A production method for improving the strength of industrial pure iron for electrolytic aluminum

Abstract

The application discloses a production preparation method for improving the strength of industrial pure iron for electrolytic aluminum, and comprises the following steps: a steelmaking process; a steel rolling process; 1100 DEG C <= opening rolling temperature <= 1150 DEG C; 850 DEG C <= final rolling temperature <= 870 DEG C; the chemical composition mass percentage is as follows: C: <= 0.008%, Si: <= 0.03%, Mn: <= 0.06%, P <= 0.012%, S <= 0.007%, Al <= 0.050%, N >= 0.015%, RE >= 0.0050%; the rest is Fe and other trace impurity elements. The application aims to provide a production preparation method for improving the strength of industrial pure iron for electrolytic aluminum, and the strength index of the industrial pure iron can be effectively improved through reasonable chemical composition design and production process, so that Rel >= 200 MPa, Rm >= 290 MPa and A >= 25%.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of material metallurgy, and particularly relates to a production and preparation method for improving the strength of industrial pure iron for electrolytic aluminum. BACKGROUND

[0002] Pure iron can be used as electrode material of electrolyte and participate in the electrolysis process. In addition, pure iron can also play a catalytic role in the electrolysis process to promote the reaction. Furthermore, pure iron can also be used as structural material of electrolytic cell to provide stable support and conductive function.

[0003] The electrode flat steel is mainly used as the cathode of the electrolytic cell of the electrolytic aluminum enterprise to adjust the resistance of the furnace bottom of the electrolytic cell and the uniform distribution of the current, improve the horizontal current of the aluminum liquid, realize low-voltage production, and reduce the power consumption of the electrolytic aluminum direct current. Previously, the electrode flat steel was generally carbon structural steel (Q195, Q235, etc.). These common carbon steel materials are easy to obtain, and the electrode cost is low. However, the poor conductivity at high temperature, large resistance, and high power consumption of the common carbon steel materials restrict the further application of the common carbon steel material electrode. In general, the power consumption cost of the electrolytic aluminum enterprise accounts for more than 40% of the total cost. The strong demand of the electrolytic aluminum enterprise for reducing power consumption accelerates the continuous development and application of the high-conductive (SAE1006) and super-high-conductive (pure iron) electrode flat steel in the electrolytic aluminum enterprise.

[0004] As the structural material of the electrolytic cell, pure iron is required to have good electrical conductivity and mechanical strength. At the same time, pure iron also needs to withstand the pressure and corrosion of the gas and solution generated by the chemical reaction of the electrolytic cell to ensure the stability and long-term operation of the electrolytic cell. However, the strength of the industrial pure iron is lower than that of the common carbon steel, which affects the stability of the electrolytic cell. SUMMARY

[0005] The purpose of the present application is to provide a production and preparation method for improving the strength of industrial pure iron for electrolytic aluminum. Through reasonable chemical composition design and production process, the strength index of the industrial pure iron can be effectively improved, so that the R el of the industrial pure iron is greater than or equal to 200 MPa, the R m of the industrial pure iron is greater than or equal to 290 MPa, and the A of the industrial pure iron is greater than or equal to 25%.

[0006] To solve the above technical problems, the present application adopts the following technical scheme:

[0007] The present application is a production and preparation method for improving the strength of industrial pure iron for electrolytic aluminum, which comprises the following steps:

[0008] The steelmaking process is: desulfurized molten iron - converter - secondary refining - RH vacuum - continuous casting; wherein:

[0009] The converter smelting is double-slag operation, and the final slag basicity is controlled at 3.5;

[0010] LF ladle refining, argon blowing is carried out in the whole refining process;

[0011] RH deep vacuum time≥15min;

[0012] After the RH vacuum treatment is finished, 200 meters of iron-nitrogen wire is fed, and the soft blowing Ar time is 12min≤soft blowing Ar time≤16min after the wire feeding;

[0013] Continuous casting superheat≤30℃;

[0014] 0.55m / min≤casting speed≤0.62m / min;

[0015] Rolling process: slab heating-high pressure water phosphorus removal-Φ850 blooming mill-Φ700mm×3+Φ550mm×4 continuous rolling mill group rolling-water cooling-sawing-straightening-inspection-grinding-bundling-warehousing-shipping; wherein:

[0016] 1100℃≤rolling temperature≤1150℃;

[0017] 850℃≤finish rolling temperature≤870℃.

[0018] Further, the chemical composition in mass percent is: C:≤0.008%, Si:≤0.03%, Mn:≤0.06%, P≤0.012%, S≤0.007%, Al≤0.050%, N≥0.015%, RE≥0.0050%, the rest is Fe and other trace impurity elements.

[0019] Further, the chemical composition in mass percent is: C: 0.007%, Si: 0.025%, Mn: 0.055%, P: 0.011%, S: 0.005%, Al: 0.045%, N: 0.017%, RE: 0.0060%, the rest is Fe and other trace impurity elements.

[0020] Further, the chemical composition in mass percent is: C: 0.008%, Si: 0.020%, Mn: 0.046%, P: 0.010%, S: 0.005%, Al: 0.040%, N: 0.020%, RE: 0.0052%, the rest is Fe and other trace impurity elements.

[0021] Further, the mechanical properties meet: yield strength>228MPa, tensile strength>320MPa, elongation≥25%.

[0022] Some elements act as follows:

[0023] C: With the increase of carbon content, the hardenability and hardening of the steel increase, but the toughness and weldability of the steel decrease. Through the application of the present technology, the upper limit of carbon content is defined as ≤0.008% without affecting the electrical conductivity of industrial pure iron.

[0024] Mn: a solid solution strengthening element, which also shifts the C curve to the right, significantly improving the hardenability of the steel. Manganese improves the toughness and strength of the steel, but too much manganese can cause segregation. Through the present technology, the manganese content is ≤0.06%.

[0025] P, S: P and S are impurity elements in steel. P has a certain effect on improving corrosion resistance, but P is an element that is prone to segregation, which can cause severe segregation in local parts of the steel, reducing plasticity and toughness, and is extremely harmful to low temperature toughness. S is prone to segregation and enrichment in steel, which is harmful to corrosion resistance. In the present steel, the sulfur and phosphorus content levels are strictly controlled in terms of metallurgical quality, i.e. P: ≤0.012%; S: ≤0.007%.

[0026] Si: Si can improve the corrosion resistance of steel and is often added to stainless steel, low alloy steel and corrosion resistant alloy to improve the corrosion resistance of these alloys, making them resistant to chloride stress corrosion cracking, pitting corrosion, hot concentrated nitric acid corrosion, oxidation and seawater corrosion. In the present invention, Si is used as a deoxidizer for industrial pure iron, and the percentage content of Si is ≤0.03%.

[0027] Al: Al has a strong affinity with O and N and is a deoxidizing and nitrogen-fixing agent during steelmaking. Aluminum can effectively reduce the austenite phase region in steel, refine the intrinsic grain size of steel, reduce the notch sensitivity of steel, reduce and eliminate the aging phenomenon of steel, especially reduce the ductile-brittle transition temperature of steel and improve the low temperature toughness of steel. However, when the solid solution Al content in steel exceeds a certain value, the austenite grains tend to grow and coarsen. The Al content in the present steel is designed to be ≤0.050%.

[0028] N: In steel, V and C form V(C, N) compounds, which have the effect of refining grains and strengthening the ferrite matrix. Al reacts with N to form AlN particles, which have a pinning effect on dislocations, thereby improving the strength and toughness of the material. Therefore, the N content in the present invention is designed to be ≥0.015%.

[0029] RE: RE has the effects of purification and significant modification in steel. The cleanliness of steel is continuously improved, and the micro-alloying effect of rare earth elements is increasingly prominent. Rare earth micro-alloying includes the solid solution strengthening of trace rare earth elements, the interaction of rare earth elements with other solute elements and compounds, the existence state (atoms, inclusions or compounds) of rare earth elements, size, morphology and distribution, especially the segregation at grain boundaries, and the influence of rare earth on the surface and matrix structure of steel. Therefore, the RE content in the present invention is designed to be ≥0.0050%.

[0030] Compared with the prior art, the present application has the beneficial technical effects:

[0031] 1) The AlN particles generated by the reaction of Al and N have pinning effect on dislocations, thereby improving the strength and toughness of the material.

[0032] 2) The strength of the industrial pure iron is improved by the solid solution strengthening of rare earth elements, the interaction of rare earth elements with other solute elements and compounds, and the denaturation of inclusions at the grain boundary of the industrial pure iron.

[0033] 3) The grain size of the industrial pure iron is refined by using a low final rolling temperature, and the grain size of the industrial pure iron is refined by increasing the undercooling of the industrial pure iron after water cooling after rolling. DETAILED DESCRIPTION

[0034] The present application will be further described below through specific examples, and the examples are only for the purpose of explanation, and the protection scope of the present application is not limited to the examples.

[0035] The present application will be further described below:

[0036] Table 1 is a list of chemical composition and weight percentage content of each embodiment of the present application.

[0037] Table 2 is a list of steelmaking process control parameters of each embodiment of the present application.

[0038] Table 3 is a list of rolling process control parameters of each embodiment of the present application.

[0039] Table 4 is a list of mechanical property test results of each embodiment of the present application.

[0040] Table 1 Chemical composition and weight percentage content of the example

[0041] Embodiments C Si Mn P S N Al RE 1 0.007 0.025 0.055 0.011 0.005 0.017 0.045 0.0060 2 0.008 0.020 0.046 0.010 0.005 0.020 0.040 0.0052

[0042] Table 2 Steelmaking process control parameters of each embodiment of the present application

[0043]

[0044] Table 3 Rolling process control parameters of each embodiment of the present application

[0045]

[0046] Table 4 List of mechanical property test results of each embodiment of the present application

[0047]

[0048]

[0049] The above test data can show that:

[0050] The process parameters and component ranges of the present application can realize the method.

[0051] The yield strength, tensile strength and elongation of the steel product of the embodiment of the present application all meet the performance requirements.

[0052] The above-described embodiments are only preferred modes of the present application and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope defined by the claims of the present application.

Claims

1. A method of improving the strength of commercial purity iron for use in the production of electrolytic aluminium, characterised in that, Comprise: Steel-making process: desulphurized hot metal-converter- secondary refining-RH vacuum-continuous casting; wherein: Complex blowing converter smelting, using double slag operation, the final slag basicity is controlled at 3.5; LF ladle refining, argon blowing operation is carried out throughout the refining process; RH deep vacuum time≥15min; After the end of RH vacuum treatment, 200 meters of iron-nitrogen wire is fed, and the soft blowing Ar time is 12min≤≤16min after wire feeding; Continuous casting superheat≤30℃; 0.55m / min≤casting speed≤0.62m / min; Rolling process: billet heating-high pressure water desulphurization-Φ850 cogging mill-Φ700mm×3+Φ550mm×4 rolling mill rolling-water cooling-sawing-straightening-inspection-grinding-bundling-warehousing-shipping; wherein: 1100℃≤rolling temperature≤1150℃; 850℃≤final rolling temperature≤870℃; The chemical composition is as follows: C:≤0.008%, Si:≤0.03%, Mn:≤0.06%, P≤0.012%, S≤0.007%, Al≤0.050%, N≥0.015%, RE≥0.0050%, the rest is Fe and other trace impurity elements.

2. The production preparation method of improving the strength of industrial pure iron for electrolytic aluminum according to claim 1, characterized in that, The chemical composition is as follows: C: 0.007%, Si: 0.025%, Mn: 0.055%, P: 0.011%, S: 0.005%, Al: 0.045%, N: 0.017%, RE: 0.0060%, the rest is Fe and other trace impurity elements. The chemical composition is as follows: C: 0.008%, Si: 0.020%, Mn: 0.046%, P: 0.010%, S: 0.005%, Al: 0.040%, N: 0.020%, RE: 0.0052%, the rest is Fe and other trace impurity elements.

3. The production preparation method of improving the strength of industrial pure iron for electrolytic aluminum according to claim 1, characterized in that, ​ 4. The production preparation method of improving the strength of industrial pure iron for electrolytic aluminum according to claim 1, characterized in that, The mechanical properties meet: R el ≥ 200 MPa, R m ≥ 290 MPa, A ≥ 25%.

Images