CN111215579A

CN111215579A - Casting process for preventing internal continuous thermal joint shrinkage cavity

Info

Publication number: CN111215579A
Application number: CN202010027981.4A
Authority: CN
Inventors: 黄德海; 姚建堂; 谈敏; 朱海永
Original assignee: Huzhou Nanfeng Machinery Manufacturing Co ltd
Current assignee: Huzhou Nanfeng Machinery Manufacturing Co ltd
Priority date: 2020-01-10
Filing date: 2020-01-10
Publication date: 2020-06-02

Abstract

The invention discloses a casting process for preventing an internal continuous thermal joint shrinkage cavity, which comprises the following steps of 1, manufacturing a sand shell by using precoated sand as a raw material; step 2, baking the sand shell, and then pouring the smelted molten steel into the sand shell; step 3, immediately placing the sand shell on a steel grid after the pouring is finished, introducing cold air or compressed air into the lower part of the grid, forcibly cooling the bottom and the inner cavity of the sand shell, and taking down the casting; and 4, performing shot blasting, riser cutting, heat treatment, secondary shot blasting and finishing on the casting to obtain a blank product. After the pouring is finished, the sand shell is quickly placed on the steel grating, cold air or compressed air is introduced into the lower part of the grating to forcibly cool the bottom and the inner cavity of the sand shell, so that continuous heat close to the bottom and the middle can be quickly solidified in an energy-saving manner, and shrinkage cavities and shrinkage porosity in the sand shell are eliminated.

Description

Casting process for preventing internal continuous thermal joint shrinkage cavity

Technical Field

The invention relates to a casting process for preventing an internal continuous thermal joint from shrinkage.

Background

The casting is a metal molding object obtained by various casting methods, namely, the smelted liquid metal is poured into a casting mold prepared in advance by pouring, injecting, sucking or other casting methods, and after cooling, the casting is subjected to subsequent processing means such as grinding and the like, so that the object with certain shape, size and performance is obtained.

In a conventional casting process, liquid metal is usually directly poured, and the thick part of a casting at an inner pouring gate and other parts with concentrated heat have unbalanced temperature, so that the defects of internal shrinkage porosity, shrinkage cavity and the like are easily generated during forming, and the casting is poor in quality and inconvenient to use. The flanges are arranged at the inlet and the outlet of each direct valve or machine barrel casting piece in precision casting, the inner pouring gates are arranged on the flanges and the body in process design, and the problem of shrinkage cavity is difficult to directly solve by the inner pouring gates in internal continuous thermal nodes, so that the rejection rate of casting is high, the casting cost is high, the economic benefit is low, and great troubles are brought to workers.

Disclosure of Invention

In view of the above problems, the present invention provides a casting process that prevents shrinkage of an internally continuous thermal segment, thereby effectively solving the problems noted in the background art.

The technical scheme adopted by the invention is as follows:

a casting process for preventing internal continuous thermal joint shrinkage cavity comprises the following steps:

step 1, manufacturing a sand shell by using precoated sand as a raw material;

step 2, baking the sand shell, and then pouring the smelted molten steel into the sand shell;

step 3, immediately placing the sand shell on a steel grid after the pouring is finished, introducing cold air or compressed air into the lower part of the grid, forcibly cooling the bottom and the inner cavity of the sand shell, and taking down the casting;

and 4, performing shot blasting, riser cutting, heat treatment, secondary shot blasting and finishing on the casting to obtain a blank product.

Preferably, the step 1 comprises the following steps:

step 1a, selecting a corresponding mold according to the structure of a sand shell casting mold, and then installing the mold on a core shooter;

step 1b, heating the die to 180-200 ℃ by adopting a thermocouple;

step 1c, keeping the mold at 180-200 ℃, blowing the mold cavity by adopting an air gun to spray compressed air, and removing foreign matters in the mold cavity;

step 1d, uniformly spraying a shell-making release agent on the mold cavity by using an air-spraying pot;

step 1e, injecting the precoated sand into a mold through a core shooter at the temperature of 200 ℃, and curing for 180-220 seconds to prepare a sand shell;

step 1f, uniformly spraying the coating for spraying on the inner surface of the sand shell by using a spray gun, and controlling the temperature of the sand shell to be more than or equal to 60 ℃ when the spraying is finished;

and step 1g, standing the sand shell for 90-120 minutes to obtain a finished sand shell.

Preferably, the specific operation of step 2 is as follows: and (3) baking the sand shell prepared in the step (1) for 3-4 hours at 150-200 ℃ by using a baking furnace, pouring the smelted molten steel into the sand shell, and controlling the pouring time within 20 min.

Preferably, the specific operation of step 4 is as follows: firstly, performing shot blasting on a cast by using a shot blasting machine for 15-20 minutes, and cutting off redundant risers of the cast after floating sand on the surface is cleaned; then heating the casting with the redundant dead heads removed to 900 ℃ by using a heat treatment furnace, and preserving heat for 4 hours for heat treatment; and after the heat treatment is finished, performing secondary shot blasting treatment on the casting for 30-40 minutes by using a shot blasting machine, cleaning the surface of the casting, and finishing local defects on the surface of the casting by using a grinding machine to obtain a blank product.

The invention can only arrange the inner gates at the thick flange, thereby reducing the number of the inner gates and improving the yield.

After the pouring is finished, the sand shell is quickly placed on the steel grating, cold air or compressed air is introduced into the lower part of the grating to forcibly cool the bottom and the inner cavity of the sand shell, so that continuous heat close to the bottom and the middle can be quickly solidified in an energy-saving manner, and shrinkage cavities and shrinkage porosity in the sand shell are eliminated.

Detailed Description

The present invention is described in further detail below with reference to specific examples.

Example 1

step 1, manufacturing a sand shell by using precoated sand as a raw material:

step 1b, heating the die to 180-200 ℃ by adopting a thermocouple;

step 1g, standing the sand shell for 90-120 minutes to obtain a finished sand shell;

step 2, baking the sand shell, and then pouring the smelted molten steel into the sand shell:

baking the sand shell prepared in the step (1) for 3-4 hours at 150-200 ℃ by using a baking furnace, pouring the smelted molten steel into the sand shell, and controlling the pouring time within 20 min;

step 4, performing shot blasting, riser cutting, heat treatment, secondary shot blasting and finishing on the casting to obtain a blank product:

firstly, performing shot blasting on a cast by using a shot blasting machine for 15-20 minutes, and cutting off redundant risers of the cast after floating sand on the surface is cleaned; then heating the casting with the redundant dead heads removed to 900 ℃ by using a heat treatment furnace, and preserving heat for 4 hours for heat treatment; and after the heat treatment is finished, performing secondary shot blasting treatment on the casting for 30-40 minutes by using a shot blasting machine, cleaning the surface of the casting, and finishing local defects on the surface of the casting by using a grinding machine to obtain a blank product.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. A casting process for preventing internal continuous thermal shrinkage cavity is characterized by comprising the following steps:

step 1, manufacturing a sand shell by using precoated sand as a raw material;

2. A casting process for preventing internal continuous thermal shrinkage cavity according to claim 1, wherein said step 1 comprises the steps of:

step 1b, heating the die to 180-200 ℃ by adopting a thermocouple;

3. The casting process for preventing internal continuous thermal shrinkage cavity of claim 1, wherein the step 2 is specifically performed as follows: and (3) baking the sand shell prepared in the step (1) for 3-4 hours at 150-200 ℃ by using a baking furnace, pouring the smelted molten steel into the sand shell, and controlling the pouring time within 20 min.

4. The casting process for preventing internal continuous thermal shrinkage cavity of claim 1, wherein the specific operation of step 4 is as follows: firstly, performing shot blasting on a cast by using a shot blasting machine for 15-20 minutes, and cutting off redundant risers of the cast after floating sand on the surface is cleaned; then heating the casting with the redundant dead heads removed to 900 ℃ by using a heat treatment furnace, and preserving heat for 4 hours for heat treatment; and after the heat treatment is finished, performing secondary shot blasting treatment on the casting for 30-40 minutes by using a shot blasting machine, cleaning the surface of the casting, and finishing local defects on the surface of the casting by using a grinding machine to obtain a blank product.