ductile iron pipe
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Centrifugally cast ductile iron pipe is a kind of spheroidal graphite cast iron manufactured by centrifugal spinning process. The pipe which can convey many fluid media such as water and gas, are widely used in various pipeline projects for metallurgy, mine , water conservancy, petroleum and urban public facilities. Being iron in nature while having properties od high strength, good toughness, corrosion resistance etc as steel, they are the sustitutes for traditional cast iron pipes and common steel pipes. The pipe are produced with high straightness, high surface finish and high size accuracy, even wall thickness, fine machancial properties and hard external coating. Flexible push-on joint and rubber gasket are used resulting in a convenient installation of pipes.
Technical wquipment:1. Hot mould centrifugal cast machine with multi working position . 2. Water-cooling mould centrifugal cast machine.
1. technological process by water-cooling metal mould
cupola(冲 天 炉 ) ---induction furnace (中 频 炉 ) ---spheroidizing ( 球 化 处 理 ) ---spectral analysis (光 谱 仪 成 分 检 测 分 析 ) ---water-cooling metal mould centrifugal casting machine (水 冷 金 属 型 离 心 浇 注 ) ---annealing treatment (退 火 处 理 ) ---(zinc coating喷 锌 ) ---dressing of socket and spigots (承 插 口 整 理 ) ---hydrostatic test (水 压 试 验 ) --
---cement lining (水 泥 内 衬 ) ---cment curing (养 生 ) ---bitumen coating (外 表 面 喷 涂 沥 青 )
air tightness test (气 密 试 验 ) drilling of flange (法 兰 钻 空 )
---trade mark painting (喷 涂 商 标 ) parking and warehousing (包 装 入 库 )
2. technological process by hot mould
cupola---induction furnace---spheroidizing---spectral analysis---hot mould centrifugal casting machine with multi-working position(热 模 法 离 心 浇 注 成 型 ) ---annealing treatment---short blast (抛 丸 ) (zinc spraying喷 锌 ) ---dressing of sockets and spigots---hydrostatic test---
---cement lining---cment curing---bitumen coating
air tightness testdrilling of flange
------trade mark paintingparking and warehousing
Properties of the products
Ductile cast iron, also known as Nodular graphite cast has following excellent properties:
1. high strength and toughness comparable to steel, to withstand high pressure.
2. high ductile to withstand impact.
3. good corrosion resistance similar to grey cast iron.
4. high flexibility for deflection.
5. easy machinability.
These superior characteristics of ductile cast iron are mainly due to its microstructure, which has a spheroidal shape of graphite I the metal matrix.
In grey cast iron however, graphite is found in a flaky shape , which has the effect of cotting the iron matrix and making it become brittle and easy crack.
(1) tensile strength and elongation
(2) hydrostatic test
(3) internal lining
thickness of internal lining
DN Thickness of cement lining Minimum average thickness Minimum value at any point
80~~~300 3 2.5 1.5
350~~~600 5 4.5 2.5
700 6 5.5 3.0
(4) (metallic zinc coating:
When metallic zinc spray is applied , the weight of the zinc layer is not lower than 130g/m2 with minimum weight at anywhere being 100 g/m2. . When zinc rich paint applied, the weight of the zinc layer is not lower than 150 g/m2 with minimum weight at anywhere being 130 g/m2.
(5) external coating :
the thickness of bitumen coating is not lower than 705m in average and not lower than 505m at any point.
The ductile iron pipes are in accordance with National Standard GB1329591<<ductile iron pipes, fittings and accessories for water or gas applications>>, and International Standard ISO253198<< ductile iron pipes, fittings and accessories for water or gas applications>>.