Forklift portal frame steel with high strength, corrosion resistance and contact fatigue resistance and preparation process of forklift portal frame steel

Abstract

The invention relates to the technical field of metallurgy, in particular to high-strength, corrosion-resistant and contact-fatigue-resistant forklift portal steel and a preparation process thereof.The forklift portal steel comprises the chemical components of C, Si, Mn, P, S, Cr, Ni, Mo, Cu, Alt, Nb, V, N and the balance Fe and a small amount of inevitable impurities, and the specific steps are as follows: a smelting process; the smelting process comprises electric furnace smelting, LF refining, VD treatment, continuous casting and casting blank slow cooling processes, and the rolling process comprises heating, temperature-controlled rolling, temperature-controlled cooling, straightening and subsequent procedures. Compared with common low-alloy steel, the prepared forklift portal steel has better atmospheric corrosion resistance in the use and operation process, and the requirements of high-strength and high-precision forklift portal steel are met.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to a high-strength, corrosion-resistant, and contact fatigue-resistant forklift mast steel and its preparation process. Background Technology

[0002] The mast is a crucial component of a forklift's lifting system. With the rapid development of the global forklift manufacturing and warehousing logistics industries, the demand for lifting height in forklifts and reach trucks is increasing year by year. Due to the limitations of mast steel strength and precision, the highest lifting height for domestic forklifts and reach trucks is currently 15 meters, and high-end mast steel materials are still largely imported. As forklift lifting increases, users are also placing new demands on the performance of mast steel. On the one hand, due to the requirements of lifting height and cargo weight, mast steel must have a high yield strength of over 420MPa. On the other hand, currently, domestic mast steel is prone to peeling and flaking after 20,000 cycles, seriously affecting the stability and safety of forklift operation. In addition, forklifts operate in harsh environments, and the mast may require corrosion resistance. Therefore, there is an urgent need for high-strength, corrosion-resistant, and contact fatigue-resistant forklift mast steel. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a high-strength, corrosion-resistant and contact fatigue-resistant forklift mast steel and its preparation process to address the pain point that the strength and contact fatigue of the mast steel currently on the market do not meet the requirements of high-precision, high-mast forklifts.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a high-strength, corrosion-resistant, and contact fatigue-resistant forklift mast steel, wherein the chemical components of the forklift mast steel, by weight percentage, are: C: 0.10-0.25%, Si: 0.10-0.50%, Mn: 1.30-1.65%, P: ≤0.020%, S≤0.015%, Cr: ≤0.30%, Ni: 0.05-0.50%, Mo: 0.01-0.50%, Cu: 0.10-0.50%, Alt: 0.010-0.050%, Nb: 0.010-0.060%, V: 0.01-0.10%, N: 0.0050-0.0100%, with the balance being Fe and a small amount of unavoidable impurities.

[0005] A preparation process for a high-strength, corrosion-resistant, and contact fatigue-resistant forklift mast steel, the specific steps of which are as follows: Step 1, Smelting process; Step two, rolling process.

[0006] As a further aspect of the present invention, the smelting process includes electric furnace smelting, LF refining, VD treatment, continuous casting, and slow cooling of the billet.

[0007] As a further aspect of the present invention, the specific process of the electric furnace smelting process is as follows: molten iron, scrap steel, and some alloy raw materials are added to an electric furnace for smelting to obtain molten steel, and then subjected to dephosphorization treatment to control P: ≤0.020%; The specific process of the LF refining process is as follows: the molten steel smelted in the electric furnace is transferred to the LF furnace for refining and desulfurization treatment, the S content is controlled to be ≤0.015%, and the alloy element content is adjusted to the required range. The specific process of the VD treatment is as follows: the refined molten steel is subjected to VD vacuum treatment, the vacuum holding time is ≥15min, the H content in the molten steel is reduced and controlled to H: ≤0.0002%, and the molten steel is homogenized at the same time. The specific process of the continuous casting process is as follows: molten steel is transferred to a tundish, and then the molten steel in the tundish is poured into a crystallizer. Under the action of a straightening machine, the solidified billet shell leaves the crystallizer. The continuous casting process uses electromagnetic stirring and light pressure to prepare 150*220 square billets, and the straightening machine speed is 1.3-1.8 m / min. The specific process of the billet slow cooling process is as follows: in order to prevent the billet from cracking, the continuous casting is placed in a slow cooling pit to cool to room temperature.

[0008] As a further aspect of the present invention, the rolling process includes heating, temperature-controlled rolling, temperature-controlled cooling, straightening, and subsequent processes.

[0009] As a further aspect of the present invention, the specific process of the heating process is as follows: the heating temperature of the billet is 1180-1250℃, the soaking time is ≥15min, and the total furnace time is 170-190min. The specific process of the temperature-controlled rolling process is as follows: after the billet is taken out of the furnace, it is rolled, and the final rolling temperature is 780-910℃. The specific process of the temperature-controlled cooling process is as follows: natural cooling to 440-460℃ followed by rapid water cooling to room temperature.

[0010] Because this invention adopts the above technical solution, its advantages and positive effects are as follows: 1. This invention, through specific component design and online controlled rolling and cooling, enables the product to achieve a strength of 440MPa, meeting the requirements for high-strength, high-precision forklift mast steel, with a lifting height of ≥15 meters.

[0011] 2. The forklift mast steel prepared by this invention can meet the requirements of no peeling or flaking after 20,000 fatigue tests and slight wear of ≤0.2mm after 80,000 fatigue tests, demonstrating excellent fatigue resistance.

[0012] 3. The forklift mast steel prepared by this invention has better atmospheric corrosion resistance than ordinary low alloy steel during use and operation. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the metallographic features of an embodiment of the forklift mast steel of the present invention. Detailed Implementation

[0014] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0015] like Figure 1 As shown, Figure 1 This is a metallographic schematic diagram of the forklift mast steel of the present invention. The microstructure consists of ferrite, pearlite and bainite, with fine and uniform grains.

[0016] Specifically, the forklift mast steel of the present invention comprises the following chemical components by weight percentage: C: 0.10-0.25%, Si: 0.10-0.50%, Mn: 1.30-1.65%, P: ≤0.020%, S≤0.015%, Cr: ≤0.30%, Ni: 0.05-0.50%, Mo: 0.01-0.50%, Cu: 0.10-0.50%, Alt: 0.010-0.050%, Nb: 0.010-0.060%, V: 0.01-0.10%, N: 0.0050-0.0100%, with the balance being Fe and a small amount of unavoidable impurities.

[0017] Furthermore, a method for producing forklift mast steel includes the following preparation steps: (1): Smelting process; I. The chemical composition of each embodiment of the present invention is shown in Table 1, after processes such as smelting, LF refining, and vacuum treatment; Table 1. Chemical composition (wt%) of various embodiments of the present invention 2. Molten steel is poured into the crystallizer through the tundish, and the solidified billet shell leaves the crystallizer through the action of the straightening machine; During the continuous casting process, electromagnetic stirring is activated and light pressure is applied. The casting speed in Examples 1-4 is 1.35-1.78 m / min. After the billet is cut to length, it is placed in a slow cooling pit for slow cooling.

[0018] (2): Rolling process: including heating, rolling, online cooling, online straightening and subsequent processes; I. The heating processes of various embodiments of the present invention are shown in Table 2; Table 2 Heating processes of various embodiments of the present invention II. The rolling and cooling processes of each embodiment of the present invention are shown in Table 3.

[0019] Table 3 Rolling processes of various embodiments of the present invention (3): Mechanical properties I. The mechanical properties of each embodiment of the present invention are shown in Table 4.

[0020] Table 4 Mechanical properties of various embodiments of the present invention As shown in Tables 1-4, this invention, through specific composition design and online controlled rolling and cooling, achieves a product strength of 440MPa, meeting the requirements for high-strength, high-precision forklift mast steel. During operation, it exhibits superior atmospheric corrosion resistance compared to ordinary low-alloy steel. The lifting height can reach ≥15 meters. The forklift mast steel prepared by this invention can withstand 20,000 fatigue cycles without peeling or flaking, and after 80,000 fatigue cycles, the wear is minimal (≤0.2mm), demonstrating excellent fatigue resistance. This invention provides superior forklift mast steel.

[0021] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and various changes or modifications can be made to these embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is defined only by the appended claims.

Claims

1. A high-strength, corrosion-resistant, and contact fatigue-resistant forklift mast steel, characterized by: The chemical composition of the forklift mast steel, by weight percentage, is as follows: C: 0.10-0.25%, Si: 0.10-0.50%, Mn: 1.30-1.65%, P: ≤0.020%, S≤0.015%, Cr: ≤0.30%, Ni: 0.05-0.50%, Mo: 0.01-0.50%, Cu: 0.10-0.50%, Alt: 0.010-0.050%, Nb: 0.010-0.060%, V: 0.01-0.10%, N: 0.0050-0.0100%, with the balance being Fe and a small amount of unavoidable impurities.

2. The preparation process of a high-strength, corrosion-resistant, and contact fatigue-resistant forklift mast steel according to claim 1, characterized in that: Specific steps as follows: Step 1, Smelting process; Step two, rolling process.

3. The preparation process of a high-strength, corrosion-resistant, and contact fatigue-resistant forklift mast steel according to claim 2, characterized in that: The smelting process includes electric furnace smelting, LF refining, VD treatment, continuous casting, and slow cooling of the billet.

4. The preparation process of a high-strength, corrosion-resistant, and contact fatigue-resistant forklift mast steel according to claim 3, characterized in that: The specific process of the electric furnace smelting process is as follows: molten iron, scrap steel, and some alloy raw materials are added to the electric furnace for smelting to obtain molten steel, and then subjected to dephosphorization treatment to control P: ≤0.020%; The specific process of the LF refining process is as follows: the molten steel smelted in the electric furnace is transferred to the LF furnace for refining and desulfurization treatment, the S content is controlled to be ≤0.015%, and the alloy element content is adjusted to the required range. The specific process of the VD treatment is as follows: the refined molten steel is subjected to VD vacuum treatment, the vacuum holding time is ≥15min, the H content in the molten steel is reduced and controlled to H: ≤0.0002%, and the molten steel is homogenized at the same time. The specific process of the continuous casting process is as follows: molten steel is transferred to a tundish, and then the molten steel in the tundish is poured into a crystallizer. Under the action of a straightening machine, the solidified billet shell leaves the crystallizer.

5. Electromagnetic stirring and light pressure are used in the continuous casting process to prepare 150*220 square billets. The drawing speed of the straightening machine is 1.3-1.8m / min. The specific process of the slow cooling process for the billet is as follows: to prevent the billet from cracking, the continuous casting is placed in a slow cooling pit to cool to room temperature. The preparation process of a high-strength, corrosion-resistant, and contact fatigue-resistant forklift mast steel according to claim 2 is characterized in that: The rolling process includes heating, temperature-controlled rolling, temperature-controlled cooling, straightening, and subsequent processes.

6. The high-strength, corrosion-resistant, and contact fatigue-resistant forklift mast steel and its preparation process according to claim 5, characterized in that: The specific process of the heating process is as follows: the heating temperature of the billet is 1180-1250℃, the soaking time is ≥15min, and the total time in the furnace is 170-190min; The specific process of the temperature-controlled rolling process is as follows: after the billet is taken out of the furnace, it is rolled, and the final rolling temperature is 780-910℃. The specific process of the temperature-controlled cooling process is as follows: natural cooling to 440-460℃ followed by rapid water cooling to room temperature.

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