Welding wire for welding repair of nodular cast iron structure of sintering pallet and wind wheel roller and using method of welding wire

Abstract

The invention provides a welding wire for welding and repairing nodular cast iron structures of sintering pallets and wind wheel rollers and a using method of the welding wire. The welding wire comprises the following components of, by mass, 0.03%-0.07% of C, 10%-12% of Cr, 8%-10% of Mn, 0.2%-0.4% of Si, 32%-36% of Ni, 0.6%-0.8% of Nb and the balance Fe and inevitable impurities. The using method comprises the step of welding and repairing the defective part of the sintering pallet structure or the wind wheel roller structure. And the repaired area is well formed, welding defects such as cracks and inclusions do not exist, long-time service of the repaired part can be achieved, and high-efficiency, high-quality and low-cost welding repair of the sintering pallet and the wind wheel rolling shaft is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of ductile iron welding repair materials, and specifically relates to a welding wire for welding and repairing ductile iron structures of a sintering trolley and a wind wheel roller, and a use method thereof. Background Art

[0002] The sintering trolley is the core component of the sintering furnace of ore smelting equipment. It is mainly used to sinter powder ore into blocks for use in the next blast furnace. The sintering trolley has a harsh working environment and high performance requirements. It needs to serve for a long time under cyclic thermal shock conditions and not leak. Similarly, the wind wheel roller, as a typical load transfer structure, is very prone to wear and cracking when bearing large loads. It is necessary to restore the shape and function of the structure through repair technology. Ductile iron is the main material of sintering trolleys and wind wheel rollers. It has excellent strength, toughness, high temperature resistance and good casting properties. However, after long-term service, the ductile iron structure of the sintering trolley and wind wheel roller is prone to defects such as wear, cracks and thermal corrosion pits, resulting in equipment failure. Direct replacement will greatly increase the cost. Repairing defective parts with welding repair methods can significantly reduce their operating costs and extend the service life of the equipment.

[0003] However, ductile iron has a high carbon content, poor plasticity, and poor uniformity of structure, which makes it poor in weldability. Welding ductile iron is a recognized problem in the industry. Repair is often more difficult than welding. In addition, the position of the repair area is uncertain and random, and the shape of the repair area is often a closed area. The repair stress is large, which can easily lead to repair failure. At present, in the welding and repair of ductile iron structures, the existing technology often adopts cast iron welding rods with a high Ni content, through beveling, multi-layer and multi-pass surfacing repair, and accurately controls the interlayer temperature, the length of each weld, and the welding current to prevent cracking and other problems during welding. However, the welding wire used is costly, the welding process is complicated, and the welding efficiency is low. Therefore, how to ensure high-efficiency, high-quality, and low-cost welding repairs of sintering trolleys and wind wheel rollers has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] At least in view of the technical problems mentioned in the background technology, the purpose of the present invention is to provide a welding wire for welding and repairing ductile iron structures of sintering trolleys and wind wheel rollers and a method for using the same.

[0005] The present invention adopts the following technical solution.

[0006] A welding wire for welding and repairing ductile iron structures of sintering trolleys and wind wheel rollers comprises the following components in percentage by mass: C: 0.03-0.07%, Cr: 10-12%, Mn: 8-10%, Si: 0.2-0.4%, Ni: 32-36%, Nb: 0.6-0.8%, and the balance comprises Fe and unavoidable impurities.

[0007] Furthermore, it also includes components Ga: 0.02-0.05%, In: 0.01-0.03%, RE<0.08%.

[0008] Preferably, the welding wire is composed of the following components in mass percentage: C: 0.05%, Cr: 11%, Mn: 9%, Si: 0.3%, Ni: 34%, Nb: 0.7%, Ga 0.03%, In 0.02%, RE 0.06%, and the balance is Fe and inevitable impurities.

[0009] In the present invention, the weld obtained after welding with the welding wire mainly contains Ni-Fe and Ni-Nb solid solutions, NbC compounds and M23C6 compounds.

[0010] In the present invention, the welding wire has a coating layer and a powder filling layer, the coating layer is made of a 304 stainless steel thin strip with a wall thickness of 0.4 mm and a width of 12 mm, and the powder filling layer is made of a mixture of high-purity electrolytic Mn powder, pure electrolytic Ni powder, Nb-Fe powder, Ga-Fe powder, Mn-In powder and Y2O3 powder, and the powder filling rate is 35-40%.

[0011] A method for using the aforementioned welding wire comprises the following steps: Step 1, mechanically grinding and cleaning the surface oxide layer of the defective parts of the sintering trolley structure or the wind wheel roller structure until the metallic luster is exposed to obtain the area to be repaired; Step 2, placing the welding wire in place, and welding the obtained area to be repaired by MIG welding method to obtain a weld; wherein the welding process parameters are: current 183-203A, voltage 18.7-20.3V, 99.9% pure Ar gas protection, welding speed 7-9mm / s, wire feeding speed 8.7-10.4mm / s; Step 3, mechanically process the obtained weld, and then directly install and use the sintering trolley structure or the wind wheel roller structure.

[0012] Preferably, the sintering trolley structure and the wind wheel roller structure are made of ductile iron, which is composed of the following components in mass percentage: C: 3.5-3.8%, Si: 2.2-2.7%, Mn < 0.5%, P < 0.07%, S < 0.02%, Mg: 0.03-0.06%, and the remainder is Fe and unavoidable impurities.

[0013] Beneficial effect: The weld obtained by using the welding wire of the present invention contains only Ni-Fe and Ni-Nb solid solutions, NbC compounds and M 23 The C6 compound does not contain any redundant brittle phases and has good crack resistance and mechanical properties. The area repaired by the scheme of the present invention is well formed, and does not have welding defects such as cracks and inclusions, so that the repaired parts can be used for a long time. By adopting the scheme of the present invention, the welding process does not require preheating, the temperature between the welding layers does not need to be controlled during the welding process, and annealing treatment is not required after the repair is completed. The parts can be directly installed and applied after mechanical processing, thereby realizing high-efficiency, high-quality, and low-cost welding repair of the sintering trolley and the wind wheel roller. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is the equilibrium solidification phase precipitation diagram of the welding wire in Example 1; Figure 2 The figure is a diagram of the wind wheel roller structure of the welding wire before and after repair in Example 2; Figure 3 is the mechanical property of the repaired area perpendicular to the surfacing direction in Example 3; Figure 4 It is the mechanical property of the repaired area parallel to the surfacing direction in Example 3. DETAILED DESCRIPTION

[0015] The technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] Embodiment 1: A welding wire, which is composed of the following components in mass percentage: C: 0.05%, Cr: 11%, Mn: 9%, Si: 0.3%, Ni: 34%, Nb: 0.7%, Ga 0.03%, In 0.02%, RE 0.06%, and the balance is Fe and inevitable impurities. In this embodiment: the welding wire has a coating layer and a powder filling layer, and the coating layer is made of a 304 stainless steel thin strip with a wall thickness of 0.4 mm and a width of 12 mm; when preparing the welding wire: the powder filling layer uses a mixture of high-purity electrolytic Mn powder (accounting for 22.33% of the total weight of the powder filling layer), pure electrolytic Ni powder (accounting for 75.26% of the total weight of the powder filling layer), Nb-Fe powder (accounting for 1.87% of the total weight of the powder filling layer), Ga-Fe powder (accounting for 0.08% of the total weight of the powder filling layer), Mn-In powder (accounting for 0.05% of the total weight of the powder filling layer) and Y2O3 powder (accounting for 0.16% of the total weight of the powder filling layer), and the powder filling rate is 37.5%.

[0017] The equilibrium solidification phase precipitation diagram of the welding wire in this embodiment is as follows: Figure 1 As shown in the figure, the equilibrium solidification structure of the welding wire is mainly Ni-Fe and Ni-Nb solid solutions, NbC compounds and M 23 C6 compound, there is no extra brittle phase, indicating that the weld obtained after welding with this welding wire has good crack resistance and good mechanical properties. Embodiment 2: Using the welding wire in Embodiment 1 to weld the defective part of the wind wheel roller structure (such as Figure 2 The wind wheel roller structure is made of ductile iron, which is composed of the following components by mass percentage (C: 3.6%, Si: 2.5%, Mn < 0.5%, P < 0.07%, S < 0.02%, Mg: 0.05%, the balance is Fe and unavoidable impurities), and the steps are as follows: Step 1, mechanically grinding the defective part of the wind wheel roller structure and cleaning the surface oxide layer until the metallic luster is exposed to obtain the area to be repaired; Step 2, placing the welding wire in place, and welding the obtained area to be repaired by MIG welding method to obtain a weld; wherein the welding process parameters are: current 201A, voltage 20 V, 99.9% pure Ar gas protection, welding speed 8mm / s, wire feeding speed 9.5mm / s; Step 3: Mechanically process the weld (e.g. Figure 2 As shown), the wind wheel roller structure can be directly installed and used.

[0018] Example 3: The welding wire in Example 1 is used to repair the defective parts of the sintering trolley wall plate structure. The material of the sintering trolley wall plate structure is ductile iron, which is composed of the following components in mass percentage (C: 3.8%, Si: 2.3%, Mn < 0.5%, P < 0.07%, S < 0.02%, Mg: 0.04%, and the balance is Fe and unavoidable impurities). The steps are as follows: Step 1, mechanically grinding the defective parts of the sintering trolley wall plate structure and cleaning the surface oxide layer until the metallic luster is exposed to obtain the area to be repaired; Step 2, placing the welding wire in place, and welding the obtained area to be repaired by MIG welding method to obtain a weld; wherein the welding process parameters are: current 203A, voltage 19.5V, 99.9% pure Ar gas protection, welding speed 8.5mm / s, wire feeding speed 10mm / s; Step 3: Mechanically process (grind and smoothen) the obtained weld, and then directly install and use the sintering trolley wall structure.

[0019] Comparative Example: Commercially available American-made ASM dissimilar steel welding rod (currently there is no welding wire on the market that meets the corresponding requirements of ductile iron welding, so only welding rod can be used), C accounts for 0.38%, Mn accounts for 11.4%, Si accounts for 0.14%, Ni accounts for 43.9%, Nb accounts for 0.7%, Cu accounts for 0.09, Cr accounts for 6.6%, P accounts for 0.004%, S accounts for 0.004, and the balance is Fe.

[0020] In the past, the ore smelting workshop of a certain enterprise used imported welding rods (i.e., the welding rods in the comparative example) to repair the sintering trolley wall panel structure, and the average service life after repair was about 12.5 months. After the sintering trolley wall panel structure was repaired using the solution in Example 3 (for the defective area, the pit area and depth were processed to the same size), the service life after repair has exceeded 13 months. The wind wheel roller structure in Example 2 cannot be repaired at present, because the only ASM heterogeneous steel welding rods available on the market are American-made ASM welding rods, and the use of such welding rods will directly cause the wind wheel roller to deform and become scrapped; while the solution in Example 2 is used to achieve the repair and reuse of the wind wheel roller, and the service life has exceeded 5 months.

[0021] RT testing and penetration testing were performed on the repaired areas in Example 2 and Example 3. The results showed that the repaired areas were free of defects such as cracks, slag inclusions, pores, and unfused areas, and met the use requirements.

[0022] The mechanical properties of the repaired area in Example 3 were tested, and the results are shown in Figure 3 and Figure 4As shown in the figure, it can be seen that the average tensile strength obtained in both directions reached 450MPa, which is about 90% of the strength of the parent material (ductile iron), meeting the performance requirements of the ductile iron structure after repair.

[0023] In the present invention, a welding wire with a specific proportion of components and structure is adopted, and its cost is significantly reduced compared with commercially available welding rods with basically the same performance (i.e., benchmarked against American dissimilar steel welding rods, C accounts for 0.38%, Mn accounts for 11.4%, Si accounts for 0.14%, Ni accounts for 43.9%, Nb accounts for 0.7%, Cu accounts for 0.09, Cr accounts for 6.6%, P accounts for 0.004%, S accounts for 0.004, and the balance is Fe). Not only the strength, wear resistance and temperature resistance of the welding wire are guaranteed, but also cracking can be prevented during welding, thereby realizing the domestic substitution of ink cast iron welding materials.

[0024] The weld obtained by the welding wire of the embodiment basically contains only Ni-Fe and Ni-Nb solid solutions, NbC compounds and M23C6 compounds, and there is no unnecessary brittle phase or the like, and the weld has good crack resistance and mechanical properties; the area repaired by the embodiment scheme is well formed, and there are no welding defects such as cracks and inclusions, so the repaired parts can be used for a long time, and no preheating is required during the welding process, and no temperature control is required between the welding layers during the welding process. After the repair is completed, no annealing treatment is required, and the weld can be directly installed and applied after mechanical processing, thereby realizing high-efficiency, high-quality and low-cost welding repair of the sintering trolley and the wind wheel roller.

Claims

1. A welding wire for welding and repairing ductile iron structures of sintering trolleys and wind wheel rollers, comprising the following components by mass percentage: C: 0.03-0.07%, Cr: 10-12%, Mn: 8-10%, Si: 0.2-0.4%, Ni: 32-36%, Nb: 0.6-0.8%, and the balance includes Fe and unavoidable impurities.

2. The welding wire according to claim 1, characterized in that It also includes components Ga: 0.02-0.05%, In: 0.01-0.03%, and RE<0.08%.

3. The welding wire according to claim 1 or 2, characterized in that: C: 0.05%, Cr: 11%, Mn: 9%, Si: 0.3%, Ni: 34%, Nb: 0.7%, Ga 0.03%, In 0.02%, RE 0.06%.

4. The welding wire according to claim 1, characterized in that: The weld obtained by welding with the welding wire mainly contains Ni-Fe and Ni-Nb solid solutions, NbC compounds and M23C6 compounds.

5. The welding wire according to any one of claims 1 to 4, characterized in that: The welding wire comprises a coating layer and a powder filling layer, wherein the coating layer is made of a 304 stainless steel thin strip with a wall thickness of 0.4 mm and a width of 12 mm, and the powder filling layer is made of a mixture of high-purity electrolytic Mn powder, pure electrolytic Ni powder, Nb-Fe powder, Ga-Fe powder, Mn-In powder and Y2O3 powder, and the powder filling rate is 35-40%.

6. A method for using the welding wire according to any one of claims 1 to 5, characterized in that the steps include: Step 1, mechanically grinding and cleaning the surface oxide layer of the defective parts of the sintering trolley structure or the wind wheel roller structure until the metallic luster is exposed to obtain the area to be repaired; Step 2, placing the welding wire in place, and welding the obtained area to be repaired by MIG welding method to obtain a weld; wherein the welding process parameters are: current 183-203A, voltage 18.7-20.3V, 99.9% pure Ar gas protection, welding speed 7-9mm / s, wire feeding speed 8.7-10.4mm / s; Step 3, mechanically process the obtained weld, and then directly install and use the sintering trolley structure or the wind wheel roller structure.

7. The method for using the welding wire according to claim 6, characterized in that: The material of the sintering trolley structure and the wind wheel roller structure is ductile iron, which is composed of the following components in mass percentage: C: 3.5-3.8%, Si: 2.2-2.7%, Mn < 0.5%, P < 0.07%, S < 0.02%, Mg: 0.03-0.06%, RE < 0.06%.

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