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A method for treating the surface of gray cast iron with ultrafine nodular graphite

A treatment method, gray cast iron technology, applied in the field of gray cast iron surface ultra-fine ductile graphite treatment, can solve gray cast iron poor oxidation resistance and thermal fatigue resistance, alloy elements increase mold production costs, large interface stress of dissimilar metals and other problems, Achieve the effects of improving oxidation resistance and thermal fatigue resistance, environmental protection labor intensity, and high nucleation rate

Active Publication Date: 2018-07-03
NANJING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the oxidation resistance and thermal fatigue resistance of gray cast iron are poor, and the inner cavity of the mold is prone to thick oxide skin or thermal fatigue cracking during service, resulting in cracks
[0004] Most of the existing methods use thermal spraying of nickel-based self-fluxing alloy powder in the cavity of the mold or casting dissimilar metals to achieve compounding, which improves the performance of the mold to a certain extent, but the former sprayed layer is prone to fall off during use, and the latter It is easy to have disadvantages such as large stress at the interface of dissimilar metals and complicated process
In the literature ("Research on multi-alloyed D-type graphite cast iron glass mold" Master's thesis of Hefei University of Technology), when casting glass molds, adding appropriate amount of V, Ti and other alloying elements and chilling the inner cavity of the mold with cold iron can obtain D-type Graphite cast iron, but it is still flake graphite in essence, there is stress concentration at the end of graphite, and the addition of alloying elements and the use of chilled iron increase the cost of mold production

Method used

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  • A method for treating the surface of gray cast iron with ultrafine nodular graphite

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0022] The surface of the gray cast iron (the carbon content of the gray cast iron is 3.57wt% and the silicon content 2.00wt%) is smoothed with sandpaper, cleaned with alcohol and acetone, and then dried. Set laser power P=2000W, scan speed v=15mm / s, defocus z=18mm, carry out laser surface fusion treatment on gray cast iron, blow Ar gas protection sideways during treatment, and the gas output rate is 25L / min.

[0023] After the laser surface melting treatment, put the sample into a 950°C resistance furnace, keep it warm for 4 hours, and then cool it in the furnace. When the temperature drops below 400-500°C, take it out and cool it in air.

[0024] The main features and properties of the gray cast iron treated in Example 1 are shown in Table 1.

Embodiment 2

[0026] The surface of the gray cast iron (the carbon content of the gray cast iron is 3.52wt% and the silicon content 2.08wt%) is smoothed with sandpaper, cleaned with alcohol and acetone, and then dried. Set laser power P=1800W, scan speed v=18mm / s, defocus z=16mm, carry out laser surface fusion treatment on gray cast iron, blow Ar gas protection from the side during treatment, and the gas output rate is 25L / min.

[0027] After the laser surface melting treatment, put the sample into a 900°C resistance furnace, keep it warm for 4 hours, and then cool it in the furnace. When the temperature drops below 400-500°C, take it out and cool it in air.

[0028] The main characteristics and properties of the gray cast iron treated in Example 2 are shown in Table 1.

Embodiment 3

[0030] The surface of the gray cast iron (the carbon content of the gray cast iron is 3.48wt% and the silicon content 2.12wt%) is smoothed with sandpaper, cleaned with alcohol and acetone, and then dried. Set laser power P=2200W, scan speed v=14mm / s, defocus z=20mm, carry out laser surface fusion treatment on gray cast iron, side blow Ar gas protection during treatment, and gas output rate is 25L / min.

[0031] After the laser surface melting treatment, put the sample into an 850°C resistance furnace, keep it warm for 4 hours, and then cool it in the furnace. When the temperature drops below 400-500°C, take it out and cool it in air.

[0032] The main features and properties of the gray cast iron treated in Example 3 are shown in Table 1.

[0033] Table 1 The main characteristics and properties of gray cast iron surface after superfine nodular graphite treatment

[0034]

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Abstract

The invention discloses a gray pig iron surface ultrathin spheroidizing method. A gray pig iron comprises, 3.3 to 3.6% of C, 2.0 to 2.4% of Si, 0.5 to 0.8% of Mn, smaller than 0.1% of P, smaller than 0.1% of S and the balance Fe. The method comprises following treatment steps: the gray pig iron is subject to laser surface fusing treatment; the gray pig iron subject to laser surface fusing treatment is subject to spheroidizing annealing; the ultrathin spherulitic graphite layer with the millimeter-level thickness is obtained on the surface of the gray pig iron treated through the method, the average diameter of the spherulitic graphite is one micrometer or below, the density of the graphite precipitation face reaches 105 / mm<2>, and the main graphite of the finally-prepared gray pig iron material is kept unchangeable in form and size, and the property advantages are kept; the spherulitic graphite gray pig iron has the surface several-millimeter depth, the graphite size is small, distribution is uniform, and the surface layer has the excellent thermal fatigue resistance and oxidation resistance.

Description

technical field [0001] The invention belongs to the field of gray cast iron surface treatment, in particular to a method for treating the surface of gray cast iron with superfine nodular graphite. Background technique [0002] The glass mold is a tool for forming glass products, and its performance characteristics and surface quality of the inner cavity determine the molding quality of glass products to a large extent. The glass forming temperature is above 1100°C, which is higher than the glass liquidus line, and the inner cavity of the glass mold is frequently in contact with the high-temperature molten glass, which puts forward high requirements for its heat resistance. At the same time, in order to ensure a high production speed and production efficiency, the molten glass needs to quickly transfer heat through the mold when it is cooled, and the material is required to have excellent thermal conductivity. In addition, during the opening and closing process of the mold, ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C21D5/14C21D1/26
CPCC21D1/26C21D5/14
Inventor 吴兴超李永胜张鑫
Owner NANJING UNIV OF SCI & TECH