Alloy pad for large scale walking beam furnace and method for manufacturing the same

Abstract

The application discloses an alloy cushion block for a large walking beam heating furnace and a preparation method thereof, and the preparation method comprises the following steps: S1, determining the melting point of the alloy cushion block based on the atomic penetration depth of an alloy B containing FeO on multiple different alloy A with a melting point higher than that of the alloy B; S2, studying the load-bearing condition of the alloy cushion block to determine the required compressive strength; S3, designing the composition of the alloy cushion block; and S4, carrying out the industrial design of the alloy cushion block and starting smelting. Through reasonable alloy composition and production process design, the application provides a high-temperature heat-resistant alloy cushion block, improves the strength and melting point of the alloy cushion block, enables the alloy cushion block to maintain high strength at high temperature, solves the problem of FeO bonding in a molten state, reduces the phenomenon of heating furnace nodulation, and has universality and is suitable for various casting processes.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy, specifically to an alloy pad block for a large walking beam furnace and its preparation method. Background Technology

[0002] Some billet heating furnaces in steel rolling mills have long service lives, severely aged equipment, and low levels of automation, making it impossible to automatically heat steel. Billet heating is done manually. In addition, unstable gas pressure and calorific value cause uneven heating of billets, resulting in iron oxide scale on the lower surface of the billets and even molten steel adhering to the walking beam pads of the heating furnace, forming nodules. This prevents the hot rolling heating furnace from pouring steel normally and smoothly. Subsequently, the billets are severely deviated on the walking beam, causing steel drop accidents and furnace shutdowns.

[0003] Another problem with nodules is that they penetrate the bottom of the steel billet, forming holes. During subsequent hot working, the effects of these holes are directly transferred to the final product, such as streaks caused by the holes. These tiny streaks are a fatal hazard for high-end products. For example, if streaks appear on heavy rail products, they may cause the rails to break under the high-frequency vibration of the train's flywheel, leading to a major accident. Nodules on the walking beams of the heating furnace cannot be eliminated automatically. In the past, they could only be eliminated by opening the furnace door during equipment maintenance and striking them with iron pipes, which was labor-intensive for workers and posed safety hazards. Sometimes, the nodules were too tightly adhered or too large to be effectively eliminated.

[0004] Investigation revealed that the formation of lumps in the heating furnace was caused by the prolonged presence of detached iron oxide scale in a weakly reducing atmosphere. Some of the iron oxide scale was reduced to FeO by reducing gases such as CO. FeO has a melting point of only 1369℃ and a softening temperature of 1280℃. 1280℃ is the normal heating temperature for many steel grades in the heating furnace. Therefore, under heavy pressure, the molten FeO is prone to sticking to the load-bearing pads, resulting in accumulation and the formation of lumps.

[0005] Further laboratory research revealed that surface atomic penetration occurred between the formed nodules and the supporting pads they adhered to, resulting in a strong bond that prevented them from being lifted or falling off during the movement of the billet in the heating furnace. Traditional methods for eliminating and inhibiting nodule formation involve using weak oxidation (1.5-3%) or strong oxidation (5-10%) combined with rapid heating in the heating furnace to prevent the formation of FeO during billet heating. However, this approach results in large-area oxidation loss, with a loss rate 0.1-0.3% higher than normal and a unit consumption 0.1-0.4 GJ / t higher than normal, making it counterproductive. It also significantly complicates production organization. Furthermore, some heating furnaces cannot precisely control the O2 content, making nodule elimination impossible.

[0006] Therefore, providing a high-temperature heat-resistant alloy pad for a heating furnace that maintains high strength at high temperatures and completely solves the problem of FeO adhesion in the molten state has become a technical problem that urgently needs to be solved by those skilled in the art.

[0007] Therefore, existing technologies still need improvement. Summary of the Invention

[0008] The main objective of this invention is to provide an alloy pad for a large walking beam furnace and its preparation method, so as to solve the technical problems in the prior art where FeO bonding in the molten state and nodule formation of high-temperature alloy pads for furnaces affect the safe production of the furnace and the quality of the final product.

[0009] According to some embodiments of the present invention, a method for preparing alloy pads for large walking beam furnaces is proposed, which includes the following steps:

[0010] S1. The melting point of the alloy pad is determined based on the atomic penetration depth of FeO-containing alloy B on alloy A with multiple different melting points, wherein the melting point of alloy A is higher than that of alloy B.

[0011] S2. Conduct a load-bearing study on the alloy pads to determine the required compressive strength;

[0012] S3. Design the composition of the alloy pad;

[0013] S4. Conduct smelting industrial design for the alloy pad and begin smelting.

[0014] In an embodiment of the present invention, step S1 includes:

[0015] S11. Heat the alloy A and the alloy B to the melting point temperature of the alloy B respectively;

[0016] S12. Pour molten alloy B onto the surface of alloy A and cool to room temperature;

[0017] S13. Measure the atomic penetration depth on alloy A after cooling;

[0018] S14. Determine the melting point of the alloy pad based on the melting point of alloy A with an atomic penetration depth of 0 mm.

[0019] In an embodiment of the present invention, the FeO content in alloy B is ≥90% by weight percentage.

[0020] In an embodiment of the present invention, steps S2 and S3 include: determining the required compressive strength and designing the composition of the alloy pad based on the current process requirements of the heating furnace.

[0021] In an embodiment of the present invention, for steel billets in a heating furnace with a load-bearing requirement of 8-12 MPa, the compressive strength of the alloy pad is ≥33 MPa.

[0022] In an embodiment of the present invention, for a heating furnace with a heating range of 0-1350°C, a V and Ti micro-alloying process is used for composition design. The alloy pad has the following weight percentage composition: V 2-12%, Ti 1-3%, Co 20-50%, Cr 50-60%, Ni 10-30%, Mo 5-8%, Al 2-5%, with the remainder being Fe and unavoidable impurities.

[0023] In embodiments of the present invention, the Co content is controlled with a deviation of ±5% according to the grade of different alloy pads, and the Co, Cr, Ni and Al are all industrially pure and have a content of 99.99% or higher.

[0024] In an embodiment of the present invention, the smelting is carried out in a vacuum electric furnace with a vacuum degree of 5-7 MPa, and the final smelting temperature is 100-300°C higher than the highest melting point temperature of the added alloy.

[0025] In an embodiment of the present invention, under the premise of smelting the base material, the alloying elements are added in the order of Ni, Cr, and Co.

[0026] Furthermore, embodiments of the present invention also disclose an alloy pad for a large walking beam furnace, which is manufactured using any of the preparation methods described above.

[0027] By adopting the above technical solution, the present invention has at least the following beneficial effects:

[0028] This invention provides an alloy pad for a large walking beam furnace and its preparation method. Through comprehensive research on thermal engineering, welding, and materials science, the strength and melting point of the pad are improved, enabling it to maintain high strength at high temperatures and solving the problem of FeO adhesion in the molten state. By studying the adhesion principle, it is determined that the high temperature generated by electrical discharge melts the metal to form a molten pool, and the molten metals interpenetrate to complete the fusion welding. If a high-melting-point, high-strength alloy pad is used, the iron oxide scale will not adhere to the pad surface and form nodules. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 A process flow diagram of a method for preparing alloy pads for a large walking beam furnace, as disclosed in some embodiments of the present invention, is shown. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0032] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0033] Traditional methods largely tolerate the dead zone of regulating valves, severely limiting control accuracy and causing furnace oscillations. This invention proposes a technique to solve the problem of furnace temperature oscillations caused by the dead zone of the regulating valve in the intelligent temperature model setting of steel rolling furnaces. Based on existing models and considering the characteristics of the dead zone, this technique adjusts and alarms for dead zones below 100°C, and simultaneously stops the intelligent temperature model from controlling the furnace temperature for dead zones above 100°C, pending further processing.

[0034] Some embodiments of the present invention disclose a method for preparing alloy pads for large walking beam furnaces, which includes the following steps:

[0035] S1. The melting point of the alloy pad is determined based on the atomic penetration depth of FeO-containing alloy B on alloy A with multiple different melting points, wherein the melting point of alloy A is higher than that of alloy B.

[0036] S2. Conduct a load-bearing study on the alloy pads to determine the required compressive strength;

[0037] S3. Design the composition of the alloy pad;

[0038] S4. Conduct smelting industrial design for the alloy pad and begin smelting.

[0039] The laboratory studied the bonding principle, determined the performance indicators of the pads to be produced, and proposed a manufacturing plan for the pads.

[0040] Step S1 also includes:

[0041] S11. Heat the alloy A and the alloy B to the melting point temperature of the alloy B respectively;

[0042] S12. Pour molten alloy B onto the surface of alloy A and cool to room temperature;

[0043] S13. Measure the atomic penetration depth on alloy A after cooling;

[0044] S14. Determine the melting point of the alloy pad based on the melting point of alloy A with an atomic penetration depth of 0 mm.

[0045] Research has revealed that the principle of electric welding is as follows: the high temperature generated by the discharge melts the metal to form a molten pool, and the molten metals penetrate each other to complete the fusion welding. If a high-melting-point and high-strength alloy is used to make the pad, the iron oxide scale will not adhere to the surface of the pad and thus form a nodule.

[0046] The laboratory used various alloys A and B with different melting points to conduct experiments at high temperatures. Depending on the type of alloy A, the melting point of A was 100℃, 200℃, 300℃, 400℃ and 500℃ higher than that of B.

[0047] By weight percentage, the FeO content in alloy B is ≥90%.

[0048] Steps S2 and S3 include: determining the required compressive strength and designing the composition of the alloy pad based on the current process requirements of the heating furnace.

[0049] Furthermore, A and B were simultaneously heated to the melting point of B, and then B was poured onto the surface of A. After cooling to room temperature, the surface was tapped and observed. The atomic penetration depth of alloy A was obtained by electron microscopy. Specific data are shown in Table 1 below.

[0050] Table 1. Penetration depth of A atoms at different melting point differences

[0051]

[0052]

[0053] Given that FeO has a melting point of only 1369℃ and a softening temperature of 1280℃, experimental results show that when the melting point difference between alloys A and B reaches 300℃, electron microscopy reveals that atoms in A do not show any penetration. Therefore, through experiments, it is determined that a high-temperature heat-resistant alloy with a melting point of at least 1600℃ is required.

[0054] In order to obtain alloy pads that can achieve the required compressive strength, the load-bearing capacity of alloy pads for heating furnaces was studied. According to the current process, for heating furnaces with a load-bearing requirement of 8-12 MPa, in order to ensure that cracks caused by extrusion do not appear on the surface of the steel billet, the compressive strength of the alloy pads must be ≥33 MPa.

[0055] In order to design an alloy composition with more suitable comprehensive performance based on the characteristics of alloy pads, for heating furnaces with a heating range of 0-1350℃, the composition design can be carried out by the V and Ti micro-alloying process route. Micro-alloying refers to adding an appropriate amount of chemical composition to the traditional low alloy high strength structural steel. The specifications clearly list one or more micro-alloying alloying elements that need to be added.

[0056] Analysis revealed the following components and their corresponding contents, with the following weight percentage composition: V 2-12%, Ti 1-3%, Co 20-50%, Cr 50-60%, Ni 10-30%, Mo 5-8%, Al 2-5%, and the remainder being Fe and unavoidable impurities, as detailed in Table 2.

[0057] Table 2. Alloy composition and content

[0058]

[0059]

[0060] After determining the components and their contents, the melting point of the alloy spacer can also be determined based on the above data. The empirical formula is as follows:

[0061] (1) Empirical formula for calculating the melting point of iron-based alloys

[0062] T 熔 =1535-65〔C〕-30〔P〕-25〔S〕-20〔Ti〕-8〔Si]-7〔Cu〕-5〔Mn〕

[0063] -2.5〔Ni〕-2.7〔Al〕-2〔V〕-1.7〔Mo〕-1.5〔Cr]-1.7〔Co〕-1〔 W]-1300[H]-90[N]-80[B]-80[O]-5[Ce]-6.5[Nb]℃ (liquidus);

[0064] (2) Empirical formula for calculating the melting point of nickel-based alloys

[0065] T 熔 =1453-61.7〔C〕-13.2〔Si〕-3.6〔Mn〕-32.3〔S]-35〔P〕-1.6〔Cr〕

[0066] -5[Al]-11.1[Ti]-0[Co]-6.8[Nb]-2.7[W]-1.0[Mo]-0.6[V]-0.75[ Fe]-2.1[Cu]-66.5[B]-5.3[Zr]-62.5[O]-2.7[Mg]-5.9[Ce]℃ (liquidus);

[0067] (3) Empirical formula for calculating the melting point of cobalt-based alloys

[0068] T 熔 =1494-66.8〔C〕-16.7〔Si〕-6.25〔Mn〕-8.3〔Ce〕-2.17〔Cr]-0

[0069] [W]-1.25[Mo]-18.8[Zr]-3.75[V]-10[Ti]-10[Al]-8.7[La]-1.87[Fe]-0.4 5[Ni]-3.3[Cu]-191.3[O]-41.1[P]-35[S]-11[Mg]-12.7[Nb]-40[B]℃ (liquidus line).

[0070] Furthermore, the Co content is controlled with a deviation of ±5% depending on the different pad grades.

[0071] Currently, there are no fixed standards in the industry, so ±5% control can be made based on the grade of the alloy product to reduce deviation.

[0072] Furthermore, Co, Cr, Ni, and Al are all sourced in industrial-grade purity, with a content of 99.99% or higher. Raw materials of industrial purity or higher can yield higher-quality alloy pads.

[0073] Furthermore, after determining the composition and content, the smelting is carried out in a vacuum electric furnace with a vacuum degree of 5-7 MPa, and the final smelting temperature is 100-300°C higher than the highest melting point temperature of the added alloy.

[0074] Under the premise of smelting the base material, the order of addition of each alloying element is Ni, Cr, Co.

[0075] Furthermore, embodiments of the present invention also disclose an alloy pad for a large walking beam furnace, which is manufactured using any of the preparation methods described above.

[0076] By using the above-mentioned element content, composition, and order of addition, and after the corresponding process, an alloy with the above-mentioned compressive strength and melting point can be obtained, thus obtaining a high-strength and high-melting-point alloy pad.

[0077] Chromium can improve the strength of steel, increase its hardenability, and has a secondary hardening effect. However, excessive chromium content will reduce the plasticity and toughness of steel, as well as its weldability. Therefore, the chromium content should be controlled between 50% and 60%.

[0078] Example 1

[0079] A domestic steel rolling mill, with an annual steel production of 2.2 million tons, uses traditional heating furnace high-temperature alloy pads and anti-nodulation technology. The oxidation loss rate is 1.05%, and the gas consumption is 1.68 GJ / t steel. Moreover, iron oxide scale nodules often puncture the pads, resulting in a decrease in the yield of the final product.

[0080] Upon recommendation, this invention is used to replace the pad.

[0081] Based on the technical solution, the specific implementation steps of the present invention are as follows:

[0082] (1) Welding principle of electric welding: The high temperature generated by the discharge melts the metal to form a molten pool. The molten metals penetrate each other to complete the fusion welding. If a high melting point and high strength alloy is used to make the pad, the iron oxide scale will not stick to the surface of the pad and thus form a nodule.

[0083] (2) The laboratory used a variety of alloys A (silicon-manganese alloy, high carbon ferrochrome, medium carbon ferrochrome) and B (FeO) with different melting points to conduct experiments at high temperatures. The melting point of A is greater than that of B by 100, 200, 300, 400 and 500.

[0084] Furthermore, A and B are heated simultaneously to the melting point of B, then B is poured onto the surface of A, cooled to room temperature, and observed by tapping.

[0085]

[0086]

[0087] Therefore, it can be determined that a high-temperature heat-resistant alloy with a melting point of over 1600℃ is required.

[0088] (3) Regarding the load-bearing capacity of the pads used in the heating furnace, according to the current process, the compressive strength of the pads is ≥33Mpa;

[0089] (4) Accordingly, the composition design can be carried out using the V and Ti microalloying process route, and the content of each component is shown in the table below:

[0090] Serial Number symbol content / % 1 V 4 2 Ti 2 3 Co 20 4 Cr 50 5 Ni 12 6 Mo 6 7 AL 3 8 Fe 1

[0091] Furthermore, the Co content is controlled within a deviation of ±5% depending on the different pad block grades;

[0092] Furthermore, Co, Cr, Ni, and Al are all produced in industrial-grade pure form, with a content of 99.99% or higher.

[0093] The melting is carried out in a vacuum electric furnace with a vacuum degree of 5-7 MPa. The final melting temperature is 100-300°C higher than the highest melting point temperature of the added alloy.

[0094] Under the premise of smelting the base material, the order of addition of each alloying element is Ni, Cr, Co.

[0095] By implementing this invention, the steel consumption per ton was reduced to 1.53 GJ / t. With the reduction in heating time, the oxidation loss decreased by 0.05, thus the benefits of implementation are:

[0096] The project will generate 2 million tons of output, contributing 0.6% to the total output.

[0097] The advantages are specifically manifested in:

[0098] (1) Reduced gas consumption per unit (lower temperature, shorter furnace time)

[0099] (Unit consumption before implementation - Unit consumption after implementation) × Output benefited by this process × Material price × Technology contribution - R&D investment. In addition, the unit consumption of coal gas was reduced from 1.68 GJ / t to 1.53 GJ / t, and the price of 1 GJ of mixed coal gas was 28 yuan.

[0100] Benefit: W1 = (1.68 - 1.53) * 28 * 0.6 * 220 = 5,544,000 yuan

[0101] (2) Improve yield (reduce oxidation loss)

[0102] Burn loss reduction × output benefited by this process × (raw material price - waste recycling value) × technology contribution - R&D investment

[0103] Burn loss decreased by 0.03%, and the price difference between sheet metal and genuine products was 2000 yuan / ton. Benefit: W2 = (0.05 * 220) / 100 * 2000 * 0.6 = 1.32 million yuan.

[0104] The project's estimated profit during the implementation period is W = W1 + W2 = 554.4 + 132 = 686.4 million yuan.

[0105] It should be noted that the components or steps in the above embodiments can be interchanged, substituted, added, or deleted. Therefore, the combinations formed by these reasonable permutations and transformations should also fall within the protection scope of this invention, and the protection scope of this invention should not be limited to the above embodiments.

[0106] The above are exemplary embodiments disclosed in this invention. The order of the disclosed embodiments is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. However, it should be noted that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the disclosed embodiments of this invention (including the claims) is limited to these examples. Various changes and modifications can be made without departing from the scope defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular.

[0107] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of the different aspects of the invention as described above exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for preparing alloy pads for large walking beam furnaces, characterized in that, Includes the following steps: S1. The melting point of the alloy pad is determined based on the atomic penetration depth of FeO-containing alloy B on alloy A with various melting points, wherein the melting point of alloy A is higher than that of alloy B, and the melting point of the alloy pad is determined based on the melting point of alloy A with an atomic penetration depth of 0 mm; by weight percentage, the FeO content in alloy B is ≥90%; S2. Conduct a load-bearing study on the alloy pads to determine the required compressive strength; S3. Design the composition of the alloy pad; S4. Conduct smelting industrial design for the alloy pad and begin smelting; For steel billets in heating furnaces with a load-bearing requirement of 8-12 MPa, the compressive strength of the alloy pad is ≥33 MPa; For heating furnaces with a heating range of 0-1350℃, a V and Ti micro-alloying process is adopted for composition design. The alloy pad has the following weight percentage composition: V 2-12%, Ti 1-3%, Co 20-50%, Cr 50-60%, Ni 10-30%, Mo 5-8%, Al 2-5%, with the remainder being Fe and unavoidable impurities. The smelting is carried out in a vacuum electric furnace with a vacuum degree of 5-7 MPa, and the final smelting temperature is 100-300°C higher than the highest melting point temperature of the added alloy. Step S1 includes: S11. Heat the alloy A and the alloy B to the melting point temperature of the alloy B respectively; S12. Pour molten alloy B onto the surface of alloy A and cool to room temperature; S13. Measure the atomic penetration depth on alloy A after cooling; S14. Determine the melting point of the alloy pad based on the melting point of alloy A with an atomic penetration depth of 0 mm.

2. The preparation method according to claim 1, characterized in that, The Co content is controlled with a deviation of ±5% depending on the grade of the alloy pad. The Co, Cr, Ni and Al are all industrially pure and have a content of 99.99% or higher.

3. The preparation method according to claim 2, characterized in that, Under the premise of smelting the base material, the order of addition of each alloying element is Ni, Cr, Co.

4. An alloy pad block for a large walking beam furnace, characterized in that, It is prepared by the preparation method described in any one of claims 1-3.

Images