CN-116352042-B - Method for improving surface quality of spheroidal graphite cast iron pipe

CN116352042BCN 116352042 BCN116352042 BCN 116352042BCN-116352042-B

Abstract

The method for improving the surface quality of the nodular cast iron pipe comprises (1) spraying a release agent on the inner wall of a pipe die by adopting a spraying method instead of a brushing method before centrifugal casting, waiting for drying moisture in the release agent after one or more layers are sprayed, and then spraying for the next round, wherein the spraying is carried out repeatedly until the required spraying thickness is reached; the casting process adopts the mode of sleeving a slag blocking ring at the end part of the socket end core to improve the mechanical property and the density of the inner surface of the spheroidal graphite cast iron pipe by combining an online spheroidizing process, prevents slag inclusion and looseness of the inner surface of the socket, and (2) controls the preheating temperature of the spheroidal graphite cast iron pipe in a specified range when the surface is sprayed with zinc, and supports the spheroidal graphite cast iron pipe from the inner sides of two ports of the spheroidal graphite cast iron pipe by utilizing a tip type rotary chuck when the outer surface of the spheroidal graphite cast iron pipe is sprayed with an anti-corrosion layer and/or a heat preservation layer, thereby ensuring that the outer surface of the spheroidal graphite cast iron pipe is not contacted with other parts. The invention adopts multi-step measures to cooperatively improve the surface quality of the nodular cast iron pipe from two links of casting and spraying.

Inventors

ZHANG TONG
LI CHAOGANG
Liu Baopen
YANG YINGYING
LIU KEYONG
LIU CHUNGUANG

Assignees

国铭铸管股份有限公司

Dates

Publication Date: 20260512
Application Date: 20230410

Claims (9)

1. A method for improving the surface quality of a ductile iron pipe, comprising: (1) Prevention and elimination of surface casting defects Spraying a release agent on the inner wall of the pipe die by adopting a spraying method instead of a slurry brushing method before centrifugal casting, waiting for drying moisture in the release agent after spraying one or more layers, and then spraying for the next round, and spraying repeatedly for a plurality of rounds until reaching the required spraying thickness, wherein the evenness of the outer surface of the nodular cast iron pipe is improved by uniformly spraying the release agent, and the pits on the outer surface are reduced; the casting procedure adopts a mode of sleeving a slag blocking ring at the head part of the end core of the bell mouth and combines an online spheroidizing process to improve the mechanical property and the compactness of the inner surface of the spheroidal graphite cast iron pipe, and prevent slag inclusion and looseness of the inner surface of the bell mouth; (2) Prevention and elimination of surface spray defects Controlling the preheating temperature of the spheroidal graphite cast iron pipe to be in a specified range when the surface is sprayed with zinc, and supporting the spheroidal graphite cast iron pipe from the inner sides of two ports of the spheroidal graphite cast iron pipe by using a tip type rotary chuck when the anticorrosive coating and/or the heat preservation layer is sprayed on the outer surface of the spheroidal graphite cast iron pipe, so as to ensure that the outer surface of the spheroidal graphite cast iron pipe is not contacted with other parts; the prescribed range of the preheating temperature is 150-200 ℃.
2. The method for improving the surface quality of the ductile iron pipe according to claim 1, wherein the required spraying thickness is 0.8-2.5mm.
3. A method for improving the surface quality of a ductile iron pipe according to claim 1 or 2 characterized in that the main component of the release agent is zircon powder.
4. The method for improving the surface quality of the nodular cast iron pipe according to claim 1, wherein the slag blocking ring is a nodular cast iron circular ring and is sleeved on a position, which is easy to cause slag inclusion and loosening, of the inner wall of the nodular cast iron pipe corresponding to the socket end core head.
5. The method of claim 4, wherein the spheroidal graphite cast iron ring is a solid ring or is formed by wrapping spheroidal graphite cast iron with a fine crushed material.
6. The method of claim 4 or 5, wherein the on-line spheroidizing process is a spheroidizing process of casting liquid in a ladle on a ladle carriage.
7. The method of claim 6, wherein the on-line spheroidizing process is operated by means of a moving spheroidizing stand on a ladle carriage.
8. The method for improving the surface quality of a ductile iron pipe according to claim 1 wherein the predetermined range of the preheating temperature is 170-190 ℃.
9. The method of claim 8, wherein the top-type spin chuck is also used to support the tube during zinc spraying.

Description

Method for improving surface quality of spheroidal graphite cast iron pipe Technical Field The invention relates to the technical field of centrifugal casting of spheroidal graphite cast iron pipes, in particular to a method for improving the surface quality of spheroidal graphite cast iron pipes. Background The spheroidal graphite cast iron pipe can be used as a fluid conveying pipeline or a heating pipeline in water supply and drainage engineering, and is generally produced by a centrifugal casting process in industry, for example, patent literature with publication number of CN1119570A and name of a method for producing the centrifugal spheroidal graphite cast iron pipe introduces a heating pipe die, heat insulation coating is sprayed on the inner wall of the pipe die, then the spheroidal graphite cast iron pipe is centrifugally cast, and the spheroidal graphite cast iron pipe is transferred into an annealing kiln for annealing, so that a basic flow of the spheroidal graphite cast iron pipe with higher elongation is obtained, and the spheroidal graphite cast iron pipe is also required to be sprayed with different protective layers or functional layers according to working condition requirements and technical requirements of customers before leaving a factory, so that whether the spheroidal graphite cast iron pipe meets quality standards depends on surface casting quality and surface spraying quality to a great extent. In long-term production, the surface casting quality problems of ductile cast iron pipes, which are easy to repeatedly appear, comprise more pits on the outer surface, poor flatness, slag inclusion and partial looseness on the inner surface, and the like, and the surface spraying quality problems comprise uneven thickness of a zinc spraying layer, easy falling of a spraying layer, easy occurrence of mechanical indentation on an outer surface anti-corrosion layer and/or an insulation layer, and the like, which are not eradicated all the time. Disclosure of Invention In order to solve the problems in the background technology, the invention provides a method for improving the surface quality of a spheroidal graphite cast iron pipe, which starts from two links of casting and spraying, adopts a multi-step effective means to prevent and eliminate surface casting defects and surface spraying defects, and cooperatively improves the surface quality of the spheroidal graphite cast iron pipe. The technical scheme of the invention is as follows: A method for improving the surface quality of a ductile iron pipe, comprising: (1) Prevention and elimination of surface casting defects Spraying a release agent on the inner wall of the pipe die by adopting a spraying method instead of a slurry brushing method before centrifugal casting, waiting for drying moisture in the release agent after spraying one or more layers, and then spraying for the next round, and spraying repeatedly for a plurality of rounds until reaching the required spraying thickness, wherein the evenness of the outer surface of the nodular cast iron pipe is improved by uniformly spraying the release agent, and the pits on the outer surface are reduced; the casting procedure adopts a mode of sleeving a slag blocking ring at the head part of the end core of the bell mouth and combines an online spheroidizing process to improve the mechanical property and the compactness of the inner surface of the spheroidal graphite cast iron pipe, and prevent slag inclusion and looseness of the inner surface of the bell mouth; (2) Prevention and elimination of surface spray defects When the preheating temperature of the spheroidal graphite cast iron pipe is controlled to be in a specified range and an anti-corrosion layer and/or an insulating layer is sprayed on the outer surface of the spheroidal graphite cast iron pipe, the spheroidal graphite cast iron pipe is supported from the inner sides of two ports of the spheroidal graphite cast iron pipe by using a tip type rotary chuck, so that the outer surface of the spheroidal graphite cast iron pipe is ensured not to be contacted with other parts. Further, the required spraying thickness is 0.8-2.5mm. Further, the main component of the release agent is zircon powder. Further, the slag blocking ring is a spheroidal graphite cast iron ring and is sleeved on the part, which is easy to cause slag inclusion and loosening, of the spheroidal graphite cast iron pipe inner wall corresponding to the bell mouth end core head. Further, the spheroidal graphite cast iron circular ring is a solid ring or is formed by wrapping spheroidal graphite cast iron fine crushed materials with iron sheets. Further, the online spheroidizing process is a spheroidizing process of casting liquid in a ladle on a ladle trolley. Further, the on-line spheroidization process operates with a moving spheroidization frame on a ladle carriage. Further, the prescribed range of the preheating temperature is 150 to 200 ℃. Further, the prescribed ran