Side guide member

Abstract

To provide a side guide member that includes a spray coating layer having excellent wear resistance, seizure resistance, adhesion property and impact resistance on a substrate surface.SOLUTION: A side guide member includes a Ni-based self-fluxing alloy thermal spray coating including 20-40 wt.% of WC, 3-5 wt.% of Co, 0-5 wt.% of Cr and the balance being Ni-based self-fluxing alloy with inevitable impurities, on a substrate surface.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a side guide member for a hot rolling mill. [Background technology]

[0002] Side guide members for hot rolling equipment, such as side guide liners or hard side guide rolls, are components that prevent steel sheets from flying out of the conveying line by controlling the stripping of steel sheets conveyed at high temperatures of 500°C to 900°C by rolling rolls or the like within the width direction of the conveying line. Side guide members are used in extremely harsh environments where they are subjected to sliding and temperature rise due to contact with the steel sheets, and therefore are required to have excellent wear resistance, seizure resistance, adhesion, and cracking resistance.

[0003] Conventionally, various techniques have been used for side guide members to solve the above-mentioned problems. For example, Patent Documents 1 to 4 disclose inventions in which side guide members are subjected to CrC-Co-based alloy overlay welding, CrC-Ni-based alloy overlay welding, NbC-Co-based alloy overlay welding, and high-speed steel NbC overlay welding. In addition to overlay welding, Patent Documents 5 to 7 disclose inventions in which side guide members are subjected to Ni-Cr alloy thermal spraying, WC thermal spraying, WC-Co thermal spraying, and NbC-NiCr thermal spraying. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 63-260619 [Patent Document 2] Special Publication No. 03-059768 [Patent Document 3] Special Publication No. 08-009115 [Patent Document 4] Japanese Patent Application Laid-Open No. 2018-176195 [Patent Document 5] Japanese Patent Application Publication No. 63-309304 [Patent Document 6] Japanese Patent Application Publication No. 05-169114 [Patent Document 7] Japanese Patent Application Laid-Open No. 2000-282216 Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, side guide members are used in extremely harsh environments, which causes severe wear and deterioration of the coating, and therefore the coating must be reapplied frequently.In recent years, there has been a demand for coatings that can reduce the frequency of reapplication in order to reduce environmental impact and costs.

[0006] However, as described in Patent Documents 1 to 4, when CrC-Co-based alloy overlay welding, CrC-Ni-based alloy overlay welding, NbC-Co-based alloy overlay welding, etc. are applied to the side guide member, thermal distortion may occur in the base material.

[0007] Furthermore, when a coating is formed on a side guide member by Ni-Cr alloy spraying, WC spraying, WC-Co spraying, or NbC-NiCr spraying, as in the inventions described in Patent Documents 5 to 7, the wear resistance, adhesion, and cracking resistance are insufficient, and there is a risk of the coating peeling off, so it has been necessary to frequently reapply the build-up.

[0008] Under these circumstances, an object of the present invention is to provide a side guide member having a thermal sprayed layer on the surface of a substrate, the thermal sprayed layer having excellent abrasion resistance, seizure resistance, adhesion, and impact resistance. [Means for solving the problem]

[0009] (1) A side guide member according to one embodiment of the present invention is provided on a substrate surface with a Ni-based self-fluxing alloy sprayed coating containing 20 to 40 weight percent WC, 3 to 5 weight percent Co, 0 to 5 weight percent Cr, and the remainder being a Ni-based self-fluxing alloy and unavoidable impurities.

[0010] (2) The Ni-based self-fluxing alloy preferably contains 2 to 5 wt % Si, 2 to 4 wt % B, and the balance Ni. [Effects of the Invention]

[0011] The present invention provides a side guide member that can reduce the frequency of reapplication of the coating by providing a Ni-based self-fluxing alloy spray coating on the substrate surface, which has excellent wear resistance, seizure resistance, adhesion, and impact resistance. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention is applicable to side guide members used in hot rolling equipment, such as side guide liners and side guide hard rolls.

[0013] The side guide member of this embodiment is provided on the substrate surface with a Ni-based self-fluxing alloy sprayed coating containing 20 to 40 weight percent WC, 3 to 5 weight percent Co, 0 to 5 weight percent Cr, and the remainder being a Ni-based self-fluxing alloy and unavoidable impurities.

[0014] WC is an element that improves wear resistance, but if the amount added exceeds 40 wt%, toughness and thermal shock resistance decrease. On the other hand, if the amount added is less than 20 wt%, the effect of wear resistance cannot be fully obtained. Therefore, the amount of WC added is set to 20 to 40 wt%.

[0015] Co is an element that acts as a binder to bind WC particles together, but if the amount added exceeds 5 wt%, the bonding between WC particles becomes insufficient, causing the thermal spray coating to become embrittled. On the other hand, if the amount added is less than 3 wt%, the Vickers hardness of the coating surface of the thermal spray coating decreases, resulting in reduced wear resistance. Therefore, the amount of Co added was set to 3 to 5 wt%.

[0016] Cr is an element that improves oxidation resistance, but if the amount added exceeds 5 wt%, a hard and brittle Cr carbide layer or Cr boride layer will form at the boundary between the substrate and the thermal spray coating during fusing, reducing the adhesion of the thermal spray coating. Therefore, the amount of Cr added is set to 0 to 5 wt%.

[0017] In this way, the side guide member of this embodiment has a Ni-based self-fluxing alloy spray coating on the substrate surface, which contains 20 to 40 weight percent WC, 3 to 5 weight percent Co, 0 to 5 weight percent Cr, and the remainder is made of a Ni-based self-fluxing alloy and unavoidable impurities, thereby providing the side guide member with excellent wear resistance, seizure resistance, adhesion, and impact resistance.

[0018] The Ni-based self-fluxing alloy contained in the Ni-based self-fluxing alloy thermal spray coating of this embodiment preferably contains 2 to 5 wt % Si, 2 to 4 wt % B, and the balance Ni.

[0019] Silicon acts as a deoxidizer during the fusing process, reducing oxides and pores in the thermal spray coating, improving impact resistance, and imparting self-fluxing properties to the alloy powder. However, if the amount added exceeds 5% by weight, the alloy becomes too hard and brittle, making it more susceptible to cracking. On the other hand, if the amount added is less than 2% by weight, it becomes difficult to obtain a sufficient fusing effect. Therefore, the amount of silicon added is preferably 2 to 5% by weight.

[0020] Like Si, B improves impact resistance and also imparts self-fluxing properties to the alloy powder. However, if the amount added exceeds 4 wt%, the alloy becomes too hard and brittle, making it more susceptible to cracking. On the other hand, if the amount added is less than 2 wt%, it becomes difficult to obtain a sufficient fusing effect. Therefore, the amount of B added is preferably 2 to 4 wt%.

[0021] As described above, the Ni-based self-fluxing alloy contained in the Ni-based self-fluxing alloy spray coating of this embodiment contains 2 to 5 weight percent Si, 2 to 4 weight percent B, and the remainder Ni, which imparts self-fluxing properties to the alloy powder and also makes it possible to improve wear resistance and impact resistance.

[0022] Next, a method for manufacturing the side guide member according to this embodiment will be described.

[0023] First, a powder containing 20-40 wt% WC, 3-5 wt% Co, 0-5 wt% Cr, and the balance being a Ni-based self-fluxing alloy and unavoidable impurities is sprayed onto the substrate surface of the side guide member. The Ni-based self-fluxing alloy contains 2-5 wt% Si, 2-4 wt% B, and the balance being Ni.

[0024] Examples of thermal spraying methods that can be applied in this embodiment include plasma spraying and flame spraying, among which atmospheric plasma spraying is preferred.

[0025] Next, the Ni-based self-fluxing alloy thermal spray coating is subjected to a fusing treatment (remelting treatment). The fusing treatment reduces the pores in the thermal spray coating, making it denser, and also forms a diffusion layer between the substrate and the thermal spray coating, resulting in a thermal spray coating with high adhesion. The fusing treatment is preferably a heat treatment involving remelting in air or a non-oxidizing atmosphere at a temperature of 1000 to 1100°C for 30 to 240 minutes. [Example]

[0026] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0027] Example 1 A self-fluxing alloy powder containing 33 wt% WC, 4 wt% Co, and 0 wt% Cr, with the remainder consisting of a Ni-based self-fluxing alloy and unavoidable impurities, was prepared. The Ni-based self-fluxing alloy contained 3 wt% Si and 2 wt% B, with the remainder consisting of Ni. A 50 mm x 50 mm x 10 mm thick S45C substrate was then subjected to atmospheric plasma spraying under the following conditions to form a thermal spray coating. Current value: 400A Argon gas flow rate: 36NLPM Thereafter, a fusing treatment was carried out under the conditions described in paragraph 0025 to prepare a test piece of Example 1.

[0028] (Comparative Example 1) A self-fluxing alloy powder containing 4 wt% Si, 3 wt% B, and the remainder Ni was prepared. Then, flame spraying was performed on a 50 mm x 50 mm x 10 mm S45C substrate under the following conditions to form a thermal spray coating. A fusing process was then performed under the conditions described in paragraph 0025 to produce a test piece for Comparative Example 1. Acetylene flow rate: 14.5 NLPM Oxygen flow rate: 26NLPM

[0029] (Comparative Example 2) A thermal spray powder containing 10 wt% Co, 4 wt% Cr, and the remainder WC was prepared. A 50 mm × 50 mm × 10 mm thick S45C substrate was then subjected to high-velocity flame spraying under the following conditions to form a thermal spray coating, producing a test piece for Comparative Example 2. Oxygen flow rate: 1900SCFH Kerosene flow rate: 6 GPH

[0030] (Comparative Example 3) A thermal spray powder containing 50 wt% Ni and 50 wt% Cr was prepared. Then, flame spraying was performed on a 50 mm × 50 mm × 10 mm S45C substrate under the same conditions as in Comparative Example 1 to form a thermal spray coating, and a test piece for Comparative Example 3 was produced.

[0031] The various tests and test conditions used to evaluate the Examples and Comparative Examples will be described below.

[0032] (Wear resistance test) In the abrasion resistance test, the abrasion loss was measured using a Suga abrasion test under the following test conditions: Load: 3.25 kg·f Number of round trips: 2000 Test paper: SiC#320

[0033] (Film hardness test) The coating hardness was measured using a micro Vickers hardness tester under the following test conditions: Load: 300gf

[0034] (Adhesion test) In the adhesion test, the adhesive strength was measured by a shear test under the following test conditions: Testing machine: AG-Xplus (Shimadzu Corporation) Test speed: 1mm / min Test temperature: Room temperature (25°C)

[0035] (Crack resistance test) In the crack resistance test, a steel ball indentation test was carried out under the following test conditions: Load: 10kN Steel ball: SUJ2 φ20mm

[0036] (Seizure resistance test) In the seizure resistance test, a pin-on-disk test was carried out under the following test conditions: Counterpart material: SS400 Load: 5N Turning radius: 6mm Friction speed: 16.67cm / s Friction distance: 400m

[0037] The results of various tests in Example 1 and Comparative Examples 1 to 3 are shown in Table 1 below. The criteria for ◎, 〇, △, and × in Table 1 are as follows: (wear resistance) ◎: Abrasion loss less than 20 mg 〇: Abrasion loss is 20 mg or more and less than 70 mg △: Abrasion loss is 70 mg or more and less than 120 mg ×: Abrasion loss is 120 mg or more (adhesion) ◎: Adhesion strength is 350 MPa or more 〇: Adhesion strength is 300MPa or more and less than 350MPa △: Adhesion strength is 250 MPa or more and less than 300 MPa ×: Adhesion strength is less than 250 MPa (crack resistance) ◎: The diameter of the indentation when the steel ball is pressed in is less than 1.8 mm 〇: The diameter of the indentation when the steel ball is pressed is 1.8 mm or more and less than 2.1 mm △: The diameter of the indentation when the steel ball is pressed is 2.1 mm or more and less than 2.4 mm ×: The diameter of the indentation when the steel ball is pressed in is 2.4 mm or more (Seizure resistance) ◎: The area of ​​the friction mark on the mating material is 0.2 mm 2 less than 〇: The area of ​​the friction mark on the mating material is 0.2 mm 2 Over 1.0mm 2 less than △: The area of ​​the friction mark on the mating material is 1.0 mm 2 Over 5.0mm 2 less than ×: The area of ​​the friction mark on the mating material is 5.0 mm 2 End

[0038] [Table 1]

[0039] The results in Table 1 confirm that the Ni-based self-fluxing alloy spray coating (Example 1) formed under conditions compatible with the present invention exhibits excellent properties in terms of wear resistance, seizure resistance, adhesion, and impact resistance.

Claims

[Claim 1] A side guide member provided on a substrate surface with a Ni-based self-fluxing alloy sprayed coating containing 20 to 40 wt % WC, 3 to 5 wt % Co, 0 to 5 wt % Cr, 1 to 3.85 wt % Si, 1 to 3.08 wt % B, with the balance being Ni and unavoidable impurities.

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