How chemical elements affect the mechanical properties of steel pipe

How chemical elements affect the mechanical properties of steel pipe ?

How chemical compositions affect the mechanical properties of steel pipe ?



Carbon, a basic element, has the greatest influence on the properties of steel pipe. The influence of different carbon content on the properties of steel is different according to the content of impurity elements in the steel and the different cooling conditions after rolling. With the increase of carbon content in the steel, the hardness of carbon steel in the hot rolled state increases linearly, while the plasticity and toughness decrease. In the subeutectoid range, the influence of carbon on tensile strength is that the tensile strength increases with the increase of carbon content. While beyond eutectoid range, it decreases with the increase of carbon content. In addition, when carbon content increases, the corrosion resistance of carbon steel decreases, while carbon also makes carbon steel welding performance and cold processing (stamping, drawing) performance become worse.



The content of silicon in carbon steel is no more than 0.50%. Silicon is also a useful element in steel. In rimmed steel, silicon content is very low. Silicon is added to steel as a deoxidizing element. The silicon content in killed steel is generally 0.12 ~ 0.37%. Silicon increases the fluidity of molten steel. In addition to forming non-metallic inclusions, silicon is dissolved in ferrite. With the increase of silicon content, the tensile strength, yield point, elongation, surface shrinkage and impact toughness of the steel increased significantly.



In carbon steel, manganese is a beneficial element. Manganese is added to steel as an element for deoxidation and sulfur removal. For killed steel, manganese can improve the deoxidation effect of silicon and aluminum, and form manganese sulfide with sulfur, which can reduce the harm of sulfur in steel to a considerable extent. Manganese has a good effect on the mechanical properties of carbon steel. It can improve the hardness and strength of steel after hot rolling. The reason is that manganese melts into ferrite and causes solution strengthening. Therefore, the manganese content of each furnace should be controlled strictly and stably according to the technical requirements in the refining process.



Generally speaking, phosphorus is a harmful element in steel. It comes from raw materials such as ore and pig iron. Phosphorus can improve the strength of steel, but reduce the plasticity and toughness, especially make the brittle transition temperature of steel rise sharply, that is, increase the cold brittleness (low temperature brittleness) of steel. Due to the harmful effects of phosphorus, and the large segregation of phosphorus, the content of phosphorus should be strictly controlled.

However, in the steel with low carbon content, the damage of phosphorus is relatively small. In this case, phosphorus can be used to improve the strength of steel. In addition, other beneficial effects of phosphorus are utilized where appropriate, such as increasing the atmospheric corrosion resistance of steel, such as container steel; Improve magnetism, such as electrical silicon steel; Improve the machinability of steel and reduce the bond of hot rolled sheet.



Generally speaking, sulfur is also a harmful element, which mainly comes from the raw material and combustion product, sulfur dioxide. The greatest harm of sulfur is that it causes steel to crack during hot working, which is called hot embrittlement. Sulfur can improve the machinability of steel, which is the beneficial effect of sulfur.



Nitrogen in steel comes from the furnace charge, and the molten steel absorbs nitrogen from the furnace gas and atmosphere during smelting and casting. Nitrogen causes quenching aging and deformation aging of carbon steel, which has a significant effect on the properties of carbon steel. Due to the aging effect of nitrogen, the hardness and strength of steel are increased, but the plasticity and toughness decrease, especially under the condition of deformation aging. Therefore, for ordinary low alloy steel, the aging phenomenon is harmful, thus nitrogen is a harmful element. But for some fine grain steels and vanadium and niobium steels, nitrogen becomes a beneficial element due to the effect of nitride on grain refinement. In addition, as an alloying element, nitrogen is used in stainless acid-resistant steel. In addition, the nitriding treatment method can make machine parts obtain excellent comprehensive mechanical properties, thus prolonging the service life of the parts.



Hydrogen in steel is absorbed from either corrosive water-bearing furnace charge or a furnace gas containing steam. Hydrogen is very harmful to steel. One is to cause hydrogen embrittlement, that is, under the action of the ultimate stress of steel, after a certain period of time, in the absence of any warning under the circumstances of sudden fracture, often cause disastrous consequences. The second is to cause a large number of fine crack defects inside the steel – white dot, smooth silver dot in the steel vertical end face. After the pickling, the end face show more hair filaments crack. White dot makes the elongation of steel significantly decreased, especially the end shrinkage rate and impact toughness reduce more, sometimes may be close to zero. Therefore, steel with white dot is not available. This defect occurs mainly in alloy steel.


Oxygen(O)and other nonmetal inclusions 

The solubility of oxygen in steel is very low, and almost exists in steel in the form of oxide inclusion, such as FeO, AL2O3, MnO, CaO, MgO, etc. In addition, there are FeS, MnS, silicates, nitrides and phosphates in steel. These inclusions break the continuity of the steel matrix and often become the starting point of cracks under both static and dynamic loads. The various states of these non-metallic inclusions affect the properties of steel to varying degrees, especially the plasticity, toughness, fatigue strength and corrosion resistance of steel. Therefore, nonmetallic inclusions should be strictly controlled.



One important kind of plastic raw material----recycled/virgin HDPE granules high density polyethylene/ PE granules

One important kind of plastic raw material—-recycled/virgin HDPE granules high density polyethylene/ PE granules

High Density Polyethylene (HDPE), also known as low-pressure Polyethylene, is a kind of High crystallinity, non-polar surface shows a certain degree of translucent shape.PE has excellent resistance to most domestic and industrial chemicals.

HDPE is a high crystallinity, non – polar thermoplastic resin.High-density polyethylene (HDPE) is a kind of white powder granular product, non-toxic and tasteless, and its density ranges from 0.940 to 0.976 g/cm3.The crystallinity is 80%~90%, the softening point is 125~135℃, and the operating temperature is up to 100℃.The melting temperature is 120~160℃.It has good heat and cold resistance, good chemical stability, but also has higher rigidity and toughness, mechanical strength.Dielectric properties, environmental stress cracking resistance is also good.Hardness, tensile strength and creep property are better than low density polyethylene.Good wear resistance, electrical insulation, toughness and cold resistance. Good chemical stability, at room temperature, insoluble in any organic solvents, acid, alkali and various salts corrosion resistance.

Main Features:

The appearance of the original HDPE is milky white, in the thin section of a certain degree of translucent.PE has excellent resistance to most domestic and industrial chemicals.Certain types of chemicals produce chemical corrosion, such as corrosive oxidants (concentrated nitric acid), aromatic hydrocarbons (xylene), and halogenated hydrocarbons (carbon tetrachloride).The polymer is non – hygroscopic and has good water – proof vapor property and can be used for packaging purposes.HDPE has very good electrical performance, especially high dielectric strength of insulation, making it very suitable for wire and cable.Medium to high molecular weight classes offer excellent impact resistance at room temperature and even -40F low temperatures.Unique to each grade of HDPE is the appropriate combination of four basic variables: density, molecular weight, molecular weight distribution, and additive.Different catalysts are used to produce customized polymers with special properties.These variables combine to produce HDPE grades for different USES;Achieve the best balance in terms of performance.

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Production Process:

PE is the most common production method through slurry or gas additive method, there are a few with solution phase processing production.All these processes involve exothermic reactions involving ethylene monomers, A-alkene monomers, catalyst systems (which may be more than one compound), and various types of hydrocarbon diluents.Hydrogen and some catalysts are used to control the molecular weight.Slurry reactors are generally stirrer reactors or a more commonly used type of large annular reactor in which slurry can be cyclically stirred.Polyvinyl particles are formed when ethylene and comonomers (as needed) come into contact with the catalyst.After the diluent is removed, the polyethylene or powder particles are dried and the dosage of additives is added to produce the granule.Modern production lines for large scale reactors with twin screw extruders can produce more than 40000 pounds per hour.The development of new catalysts contributes to the improvement of the performance of the new grade HDPE.Two of the most commonly used catalyst types are Phillip’s chromium oxide-based catalyst and the titanium compound alkyl aluminum catalyst.The HDPE produced by Philips catalyst has medium width molecular weight distribution.The molecular weight distribution of titanium-alkyl aluminum catalyst is narrow.Catalysts used to produce narrow MDW polymers in a compound reactor can also be used to produce wide MDW grades.For example, two series reactors producing products with significantly different molecular weights can produce a bimodal molecular weight polymer with a full wide molecular weight distribution.


The addition of antioxidants can prevent the polymer from degrading during processing and prevent the oxidation of the finished product during use.Antistatic additives are used in many packaging grades to reduce the adhesion of bottles or packages to dust and dirt.Specific USES require special additive formulations, such as copper inhibitors associated with wire and cable USES.Excellent weather resistance and UV (or daylight) resistance can be achieved by adding anti-UV additives.No ANTI-UV or carbon black PE has been added. It is recommended not to use outdoors continuously.The high grade carbon black pigment provides excellent UV resistance and is often used in outdoor applications such as wire, cable, tank beds or pipes.

Processing Method:

PE can be manufactured by a wide range of different processing methods.With ethylene as the main raw material, propylene, 1-butene, hexene as the copolymer, under the action of catalyst, using slurry polymerization or gas polymerization process, the polymer obtained by flash evaporation, separation, drying, granulation and other procedures, to obtain uniform particles of the finished product.These include such products as sheet extrusion, film extrusion, pipe or profile extrusion, blow molding, injection molding, and roll molding.HDPE is suitable for all kinds of molding processes of thermoplastic molding, with good molding processing, such as injection molding, extrusion molding, blow molding, rotary molding, coating, foaming process, hot forming, hot sealing welding, hot welding and so on.

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Injection molded products: containers, caps, buckets, caps, food containers, dishes, trash cans, boxes, and plastic flowers.

Blow molding products: hollow molding products, such as various series of blow molding barrels, containers, bottles, containers for cleaning agents, chemicals, cosmetics, gasoline tanks, daily necessities, etc.There are also blown film products such as food packaging bags, grocery shopping bags, fertilizer lining film and so on.

Extruded products: pipes and fittings are mainly used in gas transportation, public water transportation and chemical transportation, such as building materials drain pipes, gas pipes, hot water pipes, etc. Sheet materials are mainly used for seats, suitcases, handling containers, etc.

Rotary molding: injection molding products such as large containers, storage tanks, barrels, boxes, etc.

Polyethylene granules can be processed into film, wire and cable sheath, pipe, all kinds of hollow products, injection products, fiber, etc.Widely used in agriculture, packaging, electrical and electronic, machinery, automobiles, daily necessities and other aspects.

IMRI supplies all kinds of PE and PP granules such as HDPE granules,MDPE granules,LDPE granules,LLDPE granules,HDPP granules,MDPP granules,LDPP granules,etc.Please contact us to get a quotation if you need any kind of them.