When steel and malleable cast iron pipe fittings are connected by thread, if the working pressure is high (but within 1.6Mpa), steel pipe fittings can be used.
The standard of stainless steel pipe fittings should include the type parameter standard of pipe fittings and the material standard of stainless steel pipe fittings. However, the material standards are either incomplete, or lack of quality technical requirements such as order requirements, inspection and approval rules, quality certification and so on. The standard matching of stainless steel pipe fittings is poor, which is often formulated from their respective positions and angles, rather than from the whole standard system of pressure pipes. In the selection of engineering, there are pipe standards, but there is no corresponding forgings or casting standards.
The feed iron pipe fittings are made of gray cast iron. There are two kinds of water supply cast iron pipe fittings, which are socket type and flange type. Their use is similar to that of malleable cast pipe. There are the following types: cross pipe, T pipe (including three bearing cross pipe, three plate cross pipe, four bearing cross pipe, four plate cross pipe, double bearing T pipe, double disk T pipe, three bearing pipe, three disk tube, double bearing single disk T pipe, single bearing double disk T pipe). 90 °bend, 45 °bend; fork pipe; B pipe; hydrant pipe; casing and so on. The main drainage cast iron pipe fittings are socket bending pipe, 90 °elbow, 45 °Y-shaped three-way, 90 °T-shaped three-way, 90 °TY three-way, oblique four-way, positive four-way, TY-shaped special-diameter three-way, special-diameter four-way, pipe hoop, T-shaped bottle mouth, 45 °elbow, Y-shaped special-diameter three-way, socket sweep, S-shaped water storage bending, P-shaped non-bending, floor leakage and so on.
Note: a variety of different joint pipe fittings can be made of different materials. At present, plastic joint pipe fittings have been widely used, because only with different materials, it will not be repeated here. The reality is that the standard of stainless steel pipe fittings forgings borrows the forgings standard of pressure vessels and does not take into account the differences between the two, such as welding, film inspection and so on. Steel pipe fittings are made of carbon steel, commonly known as cooked iron pipe fittings. It has good weldability and can be used in places where welding is needed, such as steel pipe hoops are often connected to steel equipment such as boilers or water tanks.
The type test standard of stainless steel pipe fittings is only specified in GB12459 and GB13401 standards, and the pressure calculation of blasting test of steel butt welded seamless stainless steel pipe fittings and steel plate bearing stainless steel fittings is stipulated, but there are no other type test standards or implementation standards to ensure the manufacturing quality of pipe fittings. In order to meet different uses and conditions, the structure of steel metal stainless steel pipe fittings is varied. Among them, elbow, three-way and different diameter pipe are the most used.

How to distinguish the authenticity of Maanshan Steel Pipe fittings?
Rapid Identification method of fake and inferior Pipe fittings “one knock, two look, three heats”
With the rapid development of economy in our country, the demand for malleable cast iron pipeline connectors (commonly known as Ma steel pipe fittings) for waterway, gas circuit and oil circuit is increasing day by day, and the quality requirements will be higher and higher. To judge the quality of a pipe fitting in Maanshan Iron and Steel Co., Ltd., the first thing is to see whether it meets the corresponding national standards (GB/T3287-2000).
However, some technical management, procurement and construction personnel suffer from little understanding of the national standards of Maanshan Iron and Steel Pipe fittings, it is difficult to judge the quality of Maanshan Steel fittings for a while, they urgently need a more intuitive and easy to carry atlas to help them identify. It is believed that the publication of this atlas will help you to improve the ability to identify the advantages and disadvantages of Maanshan steel pipe fittings, and prevent being deceived.
One knock: malleable cast iron pipe fittings are ductile casting products, such as tapping with external force, its surface if there are indentation or a small amount of deformation does not crack, it can show that its material performance is OK.
Second look: first look at the length of the thread, the general fake and shoddy product thread length is always very short. Second, galvanizing, GB/T3287-2000 galvanizing refers to the better corrosion resistance of hot-dip galvanizing, its process is to process the thread first hot-dip galvanizing, and then thread processing, so there is no zinc layer on the thread surface. But the fake inferior product carries on the electroplating galvanization or other coating treatment after the thread processing, its thread surface has the zinc layer (coating), its cost is much lower, the corrosion resistance is poor, after installed on the pipe, yellow water (rust water) will appear.
Sanping: it is bound to reduce the outer diameter, thin wall thickness and medium and long size of Ma steel pipe fittings, which are generally lighter than the national standard pipe fittings by more than 10%. As soon as we weigh the weight of our hands, we can distinguish between fake and inferior.

What is the essential difference between nodular cast iron fittings and gray cast iron?
Pig iron for nodular ink casting is also a kind of cast pig iron, but low sulfur and low phosphorus. Low sulfur makes carbon fully graphitized in iron. Before pouring molten iron (nodular pig iron), a certain amount of nodulizing agent (commonly used is ferrosilicon, magnesium, etc.) to make graphite in cast iron nodular. Because carbon (graphite) exists in cast iron matrix as sphere, the tensile strength, yield strength, plasticity and impact toughness of nodular cast iron are greatly improved by improving its cutting effect on matrix. And has the advantages of wear resistance, shock absorption, good process performance, low cost and so on. Now it has widely replaced malleable cast iron and some cast steel, forged steel parts, such as crankshaft, connecting rod, roll, automobile rear axle and so on.

Most or all of the carbon in cast iron exists as free flake graphite. The fracture is gray. It has good casting performance, good machinability, wear reduction, good wear resistance, simple melting ingredients, low cost, widely used in the manufacture of complex castings and wear-resistant parts.