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Method of enhancing surface hardness of ferrite nodular cast iron

A nodular cast iron, surface hardness technology, applied in the direction of welding medium, arc welding equipment, welding/cutting medium/material, etc., can solve the problems of high cost, unsuitable local surface strengthening, etc., and achieve stable quality, low cost, and process method simple effect

Inactive Publication Date: 2013-12-04
YANSHAN UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, the cost of the above method is high, and it is not suitable for large-sized castings and local surface strengthening of castings.

Method used

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  • Method of enhancing surface hardness of ferrite nodular cast iron

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0012] A low-carbon alloy electrode with a diameter of 4mm was prepared by a conventional method, and the chemical composition (mass fraction wt%) of the weld metal was: C0.12%, Mn0.42%, Cr0.50%, Ni1.20%, Si0.32 %, S0.027%, P0.032%, and the rest is Fe. After drying the electrode at 300°C for 1 hour, use a DC welding machine to surfacing the electrode on the surface of ferritic ductile iron with a current of 160A. The thickness of the overlay layer is 1.5mm. 1.5mm surfacing layer. Use a hardness tester and a microscope to test the surface hardness and hard layer thickness of the nodular cast iron after overlay welding. The hardness values ​​and hard layer thickness are shown in Table 1.

Embodiment 2

[0014] A low-carbon alloy electrode with a diameter of 4 mm was prepared by a conventional method, and the chemical composition (mass fraction wt%) of the welding layer metal was: C0.18%, Mn0.60%, Cr0.68%, Ni1.28%, Si0.31 %, S0.024%, P0.033%, and the rest is Fe. After drying the electrode at 400°C for 1 hour, use a DC welding machine to surfacing the electrode on the surface of ferritic ductile iron with a current of 170A. The thickness of the overlay layer is 2.0mm. 2.0mm surfacing layer. Use a hardness tester and a microscope to test the surface hardness and hard layer thickness of the nodular cast iron after overlay welding. The hardness values ​​and hard layer thickness are shown in Table 1.

Embodiment 3

[0016] A low-carbon alloy electrode with a diameter of 4mm was prepared by a conventional method, and the chemical composition (mass fraction wt%) of the weld metal was: C0.20%, Mn0.30%, Cr0.80%, Ni1.30%, Si0.30 %, S0.025%, P0.031%, and the rest is Fe. After drying the electrode at 350°C for 1 hour, use a DC welding machine to surfacing the electrode on the surface of ferritic nodular cast iron with a current of 220A. The thickness of the surfacing layer is 1.0mm. 1.0mm surfacing layer. Use a hardness tester and a microscope to test the surface hardness and hard layer thickness of the nodular cast iron after overlay welding. The hardness values ​​and hard layer thickness are shown in Table 1.

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Abstract

Provided is a method of enhancing surface hardness of ferrite nodular cast iron. The method mainly comprises the steps that a low-carbon alloy welding rod with the diameter being 4mm is made in a conventional method, and a weld layer of the low-carbon alloy welding rod comprises, by mass, C 0.12%-0.20%, Mn 0.30-0.60%, Cr 0.50%-0.80%, Ni 1.20%-1.30%, Si <=0.4%, S <=0.030%, P <=0.035%, and the balance Fe. The welding rod is dried for 1h at the temperature ranging from 300 DEG C to 400 DEG C before being used, a built-up welding layer with the thickness ranging from 1mm to 2mm is formed on the surface of the nodular cast iron by the welding rod through a direct current welding machine by means of a 160-220A current in a built-up welding mode, the built-up welding layer is air-cooled to room temperature after welding, then the built-up welding layer with the thickness ranging from 1mm to 2mm on the surface of the nodular cast iron is grinded off, and a fusion layer of the surface of the nodular cast iron is obtained. The method achieves simple techniques, low cost, and quality stability, and the surface hardness of the nodular cast iron is 48-52 HRC and is increased by 360%-390% compared with that of the nodular cast iron before processing.

Description

technical field [0001] The invention belongs to the field of metal material science and technology, in particular to a preparation method of nodular cast iron. Background technique [0002] Ductile iron not only has excellent mechanical properties, simple production process, low cost and is not limited by the size of castings, but also maintains the characteristics of gray cast iron such as wear resistance, vibration reduction and notch insensitivity. In addition, ductile iron can be subjected to various heat treatments to further improve its structure and mechanical properties. Therefore, ductile iron has been widely used in agricultural machinery, mining machinery, petrochemical and other industries. However, the disadvantage of ductile iron is that the surface hardness is low, and it is easy to deform and wear during application. Usually, the way to improve the surface hardness of ductile iron is to perform surface strengthening treatments such as high-frequency quenchi...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B23K9/04B23K35/24C22C38/40
Inventor 张瑞军郑春雷闫志刚刘建华
Owner YANSHAN UNIV