CN-121972905-A - Repairing method for cobalt-base alloy blade of steel billet hydraulic shear

CN121972905ACN 121972905 ACN121972905 ACN 121972905ACN-121972905-A

Abstract

The invention relates to the technical field of ferrous metallurgy equipment maintenance and welding repair and discloses a steel billet hydraulic shear cobalt-base alloy blade repairing method which comprises the steps of S1 pretreatment, low-pressure sand blasting cleaning, removal of a failure layer, grinding and removal of a carburized layer with the wall of 0.05-0.2mm, S2 selection of a Co-Cr-W-C cobalt-base welding wire with a certain proportion, S3 overlaying, preheating a blade to 280-320 ℃ and strictly controlling the temperature of a blade holder to be not more than 180 ℃, multilayer multi-pass overlaying by adopting a TIG (tungsten inert gas) welding machine, 560-600 ℃ stress relief annealing after welding, S4 machining, and grinding and recovering geometric dimensions. According to the invention, through removing the carburized layer, gradient temperature control and special heat treatment system, the problems that cracks and pores are easy to generate in cobalt-based alloy welding and the tool apron base body is overheated, softened and deformed are effectively solved, the metallurgical bonding strength, high-temperature wear resistance and thermal fatigue resistance life of the repaired cutting edge are improved, and the service period of equipment is prolonged to a great extent.

Inventors

ZHANG XIN
FENG XIAOJIE
WU WEIPING
TIAN XUEFENG
YANG TAO
ZHANG SHENNING

Assignees

广东松山职业技术学院

Dates

Publication Date: 20260505
Application Date: 20251211

Claims (10)

1. A repairing method of a cobalt-based alloy blade of a steel billet hydraulic shear is characterized by comprising the following steps: S1, a pretreatment stage, namely adopting low-pressure sand blasting with the pressure of 0.4-0.6MPa to remove oxide skin and adhered steel scraps on the surface of a blade, then removing a failure layer material at the original blade position, and removing the failure layer material to a depth of 2.0-3.0mm until a matrix is exposed; S2, a welding material determining stage, namely selecting a cobalt-based welding wire with the diameter of 2.0-3.2mm as a filling material, wherein the chemical components of the cobalt-based welding wire comprise Co, cr, W and C; S3, an autonomous surfacing stage, namely preheating the blade to 280-320 ℃ and preserving heat for 20-40min, controlling the temperature of the tool apron to be not more than 180 ℃, adopting a TIG welder to carry out multilayer multi-pass surfacing, controlling the interlayer temperature to be 250-280 ℃ in the welding process, slowly cooling to 280-320 ℃ after the welding is finished, carrying out heat treatment after preserving heat for 1.5-3.0h at 560-600 ℃ immediately, and finally cooling along with a furnace; and S4, in the machining and performance verification stage, the inner hole of the tool apron is used as a positioning reference, the repaired cutting edge is subjected to rough grinding and fine grinding, and the geometric dimension of the cutting edge is recovered.
2. The method for repairing the cobalt-based alloy cutting edge of the steel billet hydraulic shear according to claim 1 is characterized in that in the step S1, white corundum with 100-140 meshes is selected as sand material for low-pressure sand blasting, and the concrete operation of removing the carburized layer is that an angle grinder with a 200-280-mesh grinding wheel is used for grinding the planed groove wall.
3. The method for repairing the cobalt-based alloy blade of the steel billet hydraulic shear according to claim 1, wherein in the step S2, the mass fraction of chemical components of the cobalt-based welding wire is 27.0% -30.0% of Cr, 4.0% -5.0% of W, 0.88% -0.92% of C and the balance Co and unavoidable impurities.
4. The repairing method for the cobalt-based alloy cutting edge of the steel billet hydraulic shear according to claim 1, wherein in the step S3, the preheating is specifically realized in such a way that an electric heating plate with the power of 400-600W is attached to a non-welding area of the cutting edge, and heating is controlled by an intelligent temperature controller, so that the temperature difference of the heating area is less than or equal to 15 ℃.
5. The method for repairing the cobalt-based alloy cutting edge of the steel billet hydraulic shear according to claim 1, wherein in the step S3, welding parameters of the TIG welding machine are set to be 120-130A of welding current, 18-19V of welding voltage, 90-100mm/min of welding speed and 10-15L/min of argon protection flow.
6. The method for repairing the cobalt-based alloy cutting edge of the steel billet hydraulic shear according to claim 1, wherein in the step S3, the specific requirement of the multilayer multi-pass build-up welding is that the thickness of a single pass weld is less than or equal to 2.5mm, and the temperature between layers is monitored and controlled after 3-8min of each pass of welding.
7. The method for repairing the cobalt-based alloy cutting edge of the steel billet hydraulic shear according to claim 1, wherein in the step S3, the treatment step after the welding is finished is specifically that the cutting edge is immediately wrapped by ceramic fiber cloth for slow cooling, then the ceramic fiber cloth is put into a box-type resistance furnace, the temperature is raised through the temperature raising rate of 3-8 ℃ per minute, and the steel billet hydraulic shear is discharged from the furnace after the heat preservation is finished and is cooled to below 200 ℃.
8. The method for repairing the cobalt-based alloy cutting edge of the steel billet hydraulic shear according to claim 1, wherein in the step S4, a 60-100 mesh diamond grinding wheel is adopted for rough grinding, the grinding amount is 1.0-2.0mm, a 180-240 mesh diamond grinding wheel is adopted for fine grinding, and the cutting edge angle is restored to 28-32 degrees.
9. The method for repairing the cobalt-based alloy cutting edge of the steel billet hydraulic shear according to claim 1, wherein after the step S4 is completed, the method further comprises a performance verification step of detecting and ensuring that the interference of the joint surface of the tool apron is 0.05-0.12mm and the shearing clearance is controlled to be 0.2-0.3mm.
10. The repairing method for the cobalt-based alloy blade of the steel billet hydraulic shear according to claim 1, wherein in the step S3, the operation details of the overlaying welding further comprise the steps of adopting a segmented welding method, wherein each segment is 300-500mm in length, selecting a cerium tungsten electrode with the diameter of 3.0-4.0mm during welding, controlling the distance between the tip of the tungsten electrode and a welding line to be 3-5mm, keeping the included angle between a welding gun and the welding line to be 10-20 degrees, and cleaning welding slag by using dry compressed air with the pressure of 0.4-0.6MPa after one layer is welded.

Description

Repairing method for cobalt-base alloy blade of steel billet hydraulic shear Technical Field The invention relates to the technical field of ferrous metallurgy equipment maintenance and welding repair, in particular to a method for repairing a cobalt-base alloy blade of a steel billet hydraulic shear. Background At present, in the continuous casting and rolling process of the ferrous metallurgy industry, the steel billet hydraulic shear plays a key role, and the cutting edge of a core execution part of the steel billet hydraulic shear needs to work under the high-temperature radiation of 1150-1250 ℃ for a long time and frequently bears the severe extrusion friction and the instantaneous impact load of the red hot steel billet. In order to cope with severe working conditions, the blade substrate is usually made of UMCo cobalt-based heat-resistant alloy, and the material is the first choice for guaranteeing the billet notch quality and the sizing precision by virtue of excellent high-temperature red hardness and chemical stability. However, under the continuous action of the ultimate heat strength, the cutting edge inevitably undergoes wear thinning, thermal fatigue cracking or partial chipping, resulting in failure of the shearing function. For such failed blades, the industry has generally tended to employ welding remanufacturing techniques to repair the blade in place of the costly overall scrapping replacement. Conventional repair logic typically involves removal of the surface failure layer, selection of homogenous or heterogeneous alloy weldments for weld overlay filling, and final restoration of geometry via machining. As a resource regeneration means for reducing the purchasing cost of spare parts and maintaining the continuous operation of a production line, welding repair can theoretically prolong the service cycle of the blade and relieve the stock pressure of the spare parts to a certain extent. However, the existing repair technology is limited by the complexity of dissimilar material welding, and the repair quality is often unstable due to the lack of process details. Because the microscopic carburized layer formed on the surface of the groove wall after long-term high-temperature service of the cutting edge is ignored, the carbon-rich region is easy to induce interfacial pores and brittle martensitic structure during direct welding, so that the bonding strength of the weld line is insufficient, and the repair layer is easy to peel. The partial process is to inhibit cold cracks of the cobalt-base alloy, and blindly implement integral high-temperature preheating, but not to thermally isolate the 42CrMo tool apron, and the heat conduction is easy to cause tempering softening or thermal deformation of the tool apron base body, so that the interference assembly precision is lost. In addition, if the ratio of the welding materials is mismatched with the postweld heat treatment system, residual tensile stress caused by low heat conduction and high expansion characteristics of the cobalt-based alloy cannot be effectively released, the repaired blade is easy to generate fatigue cracks again under cold-hot alternating impact, and the wear-resisting life is difficult to reach expectations. Therefore, the invention provides a method for repairing the cobalt-based alloy cutting edge of the steel billet hydraulic shear, which aims to solve the defects in the prior art. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a method for repairing the cobalt-based alloy cutting edge of the steel billet hydraulic shear, which solves the problems that welding cracks and interface defects are easy to generate in the repairing process of the cobalt-based alloy cutting edge of the traditional steel billet hydraulic shear, and the tool apron base body is softened and deformed due to overheating so as to lose the assembly precision. In order to achieve the purpose, the invention is realized by the following technical scheme that the method for repairing the cobalt-based alloy blade of the steel billet hydraulic shear comprises the following steps: S1, a pretreatment stage, namely adopting low-pressure sand blasting with the pressure of 0.4-0.6MPa to remove oxide skin and adhered steel scraps on the surface of a blade, then removing a failure layer material at the original blade position, and removing the failure layer material to a depth of 2.0-3.0mm until a matrix is exposed; S2, a welding material determining stage, namely selecting a cobalt-based welding wire with the diameter of 2.0-3.2mm as a filling material, wherein the chemical components of the cobalt-based welding wire comprise Co, cr, W and C; S3, an autonomous surfacing stage, namely preheating the blade to 280-320 ℃ and preserving heat for 20-40min, controlling the temperature of the tool apron to be not more than 180 ℃, adopting a TIG welder to carry out multilayer multi-pass surfacing, controlling the interlayer temperat