High-boron high-chromium alloy cast iron fire grate bar of sintering machine trolley furnace and manufacturing method of high-boron high-chromium alloy cast iron fire grate bar

Abstract

The invention discloses a high-boron high-chromium alloy cast iron fire grate bar of a sintering machine trolley furnace and a manufacturing method of the high-boron high-chromium alloy cast iron fire grate bar, and belongs to the technical field of smelting equipment, and the high-boron high-chromium alloy cast iron fire grate bar comprises the following material components in percentage by mass: 0.1-5% of B, 1.0-2.0% of C, 0.5-1.5% of Si, 0.5-1.5% of Mn, 15.0-22.0% of Cr, 0.1-2% of Ni, 0.1-2% of Mo, 0.01-0.06% of P, 0.01-0.06% of S and the balance of Fe. Comprising the following steps: modeling a casting casting model, preparing furnace charge according to the percentage, performing conventional deoxidization and nitrogen fixation treatment on a melt during smelting, controlling the smelting temperature to be 1500-1600 DEG C, immediately pouring after smelting to the temperature, controlling the pouring temperature to be 1450-1550 DEG C, and performing sand removal and cleaning on the cast fire grate casting, thereby obtaining the fire grate casting which can be used without heat treatment. The material can resist high-temperature oxidation, the strength and toughness in a high-temperature environment are improved, the service life is greatly prolonged, and the operation efficiency of equipment is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of smelting equipment, in particular to a high-boron and high-chromium alloy cast iron grate bar for a sintering machine bogie furnace, and also to a method for manufacturing the high-boron and high-chromium alloy cast iron grate bar for the sintering machine bogie furnace. Background Art

[0002] Grate bars are a crucial component of the trolley furnaces used in steel production. The upper portion of the grate bar carries the charge, while the ends support the sintering trolley. The lower curved legs of the grate bar, hooked onto the trolley, secure the bar against falling during the trolley's rollover and unloading. Furthermore, they provide support and reinforcement when the top of the grate bar is under pressure from the charge, preventing it from bending or breaking.

[0003] The working environment of grate bars is harsh. First, the temperature is high and varies greatly: the temperature of sintered ore can reach 1100℃, while the temperature of grate bars is generally 800-1000℃. After unloading, the temperature of grate bars drops rapidly to 100-300℃; secondly, the grate bars bear the heavy pressure of sintered ore during high-temperature sintering; thirdly, the grate bars are also subject to the erosion of high-temperature and high-speed powder-gas two-phase flow and the corrosion of CO, CO2, NOx, SO2 and water vapor in high-temperature flue gas; fourthly, the grate bars are also subject to the impact and abrasive wear of sintered ore during loading and unloading.

[0004] The most widely used grate bar material is high-chromium alloy cast iron. This material contains high levels of chromium (chemical composition percentage = 25-28% by mass), carbon (chemical composition percentage = 1.5-2.5% by mass), and other minor elements to enhance its strength and toughness in high-temperature environments. However, the high Cr and C content easily forms a large amount of Cr7C3 network chromium-carbon compounds during the casting process. These chromium-carbon compounds are distributed at the grain boundaries, reducing the effective Cr content in the matrix, affecting the material's resistance to intergranular corrosion and significantly reducing its high-temperature oxidation resistance. Furthermore, the high hardness and brittleness of the martensitic structure and Cr7C3 chromium-carbon compounds in the matrix reduce the material's high-temperature toughness. Furthermore, the high chromium content significantly increases material cost. The service life of high-chromium alloy cast iron grate bars is only approximately 18 months. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a high-boron and high-chromium alloy cast iron grate bar for a sintering machine trolley furnace that is resistant to high-temperature oxidation, improves strength and toughness in high-temperature environments, significantly extends service life, and improves equipment operation efficiency.

[0006] Another object of the present invention is to provide a method for manufacturing the high-boron and high-chromium alloy cast iron grate bars of the sintering machine trolley furnace.

[0007] The present invention provides a high-boron alloy cast iron grate bar for a sintering machine trolley furnace, wherein the material composition by weight percentage is as follows: B=0.1-5%, C=1.0-2.0%, Si=0.5-1.5%, Mn=0.5-1.5%, Cr=15.0-22.0%, Ni=0.1-2%, Mo=0.1-2%, P=0.01-0.06%, S=0.01-0.06%, and the balance is Fe.

[0008] The high boron alloy cast iron grate bars of the above-mentioned sintering machine trolley furnace preferably have the following material composition by mass percentage (wt%): B=1.5%, C=1.2%, Si=0.6%, Mn=1.1%, Cr=20%, Ni=0.3%, Mo=0.3%, P=0.03%, S=0.03%, and the balance is Fe.

[0009] The present invention provides a method for manufacturing a high-boron and high-chromium alloy cast iron grate bar material for a sintering machine trolley furnace, comprising the following steps: (1) The casting model is made by sand mold technology; (2) The furnace charge is prepared according to the percentage of high boron alloy cast iron grate bars of the above-mentioned sintering machine trolley furnace; (3) Using a medium frequency induction furnace with alkaline lining for smelting, the charge is added in the normal order; (4) During smelting, the melt is subjected to conventional deoxidation and nitrogen fixation treatment, and the smelting temperature is controlled at 1500-1600°C; (5) Pour the smelted steel immediately after it reaches the desired temperature, and control the pouring temperature between 1450 and 1550°C. (6) After the cast grate bar castings are cleaned and sanded, they can be used without heat treatment.

[0010] Compared with existing technologies, the present invention offers significant advantages. The above technical solutions demonstrate that the present invention utilizes multi-component alloying to ensure the abundance of high-temperature oxidation- and corrosion-resistant phases in the alloy structure, raising the material's liquidus temperature and preventing localized overheating and overburning of the grate bars during sintering. Furthermore, the grate bar castings of the present invention can be used directly without heat treatment, further reducing production costs. Their actual service life is 2-3 times that of high-chromium alloy cast iron grate bars. DETAILED DESCRIPTION

[0011] The following will be combined with preferred embodiments to describe in detail the specific implementation, structure, features and effects of a high-boron and high-chromium alloy cast iron grate bar for a sintering machine trolley furnace and a manufacturing method thereof proposed by the present invention. Example 1: A method for manufacturing a high-boron and high-chromium alloy cast iron grate bar material for a sintering machine trolley furnace comprises the following steps: (1) Using green sand process to make casting patterns; (2) Casting materials are prepared according to the following composition ratios: (mass percentage wt%) C=1.2%, Si=0.6%, Mn=1.1%, Cr=20%, Ni=0.3%, Mo=0.3%, B=3.0%, P=0.03%, S=0.03%, and the balance is Fe.

[0012] (3) Using a medium frequency induction furnace with alkaline lining for smelting, the charge is added in the normal order; (4) The melting temperature of the casting material is controlled at 1500℃, and the melt is deoxidized and nitrogen fixed during melting; (5) Pour the smelted steel immediately after it reaches the desired temperature, and control the pouring temperature at 1450°C. (6) After the cast grate bar castings are cleaned and sanded, they can be used without heat treatment.

[0013] Example 2: A method for manufacturing a high-boron and high-chromium alloy cast iron grate bar material for a sintering machine trolley furnace comprises the following steps: (1) Using carbon dioxide hardened water glass sand process to make casting models; (2) Casting materials are prepared according to the following composition ratios: (mass percentage wt%) C=1.1%, Si=0.8%, Mn=1.2%, Cr=21%, Ni=0.4%, Mo=0.4%, B=1.5%, P=0.04%, S=0.04%, and the balance is Fe.

[0014] (3) Using a medium frequency induction furnace with alkaline lining for smelting, the charge is added in the normal order; (4) The melting temperature of the casting material is controlled at 1550°C. During melting, the melt is deoxidized and nitrogen fixed; (5) Pour immediately after melting to temperature, and control the pouring temperature at 1500℃; (6) After the cast grate bar castings are cleaned and sanded, they can be used without heat treatment.

[0015] Example 3: A method for manufacturing a high-boron and high-chromium alloy cast iron grate bar material for a sintering machine trolley furnace comprises the following steps: (1) Using coated sand process to make casting models; (2) Casting materials are prepared according to the following composition ratios: (mass percentage wt%) C=1.2%, Si=0.7%, Mn=1.2%, Cr=22%, Ni=0.3%, Mo=0.4%, B=2.5%, P=0.05%, S=0.05%, and the balance is Fe.

[0016] (3) Using a medium frequency induction furnace with alkaline lining for smelting, the charge is added in the normal order; (4) The melting temperature of the casting material is controlled at 1520℃, and the melt is deoxidized and nitrogen fixed during melting; (5) Pour immediately after melting to temperature, and control the pouring temperature at 1480℃; (6) After the cast grate bar castings are cleaned and sanded, they can be used without heat treatment.

[0017] Test example: The high-boron high-chromium alloy cast iron grate bars prepared in Examples 1-3 were oxidized at 900°C for 500 hours. The test results were as follows: Conclusion: The above test data show that the high temperature oxidation resistance of high boron high chromium alloy cast iron furnace grate material is about 3 times that of high chromium alloy cast iron furnace grate material.

[0018] The above method is only a preferred embodiment of the present invention and does not impose any formal limitation on the present invention. Without departing from any technical solution content of the present invention, any simple modification, equivalent change and modification made to the above implementation case based on the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A high-boron alloy cast iron grate bar for a sintering machine bogie furnace, wherein the material composition by mass percentage is as follows: B=0.1~5%, C=1.0~2.0%, Si=0.5~1.5%, Mn=0.5~1.5%, Cr=15.0~22.0%, Ni=0.1~2%, Mo=0.1~2%, P=0.01~0.06%, S=0.01~0.06%, and the balance is Fe.

2. The high boron alloy cast iron grate bar of a sintering machine trolley furnace according to claim 1, wherein the material composition by mass percentage is as follows: B=1.5%, C=1.2%, Si=0.6%, Mn=1.1%, Cr=20%, Ni=0.3%, Mo=0.3%, P=0.03%, S=0.03%, and the balance is Fe.

3. A method for manufacturing a high-boron and high-chromium alloy cast iron grate bar material for a sintering machine trolley furnace, comprising the following steps: (1) The casting model is made by sand mold technology; (2) The furnace charge is prepared according to the percentage of high boron alloy cast iron grate bars of the above-mentioned sintering machine trolley furnace; (3) Using a medium frequency induction furnace with alkaline lining for smelting, the charge is added in the normal order; (4) During smelting, the melt is subjected to conventional deoxidation and nitrogen fixation treatment, and the smelting temperature is controlled at 1500-1600°C; (5) Pour the smelted steel immediately after it reaches the desired temperature, and control the pouring temperature between 1450 and 1550°C. (6) After the cast grate bar castings are cleaned and sanded, they can be used without heat treatment.

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