Preparation method of low-cost Q355CRE hot-rolled H-shaped steel

Abstract

The invention discloses a low-cost Q355CRE hot-rolled H-shaped steel preparation method. Technical parameters controlled in a rolling process are as follows: 1) the heating temperature is 1200-1240 DEG C, and the total heating time is greater than or equal to 2 hours; 2) the initial rolling temperature is less than or equal to 1100 DEG C; 3) the finish rolling temperature is less than or equal to 860 DEG C; the H-shaped steel comprises the following chemical components in percentage by mass: 0.17%-0.21% of C, 0.45%-0.50% of Si, 1.30%-1.40% of Mn, less than or equal to 0.018% of P, less than or equal to 0.010% of S, more than or equal to 0.015% of Al, 0.0010%-0.0020% of RE and the balance of Fe and other trace impurity elements. The performance indexes meet the following technical requirements that the yield strength Rel is larger than or equal to 355 MPa, the tensile strength Rm is larger than or equal to 490 MPa, the ductility A is larger than or equal to 23%, the 0 DEG C low-temperature impact is larger than or equal to 80 J, and the yield ratio is smaller than or equal to 0.80.

Description

Technical Field

[0001] The present invention belongs to the technical field of materials metallurgy, and particularly relates to a method for preparing low-cost Q355CRE hot-rolled H-beams. Background Art

[0002] In countries with large production and sales volumes of steel products, the status of H-beams has become increasingly important, and the production and sales volumes have also been increasing. To some extent, the level of H-beam production represents the level of a country's construction technology. Currently, in Western countries such as Europe and the United States, the production of H-beams accounts for 4% - 8% of the total steel production, while the production and sales volume of hot-rolled H-beams in Japan has reached 6% - 8% of the total production and sales volume of the country's steel products. In recent years, the production technology of H-beams has gradually matured, the output has been continuously increasing, and the product specifications have gradually developed towards serialization and diversification.

[0003] Currently, China has 35 section steel production lines, among which 24 production lines have the ability to produce hot-rolled H-beams, and the total annual production capacity reaches 22.35 million tons. Compared with developed countries, the proportion of hot-rolled H-beams in China's total steel consumption is relatively small, and there is still a large gap compared with developed countries, and there is still great room for growth. Therefore, in terms of the current development trend of H-beams, H-beams still have extremely huge market potential in China.

[0004] Patent No. 202010372949.X announced "A production process for low-cost Q355C steel plates", and its chemical composition is as follows: C: 0.11% - 0.20%, Si: ≤0.20 - 0.45%, Mn: 1.1% - 1.6%,

[0005] Alt: 0.015% - 0.045%, P: ≤0.025%, S: ≤0.015%, and the rest is Fe. The chemical composition is not much different from the standard range. In addition, the rolling process of the steel plate is quite different from that of H-beams and has no practical reference significance.

[0006] As the market in the construction industry gradually becomes saturated, the homogeneous competition of H-beams is becoming increasingly fierce. Controlling the manufacturing cost of H-beams has become the primary task of each steel mill. Due to the requirement of 0°C low-temperature impact toughness for Q355C hot-rolled H-beams, most steel mills need to add a certain amount of alloying elements to improve its strength and toughness when producing Q355C, which results in the problem of relatively high cost of Q355C hot-rolled H-beams. Summary of the Invention

[0007] The object of the present invention is to provide a method for preparing low-cost Q355CRE hot-rolled H-beams, and its performance indicators meet the following technical requirements: yield strength Rel≥355 MPa, tensile strength Rm≥490 MPa, elongation A≥23%, low-temperature impact at 0°C≥80 J, yield ratio≤0.80, CEV / %≤0.45.

[0008] To solve the above technical problems, the present invention adopts the following technical solutions:

[0009] A method for preparing low-cost Q355CRE hot-rolled H-beams of the present invention includes: steelmaking process flow: converter - secondary refining - continuous casting of special-shaped billets, rolling process flow: walking beam reheating furnace - high-pressure water descaling - BD rough rolling - CCS finish rolling - cooling - straightening, and is characterized in that: the technical parameters controlled in the rolling process are:

[0010] 1) Heating temperature is 1200 - 1240°C, and the total heating time≥2 hours;

[0011] 2) Starting rolling temperature≤1100°C;

[0012] 3) Final rolling temperature≤860°C;

[0013] The chemical composition mass percentage of the Q355CRE hot-rolled H-beam is: C: 0.17% - 0.21%, Si: 0.45% - 0.50%, Mn: 1.30% - 1.40%, P≤0.018%, S≤0.010%, Al:≥0.015%, RE: 0.0010% - 0.0020%, and the rest are Fe and other trace impurity elements.

[0014] Furthermore, the chemical composition mass percentage of the Q355CRE hot-rolled H-beam is: C: 0.19%, Si: 0.47%, Mn: 1.35%, P: 0.012%, S: 0.005%, Al: 0.015%, RE: 0.0016%, and the rest are Fe and other trace impurity elements.

[0015] Furthermore, the chemical composition mass percentage of the Q355CRE hot-rolled H-beam is: C: 0.19%, Si: 0.46%, Mn: 1.32%, P: 0.014%, S: 0.003%, Al: 0.016%, RE: 0.0013%, and the rest are Fe and other trace impurity elements.

[0016] Furthermore, the heating temperature is 1230°C, the total heating time is 2.8 h; the starting rolling temperature is 1080°C; the final rolling temperature is 840°C.

[0017] Furthermore, the heating temperature is 1228°C, the total heating time is 2.7 h; the starting rolling temperature is 1062°C; the final rolling temperature is 831°C.

[0018] Furthermore, the elongation of the prepared Q355CRE hot-rolled H-beam meets the requirement of ≥23%.

[0019] Furthermore, the impact value at 0°C of the prepared Q355CRE hot-rolled H-beam meets the requirement of ≥80 J.

[0020] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0021] 1) Adding a small amount of RE element can purify the steel quality and improve the low-temperature impact toughness of the steel. Since the RE element is a relatively inexpensive rare earth Ce alloy, the cost is lower.

[0022] 2) Adding a small amount of Al element to the steel can fix elements such as O and N in the steel and generate compounds to play a role in refining the grains.

[0023] 3) Since it is a special-shaped billet rolling H-beam, the heating time and final rolling temperature of the steel are minimized as much as possible, making the grains finer and improving the strength and toughness of the material.

[0024] Its performance indicators meet the following technical requirements: yield strength Rel≥355 MPa, tensile strength Rm≥490 MPa, elongation A≥23%, low-temperature impact at 0°C≥80 J, yield ratio≤0.80, CEV / %≤0.45. Specific embodiments

[0025] The present invention will be further described below through specific examples. The examples are only for the purpose of explanation, and the protection scope of the present invention is not limited to these examples.

[0026] The present invention will be further described below:

[0027] Table 1 shows the chemical composition weight percentage content, carbon equivalent and list of each embodiment of the present invention.

[0028] Table 2 shows the rolling steel process values of each example of the present invention.

[0029] Table 3 shows the list of test results such as mechanical properties of each embodiment of the present invention.

[0030] Table 1 shows the chemical composition and weight percentage content of each embodiment

[0031] Example C Si Mn P S Al RE CEV 1 0.19 0.47 1.35 0.012 0.005 0.015 0.0016 0.42 2 0.19 0.46 1.32 0.014 0.003 0.016 0.0013 0.42

[0032] Table 2 shows the rolling steel process values of each example of the present invention

[0033] Example Total heating time h Heating temperature °C Rolling start temperature °C Final rolling temperature °C 1 2.8 1230 1080 840 2 2.7 1228 1062 831

[0034] Table 3 shows the test results of mechanical properties and the like of each embodiment

[0035]

[0036] Through the analysis of the test data in Table 3: All mechanical property indexes meet the technical requirements and are even more excellent.

[0037] The embodiments described above are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A low-cost Q355CRE hot-rolled H-beam preparation method, comprising: Steelmaking process: converter - refining outside the furnace - continuous casting of special-shaped billets, steel rolling process: walking beam heating furnace - high-pressure water dephosphorization - BD initial rolling - CCS finishing rolling - cooling - straightening, characterized in that: the technical parameters controlled in the rolling process are: 1) Heating temperature 1200-1240℃, total heating time ≥ 2 hours; 2) Rolling temperature ≤ 1100℃; 3) Final rolling temperature ≤860℃; The chemical composition of the Q355CRE hot-rolled H-beam is as follows: C: 0.17% to 0.21%, Si: 0.45% to 0.50%, Mn: 1.30% to 1.40%, P≤0.018%, S≤0.010%, Al: ≥0.015%, RE: 0.0010% to 0.0020%, and the rest are Fe and other trace impurity elements.

2. The low-cost Q355CRE hot-rolled H-beam preparation method according to claim 1, characterized in that: The chemical composition of the Q355CRE hot-rolled H-beam is as follows: C: 0.19%, Si: 0.47%, Mn: 1.35%, P: 0.012%, S: 0.005%, Al: 0.015%, RE: 0.0016%, and the rest are Fe and other trace impurity elements.

3. The low-cost Q355CRE hot-rolled H-beam preparation method according to claim 1, characterized in that: The chemical composition of the Q355CRE hot-rolled H-beam is as follows: C: 0.19%, Si: 0.46%, Mn: 1.32%, P: 0.014%, S: 0.003%, Al: 0.016%, RE: 0.0013%, and the rest are Fe and other trace impurity elements.

4. The low-cost Q355CRE hot-rolled H-beam preparation method according to claim 2, characterized in that: Heating temperature is 1230℃, total heating time is 2.8h; starting rolling temperature is 1080℃; final rolling temperature is 840℃.

5. The low-cost Q355CRE hot-rolled H-beam preparation method according to claim 3, characterized in that: Heating temperature is 1228℃, total heating time is 2.7h; starting rolling temperature is 1062℃; final rolling temperature is 831℃.

6. The low-cost Q355CRE hot-rolled H-beam preparation method according to claim 4 or 5, characterized in that: The elongation of the prepared Q355CRE hot-rolled H-beam meets ≥23%.

7. The low-cost Q355CRE hot-rolled H-beam preparation method according to claim 1, characterized in that: The prepared Q355CRE hot-rolled H-beam has a 0°C impact value of ≥80J.

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