Grid section material for sintering machine trolley, grid section manufacturing method and long-service-life grid section

Abstract

The invention discloses a grate bar material for a sintering machine trolley, a grate bar manufacturing method and a long-life grate bar. The grate bar material comprises the following chemical elements in percentage by mass: 1.2-1.6% of C, 25-29% of Cr, 0.4-0.8% of Mn, 0.8-1.2% of Si, 1.5-2.0% of Ni, greater than or equal to 0.5% of Mo, 0.1-0.2% of V, 0.15-0.2% of heavy rare earth HREE, 0.5-0.8% of Re and the balance of Fe and inevitable impurities. Through optimal design of a grate bar material formula and a pouring process and redesign of a grate bar structure, the grate bar manufactured by adopting the formula and the process has good high temperature resistance, fatigue resistance, corrosion resistance and self-cleaning performance, the red hardness performance of the grate bar is greatly improved, the service life can be prolonged by more than two times, and the service life of the grate bar is prolonged by more than two times. And the downtime and the maintenance cost of the sintering machine are reduced.

Description

Technical Field

[0001] The invention particularly relates to a grate material for a sintering machine trolley, a grate manufacturing method and a long-life grate, and belongs to the technical field of steelmaking. Background Art

[0002] Iron ore sintering is a crucial step in steelmaking. During roasting, the iron ore, auxiliary fuel, flux, and water are uniformly mixed and stirred in a specific proportion. The ore is then evenly spread onto a sintering trolley to a desired thickness. Natural gas is injected to a temperature of approximately 1100°C, sintering the trolley into pellets or briquettes for use in the ironmaking furnace. The sintering machine trolley grate is a core component, directly supporting the combustion of the ore. The grate's ventilation directly impacts sintering output and production costs. The grate's service life and natural wear directly affect the frequency and duration of trolley maintenance, as well as labor intensity. The sintering process operates in an extremely harsh environment, with temperatures reaching as high as 1150°C. This requires high red hardness and fatigue resistance, otherwise the grates will deform, primarily manifesting as warping on the sides and arching in the center. As the trolley operates and the sintering material is unloaded, the heating temperature continuously cycles between approximately 150°C and 900°C. The flue gas generated by the ore during the sintering process contains large amounts of SO2, NOx, CO2, and water vapor. These flue gases, at high temperatures, are highly corrosive to the grate bars. In recent years, with increasing environmental pressure, some steel mills have been adding auxiliary materials such as chimney ash and industrial wastewater to the sintering material before stirring and sintering. This has caused elevated concentrations of pollutants such as ultrafine particulate matter (PM10, PM2.5), alkali (heavy) metals (K, Na, Pb, Zn), and SO2 in the sintering flue gas, exacerbating the corrosion of the grate bars and causing them to become "sticky" and clogged, impacting ventilation.

[0003] To ensure a smooth sintering process, the grate bars used in sintering carts must not only have excellent ventilation but also possess resistance to high temperatures, fatigue, corrosion, and wear, as well as high red hardness at high temperatures. Currently, high-chromium cast iron, known for its high-temperature and corrosion-resistant properties, is widely used as the primary raw material for these bars. These bars typically contain high levels of chromium and carbon, but their performance can be enhanced by adding varying amounts of elements such as nickel, molybdenum, copper, niobium, vanadium, and rare earth elements. For example: The Chinese patent document with publication number CN 119194291 A, publication date December 27, 2024, and titled “A sintering machine trolley grate bar and its manufacturing method” discloses a high chromium alloy for sintering machine trolley grate bars and its manufacturing method, the main chemical components (wt%) of which are the following elements: C = 0.70-1.00%, Si = 1.5-2.5%, Mn = 0.20-0.4%, S ≤ 0.03%, P ≤ 0.03%, Cr = 18-21%, Mo = 0-0.5%, RE = 0.010-0.025%, and the balance is Fe and unavoidable impurities.

[0004] The grate composition currently in common use still has some problems in practical application. If the amount of alloying elements added is small, the corrosion resistance of the obtained grate is insufficient and the corrosion is serious during use. The element ratio design is unreasonable and the high temperature resistance is poor. For example, the ratio of Cr to C is not coordinated, and a large amount of Cr7C3 compounds are easily formed in the cast material. These compounds may form a network and distribute at the grain boundaries, which will not only reduce the effective Cr content in the matrix, but also affect the material's resistance to intergranular corrosion, thereby significantly reducing the material's corrosion resistance and affecting the material's service life. In addition, existing grate bars (such as Figure 8 The structural design of the fan (as shown) is also not very reasonable. For example, its top surface is flat, which is prone to accumulation of materials and causes blockage, affecting the ventilation effect and heat dissipation. It is easy to deform during use, which ultimately shortens its lifespan. Summary of the Invention

[0005] In view of the shortcomings and defects in the prior art, the present invention provides a grate material, a grate manufacturing method and a long-life grate for a sintering machine trolley. It is expected that the grate bars manufactured using the grate material will have at least one of the following excellent properties, such as high temperature resistance, fatigue resistance, corrosion resistance, self-cleaning, good high-temperature red hardness, etc., which can greatly extend the service life of the grate bars.

[0006] The technical solutions of the present invention are as follows: A grate material for a sintering machine trolley contains the following chemical elements in percentage by mass: C: 1.2-1.6%, Cr: 25-29%, Mn: 0.4-0.8%, Si: 0.8-1.2%, Ni: 1.5-2.0%, Mo: ≧0.5%, V: 0.1-0.2%, heavy rare earth HREE: 0.15-0.2%, Re: 0.3-0.5%, and the balance is Fe, unavoidable impurities and other substances.

[0007] Furthermore, the HREE is Y (yttrium).

[0008] The present invention also provides a method for manufacturing grate bars, comprising the following steps: (1) Material preparation: Arrange the required raw materials in a certain order and quantity; (2) Add a certain amount of scrap steel into the medium frequency furnace, turn on the heating and melt it; (3) Add high carbon ferrochrome and low carbon ferrochrome into the medium frequency furnace in a certain proportion, first add high carbon ferrochrome and then add low carbon ferrochrome; (4) Add a certain amount of nickel plate, ferromolybdenum and ferrovanadium into the medium frequency furnace; (5) Continue to raise the temperature to 1650 degrees and add appropriate amount of ferromanganese; (6) Continue to heat up to 1680 degrees, add appropriate amount of ferrosilicon; skim off the slag; continue to heat up to 1700 degrees; (7) Prepare the ladle, add appropriate amount of yttrium-based heavy rare earth alloy and rhenium-iron alloy into the ladle, then pour the molten steel in the medium frequency furnace into the ladle, and skim the slag twice; sprinkle a layer of slag-collecting insulation agent evenly into the ladle, let it stand for 3 minutes; cover it with slag-blocking cotton and prepare for pouring; (8) Turn on the vacuum pump, evacuate the sand box with the grate model embedded in it, and pour under negative pressure. After pouring, sprinkle the riser insulation agent on the riser; keep it warm for more than 10 hours before turning the box over; after turning the box over, take the test piece for element analysis to ensure that the composition of each element meets the above ratio; (9) The grate bars are placed in a drum for sand cleaning after being taken out of the box. After the sand cleaning is completed, they are bundled and stored in the warehouse to obtain the finished grate bars.

[0009] The design principles of each chemical element in the grate material are as follows: C: In the ultra-long-life, acid- and alkali-resistant, self-cleaning grate material for sintering machine trolleys described in the present invention, C is the main element affecting the strength and toughness of the alloy. It plays a core role and is also the most important alloying element, determining the basic classification, microstructure, and ultimate mechanical and processing properties of steel. Without carbon, there is no real steel. It is also the main element that improves the high-temperature strength of the matrix. When the C content in the steel is too low, the strength and heat resistance of the material cannot be guaranteed; when the C content in the steel exceeds 0.6%, the hardness of the material will increase significantly, and the plasticity and toughness of the steel will decrease significantly. When the C content in the steel exceeds 0.9%, although the hardness still increases, the excessive carburized material will split the pearlite structure, resulting in a decrease in the overall strength of the material. The carbon content is a key factor affecting the hardness of the material. The higher the carbon content, the smaller the grain size and the greater the number of grain boundaries. The higher the strength of the steel, the lower its plastic deformation ability and the worse its corrosion resistance. Elemental carbon can form M7C3 carbides with chromium, leading to excessive consumption of chromium in the material, reducing the chromium content. Furthermore, this reduced chromium content can increase the risk of intergranular corrosion. Therefore, in the ultra-long-life, acid- and alkali-resistant, self-cleaning sintering machine grate material described herein, the mass percentage of elemental carbon is controlled between 1.2% and 1.6%.

[0010] Cr: In the grate material for sintering machine trolleys with ultra-long life, acid and alkali resistance, and self-cleaning function described in the present invention, Cr is the rust-proof guard and high-temperature shield in the alloy, plays a cornerstone role, and is also the main alloying element in alloy steel. Chromium in the alloy can increase its hardenability and secondary hardening effect, and improve the wear resistance of carbon steel without making the material brittle. When the chromium content in the material reaches more than 25%, chromium-containing carbides are formed, and the chromium atoms dissolve in the ferrite or austenite matrix. Since their atomic size is different from that of iron atoms, it causes lattice distortion, hinders dislocation movement, and thus improves the strength and hardness of the material. Chromium can delay the transformation of austenite to pearlite and bainite, but needs to be used in combination with other elements with high hardenability: such as: Mn, Mo, and Ni. When the Cr content in the alloy exceeds 10.5%, it forms carbides with carbon and forms a dense chromium oxide passivation film (Cr2O3) on the surface. Because this chromium passivation film (Cr2O3) is unreactive with most chemicals, it effectively prevents oxygen from diffusing into the material, significantly improving the material's oxidation resistance in high-temperature environments and extending its service life. While adding higher amounts of Cr can effectively enhance the material's high-temperature and corrosion resistance, the improvement is insignificant when the Cr content exceeds 30%. Therefore, in the high-corrosion-resistant grate bar material described herein, the Cr content is controlled between 25% and 29% by weight.

[0011] Mn: In the grate material for sintering machine trolleys with ultra-long life, acid and alkali resistance, and self-cleaning function described in the present invention, Mn is a transition metal in the material, and its functions include (1): deoxidation, desulfurization, purification of molten steel, and elimination of hot brittleness. It can absorb a large amount of oxygen in molten steel, improving the purity of steel. Manganese has a stronger affinity with sulfur than iron, forming manganese sulfide that can be distributed in molten steel, thereby eliminating or reducing hot brittleness. (2): Mn can be dissolved in ferrite (a-Fe) or austenite (y-Fe). The size of manganese atoms is significantly different from that of iron atoms, hindering dislocation movement, thereby improving the strength and hardness of the material. (3) Manganese is a strong austenite-forming element, which can completely inhibit the transformation of austenite to ferrite and pearlite at room temperature, maintaining a single austenite structure. However, it should be noted that the Mn content in steel should not be too high. Excessive Mn content in steel is not conducive to austenite transformation and interferes with the formation of the anti-oxidation chromium passivation film (Cr2O3). Therefore, considering the influence of Mn on the material properties, in the present invention, the mass percentage of Mn is controlled to be between 0.4% and 0.8%.

[0012] Si: In the ultra-long-life, acid- and alkali-resistant, self-cleaning grate material for sintering machine trolleys described herein, Si has a stronger deoxidizing ability than manganese. During steelmaking, it preferentially combines with oxygen to form SiO2, reducing the oxygen content in molten steel. This improves the fluidity of molten steel and reduces casting defects. It enhances ferrite strength through solid solution strengthening, increases resistivity and magnetic permeability, promotes graphitization, and increases austenite stability. It can improve the morphology of eutectic carbides and enhance microstructure uniformity. Adding an appropriate amount of Si to steel can also increase the matrix electrode potential and enhance corrosion resistance. However, as the Si content in steel increases, the brittleness of the material increases when Si exceeds 0.6%, necessitating the addition of appropriate amounts of Ni and Mo to compensate. Therefore, excessive Si addition to steel is not advisable. Therefore, in the highly corrosion-resistant grate material described herein, the mass percentage of Si is controlled between 0.8% and 1.2%.

[0013] Ni: In the grate bar material for sintering machine trolleys with ultra-long life, acid and alkali resistance and self-cleaning function described in the present invention, Ni is known as the king of toughness, and Ni and Cr are irreplaceable golden partners. The complementary relationship between Ni and Cr: Cr provides a corrosion-resistant shield, and Ni is the protector of toughness. Adding an appropriate amount of Ni element to the Cr-containing iron alloy can improve the stability of the matrix austenite, reduce the ductile-brittle transition temperature, and help improve corrosion resistance. Ni can increase the ductility of steel, withstand greater plasticity when under stress and is not easy to break. The combination of Ni and Cr greatly enhances the corrosion resistance of the alloy and promotes the formation and stability of the passivation film. Based on this, in the grate bar material for sintering machine trolleys with ultra-long life, acid and alkali resistance and self-cleaning function described in the present invention, the mass percentage of Ni element is controlled between 1.5 and 2.0%.

[0014] Mo: In the ultra-long-life, acid- and alkali-resistant, self-cleaning grate material for sintering machine trolleys described herein, Mo plays an irreplaceable role in alloy steel, improving its high-temperature strength and corrosion resistance. The carbides of Mo and Cr in alloy steel differ, with Mo carbides being finer and more stable at high temperatures. Mo in alloy steel preferentially forms MoO2, promoting the self-healing ability of the passivation film in a chloride ion environment while inhibiting chloride ion penetration, significantly improving pitting corrosion resistance. In high-temperature environments, Mo atoms (atomic radius greater than iron) severely distort the crystal lattice, hindering high-temperature dislocation movement. The resulting stable carbides (Mo2C / Mo6C) pin grain boundaries and inhibit high-temperature grain boundary sliding, doubling the high-temperature endurance strength. Mo combined with Cr can repair defects in the Cr2O3 film, increasing pitting corrosion resistance by a factor of four. Therefore, given the significant impact of Mo on production costs, the Mo content in the highly corrosion-resistant grate material described herein is ≥ 0.5%.

[0015] V: In the ultra-long-life, acid- and alkali-resistant, self-cleaning grate material for sintering pallets described herein, the element V has a strong affinity with carbon and nitrogen in the alloy, forming fine, dispersed, and highly stable carbides (VC) and nitrides (VN). These fine carbides and nitrides pin grain boundaries during high-temperature austenitization, strongly hindering austenite grain growth and inhibiting high-temperature deformation (creep). This helps delay fatigue crack initiation and propagation, thereby improving the fatigue resistance of the alloy steel. However, in high-temperature environments, a V content exceeding 0.2% can reduce material strength and lead to fracture. Therefore, in the corrosion-resistant grate material for sintering pallets described herein, the V content is controlled between 0.1% and 0.2% by weight.

[0016] Sulfur (S) is an unavoidable impurity element in the ultra-long-life, acid- and alkali-resistant, self-cleaning grate bars for sintering carts described herein. S forms non-metallic inclusions (MnS and FeS) with the manganese and iron elements in the material, reducing the material's ductility and fatigue strength. Sulfides on the material's surface can easily become corrosion initiation points, accelerating localized corrosion. To achieve higher-performance and higher-quality materials, the S content should be minimized to 0.035% or less.

[0017] P: In the ultra-long-life, acid- and alkali-resistant, self-cleaning grate bars for sintering pallets described in this invention, P is an unavoidable impurity element in alloy steel. Every 0.01% increase in P increases the ductile-brittle transition temperature by 20-25°C. To achieve higher-performance and higher-quality corrosion-resistant grate bars for sintering pallets, the P content in the steel should be minimized.

[0018] Re: In the ultra-long-life, acid- and alkali-resistant, self-cleaning grate material for sintering machine trolleys described herein, rhenium further enhances the material's strength, hardness, corrosion resistance, and wear resistance, creating a "rhenium effect." This refines the material's microstructure, reduces grain size, and improves its mechanical properties. The addition of an appropriate amount of rhenium improves the material's thermal fatigue cycling at high temperatures. The addition of rhenium also increases the activity of Cr, which promotes the self-healing of the Cr2O3 film, prolonging its lifespan and enhancing the material's high-temperature oxidation and corrosion resistance. The rhenium content in the grate material of this invention is controlled to 0.3-0.5%.

[0019] Y: In the ultra-long-life, acid- and alkali-resistant, self-cleaning grate material for sintering machine trolleys described herein, the heavy rare earth element yttrium significantly improves the material's oxidation resistance, particularly at high temperatures, where it forms a continuous, dense oxide film, enhancing the material's hardness and strength. Yttrium also refines the as-cast structure, enhancing the material's fatigue and creep resistance, improving corrosion resistance, and extending the material's service life. The yttrium content in the grate material of this invention is controlled to 0.15-0.2%.

[0020] Adding an appropriate amount of rhenium and yttrium heavy rare earth alloy in a certain proportion can inhibit the formation of metal compounds, promote disordered solid solution, refine the secondary grains of the material, and strengthen the chromium oxide passivation film (Cr2O3), greatly improving the high temperature resistance, acid and alkali resistance, and fatigue resistance of the grate bars. At the same time, it improves the red hardness of the grate bars, essentially eliminating the problem of grate bar deformation and greatly increasing the service life of the grate bars. In the present invention, through the synergistic effect of multiple elements, the passivation corrosion resistance is significantly improved. The atomic structure of the grate bar alloy material in the present invention is close to that of high entropy alloys. Due to the change in its microstructure, its performance far exceeds that of traditional grate bar alloy materials.

[0021] The present invention also provides a long-life grate bar for a sintering machine, comprising a long strip-shaped body, an upper support structure, and a lower support structure, characterized in that a cylindrical crossbeam is arranged on the top surface of the long strip-shaped body along the length direction, and an upper support structure is provided at each end of the crossbeam. The two upper support structures are arranged symmetrically, and the upper surface of the upper support structure is arched. The outer side of the upper support structure extends out of the long strip-shaped body to form an upper support arm, and the inner side of the upper support structure is located above the long strip-shaped body and transitionally connected to the crossbeam. The highest point of the upper support structure is higher than the crossbeam.

[0022] Furthermore, the cross-section of the upper support arm includes an upper arc surface, a left vertical surface, a right vertical surface, a left inclined surface, a right inclined surface, and a lower plane, wherein the left vertical surface and the right vertical surface are vertical planes, which are symmetrically arranged, and the distance between the left vertical surface and the right vertical surface is greater than the diameter of the cross-section of the beam; the left inclined surface and the right inclined surface are inwardly inclined planes, which are symmetrically arranged, and the lower plane is a horizontal plane.

[0023] Furthermore, reinforcing ribs are provided on both sides of the front and rear sides of the long strip body, the upper part of the reinforcing ribs is connected to the left or right facade of the upper support arm through an air guide slope, and the lower part of the reinforcing ribs extends to the end of the lower support structure.

[0024] Furthermore, lower support structures are respectively provided at the left and right ends of the bottom surface of the elongated body, and the two lower support structures are symmetrically arranged. The bottom of the lower support structure extends outward to form a lower support arm, and the inner upper surface of the lower support arm is an arc-shaped surface. The length of the lower support arm is smaller than the length of the upper support arm. The upper support arm, the lower support arm, and an outer side surface of the elongated body located on the same side of the elongated body constitute a semi-enclosed support structure.

[0025] Furthermore, a heat insulation pad is provided in the center of the inner side of the vertical surface of the semi-enclosed support structure.

[0026] Furthermore, at least one spacer block is provided at corresponding positions on the front and rear sides of the elongated body, the two spacer blocks at corresponding positions on the front and rear sides are symmetrically arranged, and the distance between the outer facades of the two spacer blocks at corresponding positions on the front and rear sides is greater than the diameter of the beam.

[0027] Furthermore, the diameter of the cross section of the beam is greater than or equal to the thickness of the top surface of the elongated body, the thickness of the top surface of the elongated body is greater than the thickness of its bottom surface, and the front side and the rear side of the elongated body are symmetrically arranged.

[0028] Beneficial effects: The present invention optimizes the grate material formula and casting process, so that the grate made with the formula has good high temperature resistance, fatigue resistance, and corrosion resistance, greatly improving the red hardness of the grate; at the same time, the grate structure is redesigned, with significant anti-blocking effect, self-cleaning performance, better ventilation effect, and stronger high-temperature deformation resistance; the grate formula process and structure of the present invention can work alone to improve the production of traditional grate bars and improve their performance and service life; of course, the formula process and structure can also be combined to work together. When the grate bars are made with the formula process and structure of the present invention, the service life can be increased by more than two times compared with the grate bars in the prior art under the same use conditions, which significantly reduces the downtime and maintenance costs of the sintering machine and improves the production efficiency and benefits of the enterprise. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the three-dimensional structure of the grate bar of the present invention.

[0030] Figure 2 It is a front view of the grate bar of the present invention.

[0031] Figure 3It is a left side view of the grate bar of the present invention.

[0032] Figure 4 It is a top view of the grate bar of the present invention.

[0033] Figure 5 yes Figure 2 AA section view in.

[0034] Figure 6 It is a schematic diagram of the installation and use status of the grate bars of the present invention.

[0035] Figure 7 yes Figure 6 Top view of .

[0036] Figure 8 It is a grate bar structure in the prior art.

[0037] Markings in the figure: 1 long strip body, 2 cylindrical crossbeam, 3 upper supporting structure, 4 lower supporting structure, 5 boss, 6 wind guide slope, 7 reinforcing rib, 8 spacer support block, 9 insulation pad support beam, 10 ventilation gap, 31 upper support arm, upper arc surface 311, left vertical surface 312, right vertical surface 313, left inclined surface 314, right inclined surface 315, lower plane 316, 41 lower support arm, 411 arc surface. DETAILED DESCRIPTION

[0038] Example 1 - Method for manufacturing grate bars The production of grate bars primarily involves two steps: smelting and casting. First, prepare the raw materials: place them in a specific order and quantity. Adding them out of order will prolong the smelting process and increase power consumption. This will not only fail to extend the life of the grate bars, but may also lead to serious quality issues.

[0039] 1. Add 500kg of scrap steel into the smelting medium frequency furnace and heat it to about 1400 degrees to melt it; the melting point of scrap steel is low, it can melt quickly, reducing the melting time, effectively reducing power consumption, and facilitating the addition and melting of subsequent materials.

[0040] 2. First, add 180kg of high-carbon ferrochrome (carbon content 8%) into the medium-frequency furnace, and then add 270kg of low-carbon ferrochrome into the medium-frequency furnace and heat to about 1450 degrees to melt. Since the price of low-carbon ferrochrome is nearly twice that of high-carbon ferrochrome, and high-carbon ferrochrome will burn out the carbon element in the ferrochrome in a long-term high-temperature environment, in this example, the combination of high-carbon ferrochrome and low-carbon ferrochrome can reduce the raw material cost of ferrochrome.

[0041] 3. Add 20kg nickel plate, 9kg ferromolybdenum and 4kg ferrovanadium into the medium frequency furnace at the same time and continue heating to about 1500 degrees to melt.

[0042] 4. When the molten iron temperature reaches 1650 degrees, add 13kg of ferromanganese. Because manganese and sulfur can only form MnS when the molten steel reaches above 1610 degrees, it can avoid the formation of FeS and reduce the brittleness of the material. At the same time, manganese reacts with FeO in the molten steel to form MnO, which plays a deoxidation and desulfurization role, enhances the hardness and wear resistance of the material, and purifies the molten steel.

[0043] 5. Continue to heat up to 1680 degrees and add 18kg of ferrosilicon and skim off the slag; because ferrosilicon is a good deoxidizer, it can significantly reduce bubbles and impurities in the molten steel when combined with oxygen to produce SiO2, thus purifying the molten steel.

[0044] 6. Prepare the molten iron ladle and put 3.5kg of yttrium-based heavy rare earth alloy and 7kg of rhenium-iron alloy into the molten iron ladle; do not put the yttrium-based heavy rare earth alloy and rhenium-iron alloy directly into the molten steel of the medium frequency furnace for smelting to prevent decay and ineffectiveness.

[0045] 7. When the temperature of the molten steel reaches 1700 degrees, the molten steel can be poured into the ladle; the speed of pouring the molten steel into the ladle should be appropriately faster so that the molten steel rolls in the ladle and the yttrium-based rare earth alloy and rhenium-iron alloy in the ladle are evenly fused.

[0046] 8. After pouring the molten steel, skim off the slag for the second time and evenly sprinkle a layer of slag-aggregating insulation into the ladle. Let it stand for 3 minutes to allow the yttrium-based rare earth alloy and rhenium-iron alloy in the ladle to fully fuse and reduce the oxygen content of the molten steel.

[0047] 9. After the molten steel has been still for 3 minutes, cover the outlet of the ladle with slag cotton and start pouring. The lost foam process is used for pouring, and a grate model is placed in the sandbox in advance.

[0048] 10. Turn on the vacuum pump and evacuate the sand box with the pre-embedded grate pattern for negative pressure pouring. When pouring the molten steel, follow the principle of pouring slowly at first, then quickly in the middle, and then slowly at the end to prevent the molten steel from choking. Complete the pouring within 10 minutes. If the pouring time is too long, the effects of yttrium and rhenium on the material's grain refinement, antioxidant capacity enhancement, and high-entropy alloy formation will diminish, and the material's performance improvements will no longer be apparent. The mechanism of this decline is currently unclear, but it can be compared to the decline of spheroidization in ductile iron production.

[0049] 11. After pouring, sprinkle riser insulation agent on the riser, keep it warm for more than 10 hours before turning the box. After turning the box, take the test block for element analysis to ensure that the composition of each element meets the design proportion requirements.

[0050] 12. Put the grate bars out of the box into the drum for sand cleaning. Through the mutual friction and collision between the grate bars, the attachments and burrs on the surface of the grate bars are cleaned.

[0051] 13. After the grate bars are cleaned, they are packed or bundled and stored according to customer requirements.

[0052] Example 2 - Structure of grate bars The grate bars are integrally formed by the casting process described in Example 1, and their structure is as follows: Figure 1-5 As shown, it has two symmetry planes, namely symmetry plane E and symmetry plane F (see Figure 4 ), and the symmetry plane E and the symmetry plane F are perpendicular to each other, and the grate bar includes a long strip body 1, two left and right upper supporting structures 3 and two left and right lower supporting structures 4.

[0053] Specifically, the thickness of the top surface of the long strip body is greater than the thickness of the bottom surface, so that the material can fall smoothly and prevent the material from being blocked. The front side and the rear side of the long strip body are symmetrically arranged, that is, the cross section of the long strip body 1 is an isosceles trapezoid, which is wide at the top and narrow at the bottom (see Figure 5 The lower half of the shaded part in the figure) is provided with a cylindrical crossbeam 2 along the length direction on the top surface of the long strip body, and the diameter of the crossbeam section is greater than or equal to the top surface thickness of the long strip body (see Figure 5 The upper half of the shaded part in the figure), the cylindrical crossbeam can bear greater pressure; an upper support structure 3 is provided at each end of the crossbeam 2, and the two upper support structures are arranged symmetrically. The upper surface of the upper support structure is arched to increase the bearing capacity and prevent the head from deforming due to heat. The outer side of the upper support structure extends out of the long strip body to form a suspended upper support arm 31. The inner side of the upper support structure is located above the long strip body and is transitionally connected to the crossbeam as a whole. The highest point of the upper support structure is higher than the crossbeam (superior to the plane structure of the existing grate, which enhances the bearing capacity and prevents deformation); Figure 3 As shown, the cross-section of the upper support arm includes an upper curved surface 311, a left vertical surface 312, a right vertical surface 313, a left inclined surface 314, a right inclined surface 315, and a lower plane 316. Left and right vertical surfaces 312 and 313 are vertical planes, symmetrically arranged. The distance between them is greater than the diameter of the cross-beam cross-section, which increases ventilation. Left and right inclined surfaces 314 and 315 are inwardly inclined planes, symmetrically arranged. Lower plane 316 is a horizontal plane. Left inclined surface 314, lower plane 316, and right inclined surface 315 are interconnected in sequence to form a frustum (or isosceles trapezoid) structure. During trolley rollover, this structure achieves a material removal rate exceeding 95%, significantly preventing sticking and blocking, significantly reducing the labor and time required to clear sticking, and shortening maintenance time, resulting in significant economic benefits.

[0054] A lower support structure 4 is provided at the left and right ends of the bottom surface of the elongated main body 1, and the two lower support structures are arranged symmetrically. The bottom of the lower support structure extends outward to form a lower support arm 41, and the inner upper surface of the lower support arm is an arc-shaped surface 411 (when the trolley is flipped, the arc-shaped surface is conducive to the left and right shaking of the grate bar, so that the residual material can fall off smoothly to prevent clogging). The length of the lower support arm 41 is smaller than the length of the upper support arm 31. The upper support arm 31, the lower support arm 41, and an outer side surface of the elongated main body on the same side of the elongated main body 1 constitute a semi-enclosed support structure. A boss 5 is provided in the center of the inner side of the vertical surface of the semi-enclosed support structure. The setting of the boss 5 can reduce the contact area between the grate semi-enclosed support structure and the insulation pad support beam 9, increase ventilation, facilitate heat dissipation, extend service life, and facilitate the shedding of fine materials. Reinforcing ribs 7 are provided on both the left and right sides of the front and rear sides of the elongated body. The upper portion of the ribs 7 is connected to either the left or right facade of the upper support arm via an air guide slope 6. The lower portion of the ribs 7 extends along the semi-enclosed support structure to the ends of the front and rear surfaces of the lower support arm 41. The ribs improve the deformation resistance of the entire grate bar.

[0055] Furthermore, at least one spacer block 8 is provided at the corresponding positions of the front side and the rear side of the elongated body 1, and the two spacer blocks 8 at the corresponding positions of the front and rear side are symmetrically arranged. The shape of the spacer block can be circular, semicircular, annular, semicircular, square, triangular, etc. Preferably, the semicircular ring structure with the opening downward can play a spacing role, reduce material costs, and is not easy to clog; in this example, two spacer blocks 8 are provided at the corresponding positions of the front side and the rear side of the elongated body 1, and their shape is circular; the distance between the outer facades of the two spacer blocks at the corresponding positions of the front and rear side of the elongated body 1 is greater than the diameter of the beam and less than the thickness of the upper support arms at both ends, so as to limit the minimum gap between the two grate bars when they are placed close together. Preferably, the outer facade of the spacer block is coplanar with one of the left facade or the right facade of the upper support arm.

[0056] like Figure 6-7 As shown, when the grate bars are in use, multiple grate bars are placed side by side and installed on two parallel and spaced insulation pad support beams 9 of the sintering trolley. At this time, the upper support arms of the grate bars are in contact with the upper surface of the insulation pad support beams. There are ventilation gaps 10 between adjacent grate bars. Multiple trolleys are installed side by side on the guide rails. A layer of sintering material is laid on the grate bars of the trolley in the loading area. The particle size of the sintering material is larger than the gaps between the grate bars. Then the ignition is started and the air is exhausted under negative pressure. After passing through the material layer, the air flow flows through the air guide slope and gaps of the grate bars. The trolley moves along Figure 7It runs forward in the direction of the middle arrow until it reaches the unloading area, where the trolley tilts and turns over, and the material falls freely. At the same time, the grate bars are upside down. When the grate bars are upside down, the lower support arm of the grate bars contacts the lower surface of the insulation pad support beam. Since the inner surface of the lower support arm is set as an arc surface, that is, the arc-shaped lower support arm contacts the insulation pad support beam, the grate bars are in an unstable state. As the trolley runs, the grate bars are free, and the shaking grate bars collide with each other. The sintered materials adhered to the grate bars or between the grate bars can be effectively fallen off, thereby achieving the self-cleaning effect of the trolley grate bars.

[0057] The actual use effect of the grate of the present invention and the grate in the prior art in the sintering machine of Anyang Iron and Steel Group is compared as follows: Product Comparison Service life Drop test (free fall to concrete floor) Blockage during use Deformation during use ventilation performance The existing design of grate bar structure and element formula (excluding yttrium and rhenium) 18-24 months 2 meters high without breaking Easy to lose gambling Easy to deform Average ventilation effect The grate structure and element formula of the present invention (containing yttrium and rhenium) 40 months and above 10 meters high without breaking With self-cleaning function, no clogging Excellent red hardness, will not deform under 1150 degree environment Arc-shaped design with added vents at both ends, increasing air volume by 15% .

Claims

1. A grate material for a sintering machine trolley, characterized in that: It contains various chemical elements in the following mass percentages: C: 1.2-1.6%, Cr: 25-29%, Mn: 0.4-0.8%, Si: 0.8-1.2%, Ni: 1.5-2.0%, Mo: ≧0.5%, V: 0.1-0.2%, heavy rare earth HREE: 0.15-0.2%, Re: 0.3-0.5%, and the balance is Fe and unavoidable impurities.

2. The grate material for a sintering machine trolley according to claim 1, characterized in that: The heavy rare earth HREE is Y (yttrium).

3. A method for manufacturing grate bars, comprising the following steps: (1) Material preparation: Arrange the required raw materials in a certain order and quantity; (2) Add a certain amount of scrap steel into the medium frequency furnace, turn on the heating and melt it; (3) Add high carbon ferrochrome and low carbon ferrochrome into the medium frequency furnace in a certain proportion, first add high carbon ferrochrome and then add low carbon ferrochrome; (4) Add a certain amount of nickel plate, ferromolybdenum and ferrovanadium into the medium frequency furnace; (5) Continue to raise the temperature to 1650 degrees and add appropriate amount of ferromanganese; (6) Continue to heat up to 1680 degrees, add appropriate amount of ferrosilicon; skim off the slag; continue to heat up to 1700 degrees; (7) Prepare the ladle, add appropriate amount of yttrium-based heavy rare earth alloy and rhenium-iron alloy into the ladle, then pour the molten steel in the medium frequency furnace into the ladle, and skim the slag twice; sprinkle a layer of slag-collecting insulation agent evenly into the ladle, let it stand for 3 minutes; cover it with slag-blocking cotton and prepare for pouring; (8) Turn on the vacuum pump, evacuate the sand box with the grate model embedded in it, and pour under negative pressure. After pouring, sprinkle the riser insulation agent on the riser; keep it warm for more than 10 hours before turning the box over; after turning the box over, take the test piece for element analysis to ensure that the composition of each element meets the ratio of each element as described in claim 1; (9) The grate bars are placed in a drum for sand cleaning after being taken out of the box. After the sand cleaning is completed, they are bundled and stored in the warehouse to obtain the finished grate bars.

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