The production process of IF brand malleable cast iron threaded pipe fittings is divided into 11 major steps: coated sand molding, melting, pouring, annealing, polishing, rectification, grinding, trimming, galvanizing, threading, and packaging.
1.Coated Sand Molding
Casting is a molding method that involves melting metal, making molds, pouring the molten metal into the molds, and allowing it to cool and solidify to obtain castings of a certain shape and properties. There are many casting methods, often classified into sand casting and special casting.
Fluid Tech Group’s cast iron threaded pipe fittings are produced using the sand casting method. Sand casting involves designing and producing patterns and core boxes based on the product’s shape and dimensions, preparing molding sand and core sand, creating the mold using the pattern and molding sand, creating the cores using the core box and core sand, assembling the mold, pouring the molten metal into the mold, and obtaining the casting after cooling and solidification. Molding refers to the process of making the mold within the casting procedure. To ensure the dimensional accuracy of the molds, Fluid Tech Group has established its own pattern production and repair workshops. All patterns and core boxes are independently designed and produced. Furthermore, Fluid Tech Group’s pattern production is entirely completed using high-precision CNC machine tools and automated machining centers, placing its technical capability and equipment investment among the top in the domestic industry. To meet overseas market demand, the company has developed new molds for IF brand cast iron pipe fittings.
Regarding the use of molding sand, Fluid Tech Group products exclusively use the highest specification Grade 1 water-washed sand to avoid contamination with mud and stones, ensuring a smooth mold surface and mold stability.
2.Melting
Melting refers to the process of heating raw metal materials to a molten state in preparation for pouring during the casting process. Fluid Tech Group’s melting process exclusively uses electric furnaces. Firstly, this avoids the high air pollution caused by fuel combustion in traditional cupola furnaces, complying with national environmental standards. Secondly, it ensures uniform heating and consistent temperature of the material during melting, preventing casting defects caused by undercooling or overheating of the molten metal. Simultaneously, Fluid Tech Group has introduced advanced online carbon equivalent analyzers to analyze the carbon content of the iron-carbon alloy during melting, decompose cementite, and ensure the metallic composition and properties of the castings.
3.Pouring
Pouring refers to the process of introducing the molten metal into the mold, where it cools and solidifies to form the casting.
4.Annealing
Annealing is a metal heat treatment process that involves slowly heating the metal to a certain temperature, holding it for a sufficient time, and then cooling it at a suitable rate. The purposes are to reduce hardness and improve machinability; eliminate residual stresses, stabilize dimensions, reduce the tendency for deformation and cracking; refine grain structure, adjust the microstructure, and eliminate structural defects. Precisely speaking, annealing is a heat treatment process for materials, including both metallic and non-metallic materials. Furthermore, the purposes of annealing new materials can differ from those of traditional metal annealing.
Graphitization annealing refers to the decomposition of cementite (Fe₃C) and the elimination of flake graphite structures (as found in gray iron) during the annealing process. This results in a matrix of ferrite + temper carbon (nodular aggregates of graphite). If the annealing process is immature, remnants of gray iron (flake graphite structure) can remain in the core, presenting a gray fracture surface – what we call ‘gray spots’.
Additionally, due to undercooling during the solidification of the molten metal, differences in grain growth size can occur. Annealing refines the grain size, improving the mechanical properties of the castings. Volume changes caused by allotropic transformation during the solidification of the molten metal generate internal stresses. The annealing process can eliminate these residual internal stresses, stabilize dimensions, and reduce the tendency for deformation and cracking. The annealing step for cast iron threaded pipe fittings is performed to achieve the aforementioned objectives.
If the material of the cast iron threaded pipe fittings is ductile iron, the annealing process is not required.
5.Polishing
The castings obtained after shakeout first undergo surface polishing to produce semi-finished products with smooth surfaces. Fluid Tech Group uses centrifugal polishing machines with steel balls as the polishing media. Inside the centrifugal polisher, the steel balls repeatedly grind against the castings, smoothing their appearance.
6.Rectification
After polishing, castings identified through inspection as not meeting roundness requirements or having surface profiles that do not conform to specifications undergo a rectification process to bring their shape into compliance.
7.Grinding
After rectification, castings undergo a grinding process to remove larger casting residues remaining on the surface after polishing, aiming for an aesthetically pleasing appearance.
8.Trimming
Because casting patterns are typically designed for multiple cavities per mold, castings often have gates and connecting channels designed into the pattern, which create flash upon pouring. During the trimming step, these flashes on the internal and external surfaces of the castings are removed via machining.
9.Galvanizing
Fluid Tech Group’s galvanizing is divided into two processes: Hot-Dip Galvanizing and Electro galvanizing. The IF brand threaded pipe fittings from Fluid Tech Group adopt the sequence of galvanizing first, followed by threading. This avoids thread dimensional deviations caused by the galvanized layer, ensuring smooth installation. It also prevents potential damage to the threads from product collisions during the galvanizing process, further guaranteeing smooth installation during product use.
10.Threading
The castings prior to the threading process are referred to as semi-finished products. Threading involves machining the semi-finished products according to customer requirements to produce threads conforming to different national standards on the castings.
Common pipe threads mainly include the following: NPT, PT, G, etc.
1) NPT stands for National (American) Pipe Thread. It belongs to the American standard 60-degree tapered pipe thread, governed by standard ANSI/ASME B1.20.1. Cylindrical threads are usually denoted by NPS (National Pipe Straight), which is the American standard straight pipe thread – a parallel thread without taper. American standard threads are used in North America. The corresponding Chinese standard is GB/T 12716-1991.
2) PT (BSPT) stands for Pipe Thread. It is a 55-degree sealing tapered pipe thread, belonging to the Whitworth thread family. Its standard is BS 21, equivalent to the ISO 7-1 standard. Non-sealing cylindrical pipe threads are denoted by BSPP. It is mostly used in Europe and Commonwealth countries, commonly in the water and gas pipe industries. The taper is 1:16. The corresponding Chinese standard is GB/T 7306-2000. In China, this standard is generally written as ZG.
3) G is a 55-degree non-sealing pipe thread, belonging to the Whitworth thread family. The designation G represents cylindrical threads. The corresponding Chinese standard is GB/T 7307-2001.
Metric threads are specified by pitch, while American and British imperial threads are specified by the number of threads per inch. Metric threads have a 60-degree equilateral thread form, British imperial threads have an isosceles 55-degree thread form, and American threads have an isosceles 60-degree thread form. Metric threads use metric units (e.g., mm), while American and British imperial threads use imperial units (e.g., inch). IF brand fittings can be produced with NPT standard threads; they can also be manufactured according to customer requirements with BSPT thread standards; or they can be produced as IF brand threaded fittings with non-sealing threads.
To ensure the practical usability of the IF brand threaded fittings and enable smooth engagement of the pipe threads, Fluid Tech Group considers maximizing the internal cavity space during the design phase. The thread end is designed with a relief groove structure, and the internal threads are fully tapered through, ensuring performance during use.
11.Packaging
IF brand threaded pipe fittings are packaged in three different ways: woven bag packaging, carton packaging, and pallet packaging.
If woven bags are used for packaging IF brand threaded pipe fittings, approximately 1300 bags can be loaded into a 20ft container.
If cartons are used for packaging IF brand threaded pipe fittings, approximately 1010 cartons can be loaded into a 20ft container.
If pallets are used for packaging IF brand threaded pipe fittings, 24 pallets, containing 860 cartons of pipe fittings, can be loaded into a 20ft container.
