CN116219305A - A kind of Si-Cr system 480MPa grade hot-rolled steel plate for anti-wrinkle of bending pipe and its production method - Google Patents

Abstract

The invention provides a 480 MPa-grade hot-rolled steel plate for resisting bending wrinkling of Si-Cr and a production method thereof, wherein the hot-rolled steel plate comprises the following components in percentage by weight: 0.06 to 0.08 percent of C, 0.40 to 0.50 percent of Si, 1.20 to 1.30 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.005 percent of S, 0.40 to 0.50 percent of Cr, and Als:0.010 to 0.050 percent, and the balance of Fe and unavoidable impurities. The production method comprises the steps of molten iron desulfurization, converter smelting and combined converting, … …, continuous casting, slab heating, high-pressure water descaling, rough rolling, hot coil box coiling, finish rolling, laminar cooling, … … and warehousing. The invention realizes excellent welding performance and bending wrinkling resistance of the product through reasonable alloy composition and production process design, has simple production method, low cost and excellent comprehensive performance, and has good application prospect.

Description

A Si-Cr series 480MPa grade hot-rolled steel plate for anti-bending pipe wrinkling and its production method

Technical Field

The present invention relates to the technical field of hot-rolled plate and strip production, and in particular to a Si-Cr series 480MPa grade hot-rolled steel plate for anti-bending pipe wrinkling and a production method thereof.

Background Art

For thin-walled tubes (relative diameter greater than 30mm), CNC bending control technology is one of the inevitable trends in the development of tube bending technology towards advanced plastic processing technology. Thin-walled tube CNC precision bending technology can achieve high precision, high efficiency, high technology and lightweight requirements for tube plastic bending forming process, which is consistent with the development trend of automobile lightweighting and can be widely used in automobile chassis parts and Class B safety parts.

Patent document CN 105671427 A discloses a titanium chromium pickling plate and its preparation method, the chemical composition weight percentage of which is as follows: C 0.01% to 0.03%, Si 0.01% to 0.03%, Mn 0.14% to 0.30%, P 0.012% to 0.015%, S 0.003% to 0.005%, Cr 0.1% to 0.6%, Ti 0.012% to 0.023%, and the rest is Fe and unavoidable impurities. The product described in the patent can achieve a tensile strength of 270MPa to 350MPa, but its yield strength is too low and is not suitable for the bending forming process of thin-walled tubes.

The bending process of thin-walled tubes is prone to unstable wrinkling defects, resulting in substandard forming quality, which has become a key factor restricting the development of this technology. Whether thin-walled tubes wrinkle during bending is affected by many factors, among which the material is one of the important factors. The material affects the stress/strain effect of the bent tube under complex loading conditions and directly affects the wrinkle resistance of the part itself.

As shown in Figure 3, during the thin-walled tube bending process, the metal on the side far from the bending center is subjected to tensile stress in the tangential direction and produces elongation deformation, and the metal on the side close to the bending center is subjected to compressive stress in the tangential direction and produces compression deformation. The tangential stress changes from tensile stress on the outside of the bend to compressive stress on the inside along the cross section. Due to the poor stability of the tube wall thickness direction, when the plastic deformation energy T of the compression deformation zone of the shell inside the tube reaches the critical instability wrinkling energy U of the thin shell, under slight disturbance, the in-plane deformation will bifurcate to the outside of the plane, that is, instability wrinkling occurs.

These deformation characteristics during the bending process of thin-walled tubes make the bent tubes prone to problems such as outer cracking and inner wrinkling. In particular, as the die gap increases and the material hardening index decreases, the tangential compressive stress on the inner side of the tube wall will greatly increase, reducing the tube blank's ability to resist instability.

The main factors affecting the instability and wrinkling of thin-walled tube bending are as follows: ① Geometric factors: bending radius, relative tube diameter; ② Material factors: hardening index (or yield strength ratio), hardening coefficient (or strength limit); ③ Process factors: die gap, friction coefficient, bending speed, etc.

At present, domestic and foreign researchers have conducted a lot of research on the instability wrinkling of thin-walled tube bending forming process using experimental, theoretical analysis and finite element numerical simulation methods. Redd experimentally studied the instability wrinkling process of thin-walled tubes and found that the main reason for the instability wrinkling of thin-walled tubes was the "agitation" generated during the bending process of thin-walled tubes. Corona and Vaze used experimental verification methods to study the instability wrinkling phenomenon in the bending process of rectangular cross-section tubes and analyzed the collapse and wrinkling behavior of thin-walled tubes during the bending process. Zhang Jingwen et al. experimentally studied the influence of relative bending radius and relative tube wall thickness on the instability wrinkling of CNC bending forming and found that with the increase of relative bending radius and relative tube wall thickness, the wrinkling trend decreased. Kyriakids et al. used bifurcation theory to conduct relevant research on the instability wrinkling of tubes under pure bending conditions. The results showed that the theoretical prediction results were basically consistent with the experimental results. Li et al. established a quantitative prediction model for instability wrinkling in the CNC bending process of aluminum alloy thin-walled tubes based on the energy method, and combined with finite element simulation, explained the influence mechanism of geometric parameters and material parameters on bending instability wrinkling. Zhao et al. established a three-dimensional elastic-plastic finite element model of the CNC bending process of aluminum alloy thin-walled rectangular tubes based on the ABAQUS finite element analysis platform, and used this model to study the effect of gap on the instability wrinkling during the bending process of the bent tube. Fang et al. used the finite element simulation method to study the effect of friction factor and geometric parameters on the instability wrinkling of the CNC bending process of 21-6-9 high-strength stainless steel tubes. Li et al. used a numerical simulation method to study the effect of gap and friction on the instability wrinkling of the CNC bending process of the tube.

Most of the above studies are about the influence of process parameters and geometric parameters on the unstable wrinkling of tube bending forming, while there are relatively few studies on material parameters and low-alloy high-strength steels that resist tube bending wrinkling. Therefore, it is necessary to propose a hot-rolled high-strength steel for resisting tube bending wrinkling and a production method thereof to solve the above problems from the aspect of material parameters.

Summary of the invention

According to the above-mentioned lack of solution to resisting pipe bending wrinkling in terms of material parameters, a Si-Cr series 480MPa grade hot-rolled steel plate for resisting pipe bending wrinkling and a production method thereof are provided.

The technical problem to be solved by the present invention is that under the premise of ensuring that the performance requirements are met, the present invention mainly utilizes the proportion of the alloy components of the steel plate to achieve excellent welding performance and anti-bending wrinkling performance.

The technical means adopted by the present invention are as follows:

A Si-Cr 480MPa grade hot-rolled steel plate for anti-bending pipe wrinkling, characterized in that it is composed of the following components in weight percentage:

C 0.06%～0.08%, Si 0.40%～0.50%, Mn 1.20%～1.30%, P≤0.020%, S≤0.005%, Cr 0.40%～0.50%, Als: 0.010%～0.050%, and the balance is Fe and unavoidable impurities.

Further, it is composed of the following ingredients in weight percentage:

C 0.065%～0.075%, Si 0.41%～0.48%, Mn 1.21%～1.28%, P≤0.018%, S≤0.004%, Cr 0.41%～0.48%, Als: 0.017%～0.048%, and the balance is Fe and unavoidable impurities.

Further, it is composed of the following ingredients in weight percentage:

C 0.068%～0.072%, Si 0.45%～0.47%, Mn 1.21%～1.25%, P≤0.015%, S≤0.003%, Cr 0.45%～0.48%, Als: 0.027%～0.034%, and the balance is Fe and unavoidable impurities.

Furthermore, the hot-rolled steel plate has a thickness of 1.8 mm to 6.0 mm.

Furthermore, the hot-rolled steel plate has a thickness of 2.5 mm to 6.0 mm.

Furthermore, the hot-rolled steel plate has a thickness of 4.0 mm to 6.0 mm.

Furthermore, the hot-rolled steel plate for anti-bending pipe wrinkling has a yield strength of ≥355MPa, a tensile strength of ≥480MPa, an elongation after fracture of ≥28%, and a 180° bending test D=0a.

The present invention also discloses a production method of a Si-Cr 480MPa grade hot-rolled steel plate for anti-bending pipe wrinkling, which is characterized by comprising the following steps: preparing raw materials according to the composition of the above-mentioned Si-Cr 480MPa grade hot-rolled steel plate for anti-bending pipe wrinkling, and sequentially carrying out molten iron desulfurization → converter smelting composite blowing → deoxidation and alloying → Al wire feeding on a small platform behind the furnace → LF refining and heating → RH vacuum cycle degassing and refining → continuous casting → slab heating → high-pressure water descaling → rough rolling → hot coil box coiling → finishing rolling → laminar cooling → coiling → (welding head and tail → pickling → oiling → coiling →) storage.

Furthermore, the slab obtained by continuous casting is heated to 1220-1250°C for rough rolling. Depending on the thickness of the finished product, the continuous casting slab undergoes at least 3 rough rolling passes, with a deformation of ≥20% in each pass. Depending on the thickness of the finished product, the thickness of the intermediate slab varies, ranging from 36mm to 45mm.

Furthermore, after the intermediate billet is coiled in the hot coil box, it is shifted and uncoiled, and enters the finishing rolling area for finishing rolling. The finishing rolling adopts constant speed rolling, the finishing rolling inlet temperature is 1020~1070℃, and the final rolling temperature range is 860℃~900℃; the laminar cooling after finishing rolling adopts a segmented cooling method, the final temperature of the first cooling stage is 700℃~740℃, followed by air cooling for 3s~5s, and then rapid cooling to 520℃~560℃.

Compared with the prior art, the present invention utilizes the solid solution strengthening effect of Si and Mn and the strong hardenability of Cr to improve the strength of the material, and designs reasonable controlled rolling and controlled cooling process parameters to obtain an ideal microstructure, and finally obtains a hot-rolled steel plate or pickled steel plate product with anti-bending wrinkling ability.

The invention realizes excellent welding performance and anti-bending wrinkling performance of the product through reasonable alloy composition and production process design. At the same time, the product has a simple production method, low production cost, excellent comprehensive performance, and has a good application prospect.

Based on the above reasons, the present invention can be widely promoted in the field of hot-rolled strip production.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

FIG. 1 is a schematic diagram of the microstructure of a Si-Cr 480MPa grade hot-rolled steel plate for anti-bending pipe wrinkling in Example 3 of the present invention.

FIG. 2 is a schematic diagram of the limiting structure of comparative example 1 of a Si-Cr 480MPa grade hot-rolled steel plate for anti-bending pipe wrinkling of the present invention.

Figure 3 is a schematic diagram of the thin-walled tube bending process.

DETAILED DESCRIPTION

It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and/or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and/or combinations thereof.

Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, the numerical expressions and numerical values do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

The present invention provides a hot-rolled steel plate for anti-bending pipe wrinkling, which is composed of the following components in percentage by weight:

C 0.06%～0.08%, Si 0.40%～0.50%, Mn 1.20%～1.30%, P≤0.020%, S≤0.005%, Cr 0.40%～0.50%, Als: 0.010%～0.050%, and the balance is Fe and unavoidable impurities.

The production process of the present invention is: molten iron desulfurization → converter smelting composite blowing → deoxidation, alloying → Al wire feeding on a small platform behind the furnace → LF refining and heating → RH vacuum cycle degassing and refining → continuous casting → slab heating → high-pressure water descaling → rough rolling → hot coil box coiling → finishing rolling → laminar cooling → coiling → (welding head and tail → pickling → oiling → coiling →) storage.

Specifically, the slab obtained by continuous casting is heated to 1220-1250°C for heat preservation and rough rolling. According to the thickness of the finished product, the continuous casting slab undergoes 5 rough rolling passes, and the deformation amount of each pass must be ≥20%. According to the thickness of the finished product, the thickness of the intermediate slab is different: 36mm-45mm.

After rough rolling, the steel billet is then coiled in a hot coil box to ensure uniform temperature throughout the length of the billet; at the same time, the secondary iron oxide scale is removed to ensure a smooth surface of the billet.

After the intermediate billet is coiled by the hot coil box, it is shifted and uncoiled and enters the finishing rolling area for finishing rolling. The finishing rolling adopts constant speed rolling, the finishing rolling inlet temperature is 1020~1070℃, and the final rolling temperature range is 860℃~900℃; the laminar cooling after finishing rolling adopts a segmented cooling method, the final temperature of the first cooling stage is 700℃~740℃, followed by air cooling for 3s~5s, and then rapid cooling to 520℃~560℃.

After laminar cooling, the coils are taken up and put into storage; when the finished product is in the pickling state, the hot-rolled coils should be sent to the pickling production line, uncoiled, laser welded at the head and tail of the two steel coils, pickled, oiled, coiled and stored.

The specific implementation modes of the present invention are further described below in conjunction with embodiments, but the present invention is not limited to the scope of the embodiments.

Examples 1-4

Table 1 shows the chemical composition of the molten steel of the embodiment of the present invention, Table 2 shows the hot rolling process control values, and Table 3 shows the mechanical properties of the steel coil, wherein the yield strength (R _eL or R _p0.2 ), tensile strength (R _m ), and elongation (A%) of the steel coil are tested according to the method specified in GB/T228.1-2010. The microstructure of the obtained product is F+P+a small amount of B, and the grain size is 10.0 to 12.0.

Comparative Example

The production process of Comparative Examples 1 and 2 is the same as that of the embodiment, the chemical compositions thereof are shown in Table 1, the hot rolling process parameters are shown in Table 2, and the mechanical properties of the obtained hot rolled steel coils are shown in Table 3.

Table 1 Chemical compositions of the embodiments and comparative examples

Table 2 Hot rolling process control values of the embodiments and comparative examples

Table 3 Mechanical properties of steel coils obtained in the examples and comparative examples

In summary, as shown in Figures 1 and 2, the present invention utilizes the solid solution strengthening effect of Si and Mn and the strong hardenability of Cr, with a tensile strength of 480 MPa, to improve the strength of the material, and designs reasonable controlled rolling and controlled cooling process parameters to obtain an ideal microstructure, and finally obtains a hot-rolled steel plate or pickled steel plate product with anti-bending wrinkling ability.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. A480 MPa-grade hot rolled steel plate for resisting bending wrinkling of Si-Cr is characterized by comprising the following components in percentage by weight:

0.06 to 0.08 percent of C, 0.40 to 0.50 percent of Si, 1.20 to 1.30 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.005 percent of S, 0.40 to 0.50 percent of Cr, and Als:0.010 to 0.050 percent, and the balance of Fe and unavoidable impurities.

2. The Si-Cr 480 MPa-grade hot-rolled steel sheet for pipe bending wrinkling resistance according to claim 1, wherein the steel sheet comprises the following components in percentage by weight:

0.065-0.075% of C, 0.41-0.48% of Si, 1.21-1.28% of Mn, less than or equal to 0.018% of P, less than or equal to 0.004% of S, 0.41-0.48% of Cr, als:0.017 to 0.048 percent, and the balance of Fe and unavoidable impurities.

3. The Si-Cr 480 MPa-grade hot-rolled steel sheet for pipe bending wrinkling resistance according to claim 2, wherein the steel sheet comprises the following components in percentage by weight:

0.068 to 0.072 percent of C, 0.45 to 0.47 percent of Si, 1.21 to 1.25 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.003 percent of S, 0.45 to 0.48 percent of Cr and Als:0.027% -0.034%, and the balance of Fe and unavoidable impurities.

4. The hot-rolled steel sheet for 480 MPa-level bending resistance and wrinkling of si—cr system according to claim 1, wherein the thickness of the hot-rolled steel sheet is 1.8mm to 6.0mm.

5. The hot-rolled steel sheet for 480 MPa-level bending resistance and wrinkling of si—cr system according to claim 2, wherein the thickness of the hot-rolled steel sheet is 2.5mm to 6.0mm.

6. The hot-rolled steel sheet for bending and wrinkling resistance according to claim 3, wherein the thickness of said hot-rolled steel sheet is 4.0mm to 6.0mm.

7. The hot-rolled steel sheet for bending and wrinkling resistance according to claim 1, wherein said hot-rolled steel sheet for bending and wrinkling resistance has a yield strength of not less than 355MPa, a tensile strength of not less than 480MPa, an elongation after break of not less than 28%, and a 180 ° bending test d=0a.

8. A production method of a 480 MPa-grade hot rolled steel plate for resisting bending wrinkling of Si-Cr is characterized by comprising the following steps: the hot rolled steel sheet for 480 MPa-level bending and wrinkling resistance according to any one of claims 1 to 7, wherein the raw materials are prepared by sequentially carrying out molten iron desulfurization, converter smelting and combined converting, deoxidization, alloying, small-platform feeding Al wire after the converter, LF refining heating, RH vacuum circulation steam stripping refining, continuous casting, slab heating, high-pressure water descaling, rough rolling, hot rolling box coiling, finish rolling, laminar cooling, coiling, welding head and tail, pickling, oiling, coiling and warehousing.

9. The production method according to claim 8, characterized in that: heating a slab obtained by continuous casting to 1220-1250 ℃, carrying out heat preservation and rough rolling, carrying out at least 3 times of rough rolling on the continuous casting slab according to the thickness of a finished product, wherein the deformation of each time is more than or equal to 20%, and the thickness of an intermediate slab is between 36mm and 45mm according to the thickness of the finished product.

10. The production method according to claim 8, characterized in that: the intermediate billet is coiled by a hot coil box and then is shifted and uncoiled, enters a finish rolling area for finish rolling, the finish rolling adopts constant-speed rolling, the finish rolling inlet temperature is 1020-1070 ℃, and the finish rolling temperature range is 860-900 ℃; the laminar cooling after finish rolling adopts a sectional cooling mode, the final temperature of the first cooling is 700-740 ℃, then air cooling is carried out for 3-5 s, and then rapid cooling is carried out to 520-560 ℃.

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