Malleable pipe fittings knowledge

by | Jan 22, 2022 | Industry Knowledge

Malleable iron pipe fittings were invented in 1940 and were developed and promoted by Americans. At that time, the pipe fittings were mainly used in the heat dissipation and heating system of steam engines, and the hot-dip galvanized malleable iron fittings were used for outdoor electrical pipes.

The purpose of pipe fittings is to connect two different pipe parts together and guide the movement of gas and liquid. It is to connect different pipes together by means of screw connection.

MI fittings Standard:

In 1901, the most powerful country where the sun never sets, the United Kingdom established the British Engineering Standards Committee, referred to as BSI. This association has formulated a large number of standards in various industries, the most famous of which is the ISO9000 series of standards.

For malleable iron pipe fittings, the earliest standard is In 1922, the BS143 standard, which had preliminary regulations on pipe fittings, also included American standards in order to demonstrate its strength. Germany failed in World War II in 1945, but after witnessing the strength of Germany, the BSI organization incorporated the German standard on the basis of BS143 and established the BS1256 standard.

In 1986, the two standards were merged and collectively referred to as BS143&1256, and the former British colonial countries are still implementing this standard. The European Union was established in 1993, and in 1995 the European Union decided to adopt British Standards. So BS143&1256 was officially renamed BS EN10242 after minor revisions. This standard is currently the most widely used standard number in the world.

As a rising star in the United States, in 1918, the American National Standards Institute was established. Abbreviated as ANSI, in 1921, the American Society of Mechanical Engineering (ASME), a branch of this society, drafted the standard B16C-1939. This standard only specifies the relevant parameters of 150-pound pipe fittings. In 1932, the Association of American Railroads (AAR) applied to ANSI to formulate a 300-pound pipe. The standard code for pipe fittings is ASA B16.19-1951.

In 1961, the two standards were merged, and the standard number was ASA B16.3-1963. In 1982, the standard was upgraded to ANSI/ASME B16.3- In 1985, this standard number is the current American standard. At present, only the United States has implemented the most thorough implementation, and neighbouring countries have only implemented the thread standards.
The ISO standard is an international standardization association established in 1926 by developed countries, the United States, Britain and other countries, and currently has 165 members. The main purpose is not to set standards independently, unified standardization, pipe fitting standard ISO49, sealing thread standard ISO7-1, non-sealing thread ISO228, the material standard ISO5922 These standards are the standard numbers that appear more frequently in our daily use.
In 1982, China began to formulate its own standard, GB/T3287-1982. At that time, BS143&1256 was basically adopted. In 2000, the standard was corrected and the European Union’s EN10242 standard was adopted, and the standard was updated. The new version of the standard number The standard is GB/T3287-2000. This time, it was drafted by Jinan Meide, Tianjin Tongbao (HE), Jiangxi Ganma, Hebei Jianzhi, other associations, thread tool processing plants, quality inspection centres and other institutions. Formulated and announced by the Product Standardization Technical Committee.

CountryCountry Malleable Iron Pipe Fitting Standard Sealed Pipe Thread Standard Unsealed Pipe Thread Standard Material Standard
European UnionEN10242EN10226EN ISO228EN1562
UKBS143&1256BS EN10226BS2779BS6681
GermanyDIN2950DIN2999DIN ISO228DIN1692
FranceNF E03-004NF E03-005NF A32-701
JapanJIS B2301JIS B 0203JIS B0202JIS G5705
BrazilNBR 6943NBR NM-ISO7-1ISO228NBR6590
IndiaIS 1879IS 554IS 8999IS 14329
The corresponding standards

The corresponding standards of each country are basically equivalent. The content is basically the same, with only minor deletions in individual details.
The regions corresponding to American Standard product standards are mainly North America and the Philippines.
German standard products are mainly German.
Russian standard products are mainly from Russia and neighboring countries, such as Ukraine, Kazakhstan, Belarus, etc.


The raw materials are scrap iron and scrap steel. We strictly control the quality of raw materials from entering the factory to ensure product quality. The sulfur content and phosphorus content of scrap iron and steel are not more than 0.10% and 0.2% respectively, and the manganese content and metal chromium content are not more than 0.8% and 0.08% respectively. For bread iron, we mainly detect five elements, carbon, silicon, manganese, sulfur, and phosphorus, whose contents are >3.4%, 0.8%-1.0%, <0.2%, <0.05%, <0.05%. We conduct random inspections and tests on the raw materials of each train. Only after qualified can enter the factory. Unqualified batches of vehicles will be returned.
Malleable cast iron is divided into several grades according to the mechanical properties. For example, KTH300-06, KTH330-08, KTH350-10, etc. The meanings of the letters in these grades are: KTH means black-heart malleable cast iron, 300 means tensile strength is 300MPa, 06 means elongation is 6%. The current export commitment is KTH330-08 material. In fact, some products can reach KTH350-10
The materials used for the production of malleable steel pipe fittings according to international standards and EU standards are black-heart malleable cast iron grades KTH300-06.


At present, the most widely used is inch, which is the British standard. The first 1 inch represents the length of a thumb section. Later, because everyone’s thumb is different, the 14th century King Edward changed the rule to a handful of wheat ears, and chose 3 pieces. The largest one is 1 inch in a row, and the approximate size is 25.4 mm. This custom has been used to this day.
There is another name for size called metric size, which is in millimeters, and 1 inch is also called 25.
There is also a common name in China, that is, 1 inch is divided into 8 parts, that is, 25.4 mm is divided into 8 parts on average, and each part is called 1 point. Usually, 4 points refers to 12.7 mm, which is 12.7 mm in inches. 1/2″, 15 in metric size.

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At present, our company produces three series of pipe fittings.

National standard square edge

The overall dimensions of this series of pipe fittings conform to ISO standards and EN standards, and all relevant certifications are basically this series, so all products of the national standard series pipe fittings are cast with FM and UL certification marks, and the thread processing size conforms to the standard , so it can process American standard thread and British standard thread. Russian standard thread, German standard thread, etc. This series of pipe fittings are mainly exported to the former colonial countries of European powers from the 15th to the 18th century, Australia, New Zealand, Saudi Arabia, Israel, Canada, Singapore, Malaysia, Mexico, Brazil, etc.;

Enterprise standard round edge & enterprise standard square edge

It belongs to our company’s own design and research and development. The dimensions of the two series of products are exactly the same, only the edges are different. This type of pipe fittings use less material, but the mechanical properties and tensile strength exceed the national standards, and have been awarded by the Ministry of Agriculture. The name of the new pipe fittings. The main reason for high performance is the use of good raw material ratio technology and the application of stable annealing technology. The weight of this kind of pipe fittings is 10-15% lighter than that of the national standard series, and the price is 5-8% cheaper than that of the national standard series. So it is more favored by the market. The round-edged series are mainly exported to Europe, and the square-edged series have been sold to five continents. Compared with the national standard pipe fittings, except for the type and size that are slightly smaller than the national standard pipe fittings, there are differences in trademark making. The trademark of the national standard pipe fittings is concave, and the trademark of the enterprise standard square edge pipe fittings is convex.

Mechanical behavior:

The materials used for the production of malleable iron pipe fittings according to international standards and EU standards are black-heart malleable cast iron grades KTH300-06. In order to make the branch pipe fittings have good mechanical properties, the whole process from product design to delivery is completed by the company itself, without any external cooperation. Malleable cast iron of grade KTH350-10 is used in the manufacture.
All Jianzhi products are smelted in electric furnaces, and the materials are carefully screened before being put into the furnace to eliminate unqualified products, strictly control the particle size (length) of the charge, and strictly follow the technical specifications to ensure the stable and uniform content of various elements in the molten iron. In order to ensure everything is safe, an on-line carbon and silicon analyzer for molten iron is set up in front of the furnace to conduct pre-furnace analysis of molten iron at any time. Through strict control of the smelting process, the uniformity and stability of various elements in the material are effectively ensured, the element content in the molten iron is controlled within a very reasonable range, and the two harmful elements, sulfur and phosphorus, are firmly controlled below 0.12% and 0.14%, respectively. The harmful elements are more than 20% lower than the materials used by other domestic manufacturers.
The heat treatment process is a key process in the production of malleable steel. The annealing furnace we use is the most advanced tunnel heat treatment furnace and electric annealing furnace in China. The continuous combustion and continuous operation are adopted and the furnace temperature is automatically controlled by a microcomputer, which not only saves manpower and material resources The resources meet the environmental protection requirements, and more importantly, the quality is guaranteed.
According to the requirements of quality management, we imported advanced spectrometers from Germany, equipped with advanced testing equipment such as microcomputer automatic control carbon and sulfur analyzer, microcomputer servo hydraulic universal testing machine, etc., to monitor and measure the production process at any time. The results of the material mechanical properties test show that the tensile strength is all over 350MPa; the elongation rate is all over 10%, and the qualified rate of mechanical properties is 100%.
Mechanical properties and tensile strength are relatively important indicators, but they are almost impossible for customers to measure, because the samples tested are either tensile rods or blanks, and customers cannot buy these things. Therefore, in some countries, the finished pipe fittings will be tested. For example, according to the Brazilian standard, the flattening rate of small pieces under 2 inches is 10% of that of pipe fittings, and the flattening rate of small pieces above 2 inches is 5% of that of pipe fittings, and the pressing speed is 1.5mm/s per second. Check for cracks after flattening. No cracks with more than two buttons are qualified.

Qualification rate of pipe fittings:

In fact, the difficulty of the casting industry is relatively low, and the gap between the process and technology is not very large. The quality of the product mainly depends on the level of management. In terms of quality management:
Invented the “Chain-type Quality Management Achievement” and won the “First Prize of Enterprise Management Modernization Innovation Achievement” issued by the Ministry of Agriculture. The concept of chain quality management is to regard the next process as the user. The quality of the products must be strictly controlled in each process, and the quality of the products transferred from the previous process must be strictly checked during the operation of the next process, and those found to be unqualified in the previous process must be eliminated. The unqualified products detected in the previous process will be rewarded, and those found to be unqualified in the next process will be punished. In this way, the next process controls the quality of the previous process, one link is closely linked to the other, forming a complete quality management chain.
Replaced by the actual operation:

  1. There is an inspection workshop behind each process of Jianzhi products. All products are manually inspected. Doing so avoids substandard products from entering the next process.
  2. All finished pipe fittings are also tested for air tightness before leaving the factory. The test pressure is 0.7Mpa air pressure. Make sure the product is 100% leak-proof.
  3. In terms of sampling inspection, the products must first be sampled by the factory-level sampling inspectors, and then the quality department will conduct sampling inspections on the batch of products again. Before packaging, the packaging personnel will conduct sampling inspections again. A batch of products is subject to 4 sampling inspections.
  4. Traceability, the mold number is printed on our pipe fittings, and the inspector packer number and packaging date are printed on the packaging. According to the company’s internal documents, all products from the company can be traced back to the relevant workshop and relevant personnel. Make sure that the responsibility goes to the person.
  5. According to the traceability, the CEO of our company invented the chain management method, which means that all links are connected in series, for example, if there are products without threads on the market. Then punish the quality inspection department first, and then punish the packaging workshop, finished product inspection workshop, and machining workshop. If a product without threads is found by the packaging workshop, the packaging workshop will punish the finished product inspection workshop and the machining workshop. Of course, punishing others will get a 40% commission. In addition, in order to monitor whether the punishment is implemented, or if there is an unfair phenomenon, the company has also established an enterprise management department, which is responsible for comprehensively supervising all aspects of the company. Ensure the efficient operation of the management system.

Founded in 1982, Jianzhi is a leading manufacturer and supplier of cast iron pipe fittings. Till now, Jianzhi has about 4,500 employees and more than 350 technical engineers with distributors covering over 100 countries around the world.

As our main products, Galvanized Pipe Fittings and Black Pipe Fittings are widely used in various large-scale projects, such as Beijing National Stadium ( the Bird’s Nest), Water Cubic (Beijing National Aquatics Center), Beijing Daxing International Airport, CCTV underpants etc.