content, the better, the target range is <0.003% by weight, and the target value is controlled at 0.002% by weight.

[0034] In this embodiment, the boron element can play a role in fixing nitrogen in the steel, that is, it combines with the nitrogen solid-solution in the interstitial space in the steel to form a BN phase and then precipitates out, which can effectively weaken the material aging hardening caused by the solid-solution nitrogen in the steel. The remaining boron after nitrogen fixation is solid-dissolved in the grain boundaries, which can inhibit the growth of grains and play a certain degree of fine grain strengthening role. However, if the boron content is too high, metallurgical defects such as cracks are easily formed during the continuous casting of the slab. In order to give full play to boron to improve material aging, refine grains, and avoid metallurgical defects such as cracks in the ingot, the present invention controls the content of B element in the range of 0.0025 wt%-0.0045 wt%, and the target value is controlled at 0.0035 wt%.

[0035] In this embodiment, manganese element in steel improves the strength of steel through solid solution strengthening and improves the hot working performance of steel. When the manganese content is lower than 0.1% by weight, the hot brittleness of the material increases and the basic strength cannot be achieved. When the manganese content is too high, the material strength exceeds the target range and the ductility decreases, which is not conducive to deep drawing processing. Taking comprehensive considerations, the present invention controls the Mn content in the range of 0.10-0.15% by weight, and the target value is controlled at 0.13% by weight.

[0036] In this embodiment, aluminum is an indispensable deoxidizer for steelmaking. When the aluminum content is too low, it cannot meet the need for complete deoxidation of molten steel. When the aluminum content is too high, the number of Al2O3 inclusions in the steel increases. The present invention limits the Alt content to a range of 0.03-0.06 weight %.

[0037] In this embodiment, silicon easily combines with oxygen to form an oxide layer on the surface of the steel strip, which reduces the corrosion resistance of the material. In order to improve the corrosion resistance of the material of the present invention, the silicon content is limited to the range of <0.03 weight%, and the target value is controlled at 0.01 weight%.

[0038] In this embodiment, phosphorus exists in the steel in a solid solution state, and the strength of the material can be improved by solid solution strengthening. However, when the phosphorus content exceeds 0.03 wt.%, it is easy to cause central segregation in the casting process. The present invention limits the phosphorus content to a range of <0.01 wt.%, and the target value is controlled at 0.006 wt.%.

[0039] In this embodiment, sulfur is generally considered to be an impurity element in steel. Sulfides in steel make the steel embrittled and reduce the corrosion resistance of the steel. The present invention controls the sulfur content within the range of <0.012 wt %, and the target value is controlled at 0.005 wt %.

[0040] In some embodiments, the grain size of the equiaxed polygonal ferrite is 12.5 μm-15.0 μm.

[0041] In some embodiments, the mechanical properties of the steel material meet the following requirements: yield strength R el ≤180MPa, yield elongation YP-EL value<1.0%, elongation after fracture A 50 ≥35%, yield strength ratio R el / R m <0.60, plane plastic strain ratio Work hardening index n≥0.2, plane anisotropy index│△r│≤0.30.

[0042] The above mechanical properties ensure that there is no obvious cracking or earing defects in the material during the shell forming process, and there is no obvious slip lines on the shell surface after stamping.

[0043] According to another typical embodiment of the present application, the present application provides a method for preparing a cold-rolled steel strip for a filter element housing, so as to realize the preparation of the cold-rolled steel strip for a filter element housing according to any one embodiment of the first aspect, the method comprising:

[0044] Obtaining molten steel containing the chemical composition;

[0045] Under the conditions of set superheat degree of the tundish and billet drawing speed, the molten steel is continuously cast to obtain a billet;

[0046] Under the conditions of set steel tapping temperature, final rolling temperature and coiling temperature, hot rolling the ingot to obtain a hot rolled coil;

[0047] cold rolling the hot rolled coil under a set reduction rate to obtain a chilled coil;

[0048] Under a first set temperature condition, the cold hardened coil is subjected to a heating treatment, and when the temperature reaches a first temperature parameter, the heating is stopped;

[0049] Under a set insulation time condition, the chilled coil after the temperature increase treatment is subjected to insulation annealing treatment to obtain an annealed coil;

[0050] Under a second set temperature condition, performing an aging treatment on the annealed coil to obtain a first steel strip;

[0051] Under the set elongation condition, the first strip steel is flattened to obtain a cold-rolled strip steel for a filter element housing.

[0052] In this embodiment, the cold rolling process adopts an ultra-high rolling ratio, specifically controlling the total cold rolling reduction rate to 85 wt%-90 wt%. The ultra-high rolling ratio is used to further improve the cold-rolled γ fiber texture ( <111> / / ND) strength, promoting the formation of strong {111} surface texture of the material in the subsequent retreat process, and further improving the material plane plastic strain ratio value.

[0053] In this embodiment, on the basis of the chemical composition, the processing technology determines the microstructure of the material, which in turn affects its mechanical properties. In the hot rolling process, low-temperature equiaxed polygonal ferrite rolling is adopted, in the cold rolling process, ultra-high pressure rolling ratio is adopted, in the annealing process, continuous annealing is adopted, the soaking temperature is controlled in a relatively low temperature range, and in the flattening process, double-frame flattening is adopted to control the total elongation in a reasonable range. Through the above key processes, the microstructure of the material is improved to achieve its target mechanical properties.

[0054] In some embodiments, the superheat of the tundish is 20°C-45°C, and the casting speed is 1.0m / min-1.2m / min.

[0055] In this embodiment, the above parameter control can ensure that the inclusions are fully floated and removed, thereby preventing large-sized inclusions formed during the continuous casting process from causing cracking of the shell material during the stamping process.

[0056] In some embodiments, the slab tapping temperature is 1050°C-1100°C; the final rolling temperature is 780°C-800°C; and the coiling temperature is 640°C-680°C.

[0057] In this embodiment, the present invention controls the slab tapping temperature to 1050-1100°C to avoid the second phase particles from dissolving back during the heating process and promote the formation of coarse and sparse second phase particles in the steel. The final rolling temperature is controlled to 780-800°C to ensure that the rolling is carried out in the equiaxed polygonal ferrite single phase region, and the coiling temperature is controlled to 640-680°C to ensure that the material completes sufficient recrystallization during the coiling process.

[0058] In some embodiments, the reduction ratio is 85%-90%.

[0059] In this embodiment, when the cold rolling reduction rate is lower than 85 weight %, the γ fiber texture strength in the ultra-thin cold-hardened strip cannot be significantly improved. When the cold rolling reduction rate is greater than 90 weight %, the material is severely work-hardened, the rolling load of the rolling mill increases, and the difficulty of cold rolling production is increased.

[0060] In some embodiments, the first temperature parameter is 660° C.-680° C., and the first insulation time is 60s-75s.

[0061] In this embodiment, the annealing temperature and time have an important influence on the microstructure and formability of the cold-rolled stamping steel strip. If the annealing temperature is too low and the time is too short, the material cannot fully recover and recrystallize, and the residual cold hard fiber structure leads to low elongation and poor formability. If the annealing temperature is too high and the time is too long, the annealing grains grow excessively, and the {111} texture is fully developed, but after annealing, the {111} <110> 、{111} <112> With {112} <110> The difference in texture strength increases, which is not conducive to reducing the Δr value of the material. In order to ensure that the material undergoes complete recrystallization and obtains good planar anisotropy, the present invention controls the annealing soaking temperature at 660-680°C.

[0062] In some embodiments, the elongation is 1.4%-1.6%.

[0063] In this embodiment, flattening is the last production process of the material of the present invention, and its main purpose is to eliminate the yield platform of the strip steel and improve the strip steel shape. If the flattening elongation is too low, the material yield platform is too long, and tensile strain marks are likely to appear after stamping. If the flattening elongation is too high, the material is prone to over-extension during the flattening process. In order to improve the mechanical properties of the material and improve the strip steel shape, the present invention controls the elongation during flattening within the range of 1.4-1.6%.

[0064] In this embodiment, the hot rolling process adopts an equiaxed polygonal ferrite rolling process. On the one hand, it avoids the problem of poor transverse structural uniformity caused by the edge of the strip entering the two-phase region due to the large temperature drop in the process of austenite rolling of extremely thin cold-rolled strip steel. On the other hand, by forming strong α fiber texture and γ fiber texture in the hot rolling process, the formation of {111} surface texture in the cold rolling annealing process is promoted, thereby improving the material plane plastic strain ratio. value.

[0065] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0066] The cold-rolled steel strip for filter element housing and the preparation method thereof of the present application will be described in detail below in combination with embodiments, comparative examples and experimental data.

[0067] Examples 1-9 in Tables 1-3 are the main components, manufacturing processes and mechanical properties of the products obtained according to the implementation of the patent of the present invention, and comparative examples 1-9 are the main components, manufacturing processes and mechanical properties of the products obtained beyond the restricted elements of the patent of the present invention.

[0068] Table 1

[0069]

[0070] Table 2 Table 3

[0071]

[0072]

[0073] By comparing Comparative Example 1 and Examples 1-9 in the attached table, it can be seen that when the C content does not meet the range of <0.0020 weight % of the patent of the present invention, the yield elongation YP-EL value of the product is 1.5%, which does not meet the technical requirement of YP-EL <1.0% in the mechanical properties of the product of the patent of the present invention.

[0074] By comparing Comparative Example 2 with Examples 1-9 in the attached table, it can be seen that when the N content does not meet the range of <0.0030 weight % of the patented invention, the yield elongation YP-EL value of the product is 1.6%, which does not meet the technical requirement of YP-EL <1.0% in the mechanical properties of the product of the patented invention.

[0075] By comparing Comparative Example 3 and Examples 1-9 in the attached table, it can be seen that when the B content does not meet the range of 0.0025 wt%-0.0045 wt% of the patented invention, the product yield elongation YP-EL value is 1.5%, which does not meet the technical requirement of YP-EL<1.0% in the mechanical properties of the product of the patented invention.

[0076] By comparing Comparative Example 4 with Examples 1-9 in the attached table, it can be seen that when the hot rolling final rolling temperature does not meet the range of 780-800°C of the present invention, the product The value is 1.82, and the △r value is 0.32, which does not meet the mechanical properties of the patented product of the present invention. │△r│≤0.30 technical requirement.

[0077] By comparing Comparative Example 5 with Examples 1-9 in the attached table, it can be seen that when the hot rolling final rolling temperature does not meet the range of 780-800°C of the present invention, the product The value is 1.79, and the △r value is 0.34, which does not meet the technical requirements of r ≥ 2.0, │△r│ ≤ 0.30 in the mechanical properties of the patented product of the present invention.

[0078] By comparing Comparative Example 6 with Examples 1-9 in the attached table, it can be seen that when the continuous annealing temperature does not meet the range of 660-680°C of the present invention, the product R el / R mValue 0.81, A 50 Value 16.7%, The value is 0.74, and the value of │△r│ is 0.51, which does not meet the mechanical properties of the product of the present invention. el / R m <0.6,A 50 >35%, │△r│≤0.30 technical requirement.

[0079] By comparing Comparative Example 7 with Examples 1-9 in the attached table, it can be seen that when the continuous annealing temperature does not meet the range of 660-680°C in the patent of the present invention, the product │△r│ value reaches 0.31, which does not meet the technical requirement of │△r│≤0.30 in the mechanical properties of the product of the patent of the present invention.

[0080] By comparing Comparative Example 8 and Examples 1-9 in the attached table, it can be seen that when the total flattening elongation does not meet the range of 1.4%-1.6% of the patented invention, the product YP-EL value is 1.8%, which does not meet the technical requirement of YP-EL<1.0% in the mechanical properties of the patented product of the invention.

[0081] By comparing Comparative Example 9 and Examples 1-9 in the attached table, it can be seen that when the flat total elongation does not meet the range of 1.4%-1.6% of the patent of the present invention, the product Rel value is 182MPa, R el / R m Value 0.66 ， │△r│ value is 0.31, which does not meet the mechanical properties of the patented product of this invention Rel<180MPa, R el / R m <0.6,│△r│≤0.30 technical requirements.

[0082] In summary, the present invention mainly provides an ultra-thin cold-rolled strip steel with excellent forming performance and a manufacturing method thereof, wherein the product thickness is 0.16-0.30 mm, the yield strength Rel≤180 MPa, the yield elongation YP-EL value is less than 1.0%, and the elongation after fracture A 50 ≥35%, yield strength ratio R el / R m <0.60, plane plastic strain ratio Value ≥ 2.0, work hardening index n value ≥ 0.2, plane anisotropy index │△r│ ≤ 0.30, no cracking after stamping after painting and baking, low earing, no obvious tensile strain marks on the surface, which can better meet the stamping manufacturing of precision filter housings such as oil filters and air purifiers.

[0083] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing a cold-rolled steel strip for a filter element housing, characterized in that: The method comprises: Obtain molten steel; Under the conditions of set superheat degree of the tundish and billet drawing speed, the molten steel is continuously cast to obtain a billet; Under the conditions of set steel tapping temperature, final rolling temperature and coiling temperature, hot rolling the ingot to obtain a hot rolled coil; cold rolling the hot rolled coil under a set reduction rate to obtain a chilled coil; Under a first set temperature condition, the cold hardened coil is subjected to a heating treatment, and when the temperature reaches a first temperature parameter, the heating is stopped; Under a set insulation time condition, the chilled coil after the temperature increase treatment is subjected to insulation annealing treatment to obtain an annealed coil; Under a second set temperature condition, performing an aging treatment on the annealed coil to obtain a first steel strip; Under the set elongation condition, the first strip steel is flattened to obtain a cold-rolled strip steel for a filter element housing; The superheat of the tundish is 20℃-45℃, the billet drawing speed is 1.0 m / min-1.2m / min; the tapping temperature is 1050℃-1100℃, the final rolling temperature is 780℃-800℃, the coiling temperature is 640℃-680℃; the reduction ratio is 85%-90%; the first temperature parameter is 660℃-680℃, the set insulation time is 60s-75s; the second set temperature is 350℃-330℃; the elongation is 1.4%-1.6%; The cold-rolled steel strip for the filter housing comprises the following chemical components: C<0.002wt%, Si<0.03wt%, 0.10wt%<Mn<0.15wt%, P<0.010wt%, S<0.012wt%, 0.03wt%<Alt<0.06wt%, N<0.003wt%, 0.0025wt%<B<0.0045wt%, and the rest are Fe and inevitable impurities; the metallographic structure of the steel is: equiaxed polygonal ferrite, and the grain size of the equiaxed polygonal ferrite is 12.5μm-15.0μm.

2. The cold-rolled steel strip for filter element housing prepared by the preparation method according to claim 1, characterized in that: The performance parameters of the cold-rolled strip steel meet the following requirements: yield strength R el ≤180MPa, yield elongation YP-EL value<1.0%, elongation after fracture A 50 ≥35%, yield strength ratio R el / R m <0.60, plane plastic strain ratio r≥2.0, work hardening index n≥0.2, plane anisotropy index│△r│≤0.30.

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