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Casting defect eliminating method

A technology for casting defects and defects, applied in the field of casting defect elimination, can solve problems such as cracking, and achieve the effect of improving welding repair quality, saving time and ensuring overall performance.

Inactive Publication Date: 2018-12-25
ANHUI MAGANG HEAVY MASCH MFG CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] Aiming at the problem that cracking is easy to occur when repairing defects of large steel castings in the prior art, the present invention provides a method for eliminating defects of castings

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0039] For the defects of large steel castings, it is difficult to repair them by conventional repair methods, and cracks are prone to appear in the repaired area. To solve this problem, the characteristics of steel castings and the mechanism of cracks are analyzed. Generally speaking, its structure is a thick and large cross-section structure. During production, the liquid metal solidifies for a long time after pouring, so the final obtained crystal structure is relatively coarse and segregated seriously, which is easy to cause fluctuations in carbon equivalent, so that the casting itself has a large Crack tendency, and due to the large size of the casting, it is easy to produce a hardened structure in the near-seam area of ​​the base metal during welding repair, and the proportion of the base metal melting into the first layer of weld metal is as high as 30%, resulting in the inclusion of weld metal. The high carbon content eventually leads to hot and cold cracks in the weld ...

Embodiment 2

[0053] The casting defect elimination method of this embodiment is further improved on the basis of Embodiment 1, and the local preheating in the third step is carried out with an oxyacetylene flame. The local preheating temperature is ≥100°C, and the preheating area is ≤100mm from the groove edge; the overall preheating temperature is ≥250°C. The cost of preheating with oxyacetylene flame is low, and the preheating equipment is simple and convenient to move, and the heating area and heating temperature are convenient to control; when using oxyacetylene flame for local preheating, the heat control within the preheating range is from small to large, And make the heat evenly distributed in the heated area to avoid excessive local temperature. The overall preheating is carried out by conventional methods. The preheating temperature should not be lower than the range described in this embodiment, otherwise the due effect of pre-welding preheating cannot be achieved.

Embodiment 3

[0055] The method for eliminating casting defects in this embodiment is further improved on the basis of Embodiment 2, and the fourth step adopts a metal carbon dioxide gas shielded welding method. The purity of carbon dioxide gas is ≥99.7%, and the water content of the gas is less than 0.005%. The welding wire is According to the characteristics of large steel castings, in order to strengthen the ability of resisting cold cracks and hot cracks after welding repair, and at the same time ensure that it matches the strength of the base metal, after many experiments and studies, the selected Welding wire is the most suitable, and the mechanical properties of the deposited metal of the welding wire are as follows:

[0056] Tensile strength (σ b )MPa

Yield strength (σ 0.2 ) MPa

Elongation (δ 5 )

≥500

≥420

≥22

[0057] During welding repair, the wind speed at the welding repair site should be less than 2m / s; the process parameters used when...

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Abstract

The invention discloses a casting defect eliminating method which belongs to the field of casting treatment. The casting defect eliminating method provided by the invention comprises five steps: defect cleanup, bevel preparation, weld preheating, welding repair and postweld treatment, wherein the defect cleanup refers to eliminating common surface defects by grinding, and common crack defects andgreats defects are subjected to a next step; the bevel preparation refers to forming a U-shaped bevel in the defected position and the bevel surface is a smooth curved surface; the weld preheating refers to carrying out local preheating to the common defects and integral preheating to the great defects; the welding repair refers to carrying out 1-2 layers of resurfacing welding along the side surface of a bevel, further fully welding the concave part in the resurfacing welding position and repeating the step until the whole bevel is welded to be full completely; and the postweld treatment refers to carrying out dehydrogenation treatment to the common defects after being welded and annealing treatment to the great defects after being welded. By improving the welding method and optimizing the process parameters when repairing different defects, the invention greatly reduces the probability of adverse influencing factors occurring in defect repair process, saves the time spent in defect repair and achieves the effect of cost saving while ensuring the qualified rate of casting repair.

Description

technical field [0001] The invention relates to the field of casting processing, more specifically to a casting defect elimination method Background technique [0002] Casting is a relatively early metal thermal processing technology mastered by humans. China has entered the heyday of bronze castings between 1700 BC and 1000 BC, and the technology has reached a very high level. Casting is a method of pouring liquid metal into a casting cavity adapted to the shape of the part, and then cooling and solidifying it to obtain a part or blank. Casting products are called castings. Castings have a wide range of uses and have been used in hardware and the entire mechanical and electronic industries. The number of casting parts specifically used in large machinery such as construction, engineering machinery, and metallurgical equipment is also increasing. [0003] At present, in the metallurgical industry, during the casting production of large steel castings (≥10-200 tons), due to ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B23P6/00
CPCB23P6/00
Inventor 江济张有飞边敦亭潘爱胜
Owner ANHUI MAGANG HEAVY MASCH MFG CO LTD
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