Anti-corrosive steel pipe with internal epoxy coating and external polyethylene (PE) coating

Anti-corrosive steel pipe with internal epoxy coating and external polyethylene (PE) coating

Introduction:

Anti-corrosion steel pipes with internal epoxy coating and external polyethylene coating is a new type of steel-plastic composite pipe, which has excellent mechanical properties and anti-corrosion and anti-aging properties.Widely used in water conservancy, electric power, chemical industry, petroleum and many other industries.

Classification:

The anti-corrosive steel pipes with internal epoxy and external polyethylene coating is divided into: internal epoxy powder coating and external single layer PE coating steel pipe,internal  liquid epoxy coating and external single layer PE coating steel pipe, internal epoxy powder coating and external three layers PE coating steel pipe, internal liquid epoxy coating and external three -layer polyethylene coating steel pipe.

 

Inner epoxy coating external polyethylene coating structure composition:

  1. Steel pipesubstrate: seamless steel pipe, electric welded steel pipe(straight seam welded, spiral welded).
  2. Internal anti-corrosive coating: Sanitary grade fused epoxy powder coating, heavy anti-corrosive fused epoxy resin powder.
  3. External anti-corrosive coating: hot-melt single-layer polyethylene powder coating.

The internal epoxy coating external three-layer polyethylene (3PE) structure composition:

  1. Steel pipesubstrate: seamless steel pipe, electric welded steel pipe(straight seam welded, spiral welded).
  2. Internal anti-corrosive coating: Sanitary grade fused epoxy powder coating, heavy anti-corrosive fused epoxy resin powder.
  3. External anti-corrosion coating: hot-melt three-layer polyethylene coating, the bottom layer is fused epoxy resin powder, the middle layer is hot-melt adhesive, the outermost layer is high-density polyethylene.

Anti-corrosive steel pipe with internal epoxy coating and external polyethylene (PE) coating

Production process:

  1. Intermediate frequency heating steel pipe

Compared with the traditional electric furnace heating method, if heating has a higher conversion rate, which effectively saves the electric energy.Intermediate frequency heating is adopted, and the heat in the steel pipe is distributed from the inside to the outside, so that the heating temperature is more uniform, effectively ensuring the high quality curing of epoxy coating.

  1. Monolayer polyethylene adopts internal spray and external spray process

The technology of internal spraying epoxy powder and outer spraying polyethylene powder is called curtain method, also known as dappling process, which uses the waste heat of pipe to cure the two at the same time by means of intermediate frequency heating, and does not need to be separately coated and cured.

  1. The three-layer structure polyethylene usesthe fusion knot winding process

The internal wall is anti-corrosive coated by thermal spraying epoxy powder, and the powder is evenly coated on the internal surface of the steel pipe after high temperature heating and melting.The outer coating adopts high pressure extrusion winding technology, which greatly improves the compactness, toughness, abrasion resistance, impact resistance and bending resistance of the coating, and can effectively prevent the mechanical damage during construction and damage of plant roots and soil environmental stress in the process of use.

  1. Internal and external coatings of the steel pipes are done at the same time

Internal epoxy and external three layer PE realized synchronous coating, epoxy synchronous curing the core technology of one-time film, both inside and outside surface and spray coating not only greatly reduces the time, improve work efficiency, and coating process, the steel pipe under the internal and external coating packages at the same time, maximum reduces the heat loss, make full use of the latent heat of steel pipe, further improve the thermal efficiency.

 

Internal epoxy coating and external polyethylene coating pipeline characteristics:

1) The anti-fouling and anti-moth on the inner wall of the pipeline will not be attached by the fouling and anti-moth in the Marine or sewage microbial stations such as shell-shell and fungus.

2) Smooth inner coating, less fluid friction resistance than PCCP and ductile iron pipes.

3) The corrosion resistance of the inner wall of the pipe is better than that of ordinary PCCP and ductile iron pipe.

4) The single-layer polyethylene powder thermal spraying layer on the outer wall of the pipeline has strong soil corrosion resistance and environmental protection.

5) The pipe fittings with complete specifications can adapt to various installation needs.

6) The pipe can be connected by electric welding, clamp and flange.

7) Directly connected electric welding repair and repair method is simple and reliable.

8) The design life of internal and external anti-corrosive coating can reach more than 50 years.

 

Internal epoxy and external polyethylene anti-corrosive steel pipes are coated with corrosion resistance and deformation resistance.The outer coating is made of three-layer polyethylene with uniform coating thickness, which is closely combined with the steel pipe to improve the cathodic protection efficiency.The internal coating adopts thermosetting epoxy, the coating is hygienic and safe, and has no influence on the water quality. It can not only be used in the city supply and drainage pipe network and the long-distance transportation pipeline of tap water, sewage, medium water and sea water of various water quality, but also can be used as the transportation pipeline of oil, gas and mixed medium of oil and gas.And epoxy and polyethylene anti-corrosive steel pipe comprehensive cost is low, is in line with the green, environmental protection, low carbon, energy saving excellent products.With our more than ten years’ experience in pipe coating field,IMRI will surely provide you anti-corrosion coating steel pipes which can meet your needs.

What are differences between steel pipe of API 5L PSL1 and PSL2 ?

What are differences between API 5L PSL1 and PSL2 steel pipe ?

What are differences between API 5L PSL1 and PSL2 steel pipe ?

API 5L generally refers to the implementation standard of steel line pipe, which is used to transport oil, gas and water extracted from the ground to oil and natural gas industry enterprises.

steel line pipe includes seamless steel tube and welded steel tube. Currently, welded steel tube types commonly used on pipelines in China include spiral submerged arc welding tube (SSAW), straight seam submerged arc welding tube (LSAW) and resistance welding tube (ERW). Seamless steel tube is generally used when the diameter of pipeline is less than 152mm.

Raw material of API 5L steel tube has many kinds of steel grades, such as GR.B, X42, X46, X52, X56, X60, X70, X80, etc. Now large steel mills have developed pipeline steel tube with steel grades of X100 and X120. The higher the requirements for raw materials and production, the higher the steel grade is, and the carbon equivalent between different steel grades is strictly controlled.

When it comes to API 5L, we all know that there are two standards below it, PSL1 and PSL2. Although the difference is only one word, the contents of these two standards are quite different. This is like GB/T9711.1.2.3 standard almost, all say the same, the requirement is a thousand miles apart.

Let me elaborate on the differences between PSL1 and PSL2:

PSL is short for product specification level. The product specification level of pipeline pipe can be divided into PSL1 and PSL2, which can also be said that the quality level can be divided into PSL1 and PSL2.

PSL2 is higher than PSL1, and these two specifications have different requirements not only for inspection, but also for chemical composition, mechanical properties and tolerance. Therefore, when placing an order according to API 5L, in addition to the usual indicators such as specification and steel grade, the contract must also indicate the product specification level, namely, PSL1 or PSL2.

PSL2 is superior to PSL1 in chemical composition, tensile property, impact work, nondestructive testing and other indexes.

1. Chemical composition

API 5L PSL1 chemical compositionAPI 5L PSL2 chemical composition

2. Mechanical Properties

PSL1 does not require impact performance. For all steel grades of PSL2 except X80, the average value of Akv at 0℃ at full size: longitudinal ≥41J, transverse ≥27J, at the same condition for X80: longitudinal ≥101J, transverse ≥68J


PSL2 mechanical properties

3. Tolerance

Tolerance of PSL2 pipe size
tolerance of PSL1 wal thickness tolerance of PSL2 wall thickness

4. Inspection and Defect Repair

Non-destructive inspection of a seamless pipe is mandatory for PSL2 pipe whereas for PLS1 pipe it is supplementary requirements. Repair of pipe body plate and skim by welding is not allowed in PSL2 pipes whereas it is allowed in PSL1 pipes. Similarly, weld repair without filler metal is not allowed in PSL2 pipes whereas it is allowed with purchaser’s permission in PSL1 pipes.

Baotou Steel is the top 3 manufacturer and supplier of seamless steel line pipe in China. It has the world’s most advanced production equipment PQF mill. It can fabricate GR.B, X42, X46, X52, X56, X60, X70, X80 with 1.8 million tons annual output of seamless steel pipe. If you want to learn more, please feel free to contact me.

Functions of 325 mesh 1250 mesh 4000 mesh calcined kaolin used in paint,ceramic,rubber and papermaking industry

Functions of 325 mesh 1250 mesh 4000 mesh calcined kaolin used in paint,ceramic,rubber and papermaking industry

Definition:

Kaolin is a mixture of inorganic nonmetals. Calcination of kaolin means that kaolin is sintered in a calcining furnace to a certain temperature and time, so that its physical and chemical properties can be changed to meet certain requirements.

 

Calcined kaolin is produced by ultrafine grinding and calcination modification with advanced  equipment.The product has a pseudo-hexagonal porous and lamellar structure, and the porosity is about 75%.The porous and lamellar structure of kaolin has the advantages of plasticity, adhesion, dispersion, insulation, sintering, flame retardancy, fire resistance, adsorption, weathering resistance, chemical stability, high light scattering rate, good hiding power and so on.Widely used in papermaking, coating, papermaking filler, plastic, rubber, wire and cable, latex paint, road sign paint, powder coating and other fields.

Functions of 325 mesh 1250 mesh 4000 mesh calcined kaolin used in paint,ceramic,rubber and papermaking industry

Function of calcined kaolin in paints and coatings:

Calcined kaolin raw ore is mainly produced in the coal producing areas of North China, mainly Inner Mongolia and Shanxi. It belongs to sedimentary type. It is formed by grinding hard kaolin generated from coal seam for many times and calcining at high temperature. After such processing, calcined kaolin molecules lose crystal water and present fluffy porous sheet structure. Calcined kaolin has the characteristics of high whiteness, strong covering power, good fluidity, high oil absorption and good suspension. The properties of coatings and films obtained by adding this kind of fine calcined kaolin in latex paint will make us feel that kaolin is not only a common filler, but also a functional filler to improve the quality of paints and coatings.Calcined kaolin used in paints and coatings has the following advantages:

  1. Due to its hexagonal crystal structure and high refractive index, it greatly improves the contrast index (covering power) of the coating film and provides excellent color ductility.
  2. The flat property of kaolin can provide a good balance between the fluidity and leveling of paints and coatings. Flat particles also tend to have a flat surface.For sticky film, flat particles can improve the compressive adhesion of the paints and coatings.
  3. Kaolin is hydrophilic, so it is easy to disperse, with small bulk density and good suspension performance.
  4. It has a narrow range of colloidal particles, tends to keep the viscosity of the coating unchanged, and can provide the required rheological properties and contactdenaturation (high shear high flow and low shear low flow), so the film is relatively full, and can improve the floating color and the defects of the flower.
  5. Strong chemical inertness, small optical axis angle and high order of crystal shape will significantly increase the UV shielding ability of the paints and coatings.

Function of calcined kaolin in ceramics and glazes:

The function of kaolin in glazes is to form vitreous material.The ideal chemical formula of kaolin is Al2O3-2SiO2-2H2O, which, like quartz, feldspar, marble, etc., is the main component of forming glass.

Kaolin is mainly composed of Al2O3 and a small amount of silicon dioxide.Alumina content is more, can improve the viscosity of the glaze, so that the glaze fixed in the bad body is not easy to flow away, but relatively will also increase the firing temperature of the glaze, and will affect the diffusion of the glaze, so that the crystallization is more difficult to produce.

 

Function of calcined kaolin in paper industry:

Pure kaolin has high whiteness, soft quality, easy dispersion and suspension in water, good plasticity, high adhesion, and excellent electrical insulation performance.It has good acid solubility, low cation exchange capacity, good fire resistance and other physical and chemical properties.Therefore, kaolin has become a necessary mineral raw material for dozens of industries such as papermaking, ceramics, rubber, chemical, coating, medicine and national defense.Kaolin is widely used in paper industry.

There are two main areas, one is in the paper in the use of fillers, the other is in the surface coating process used pigments.Especially in recent years, the rapid development of modern science and technology has made the application of kaolin more extensive. Some high-tech fields begin to use kaolin as a new material in large quantities. Even the high-temperature resistant porcelain parts of atomic reactors, space shuttles and spacecraft are also made of kaolin.

The paper industry is the largest consumer of refined kaolin, accounting for about 60% of total kaolin consumption.

 

Application of kaolin in rubber industry:

Kaolin used in rubber industry is made of high-quality raw materials by washing and refining. The product has fine particle size, low moisture, stable PH and DPG absorbency, and the settlement volume is higher than the index stipulated by the Chemical Industry Department.All kinds of rubber products produced by this product have low abrasion, good strength and bending performance.The product is a semi-strong filler for the production of various rubber products.

Differences between calcined kaolin and washed kaolin:

First of all, calcined kaolin is calcined, and its crystal form and original soil have changed.Water – washed kaolin is only treated physically and will not change the nature of the original soil.

Secondly, the whiteness of kaolin varies greatly. Generally, after light burning, the whiteness of kaolin will increase, while that of washing will not increase significantly.

Third, different USES.According to different calcination temperature, kaolin can be used as papermaking additive and refractory aggregate.

Washable kaolin is commonly used as a papermaking filler.

In addition, calcined kaolin mainly refers to hard kaolin (coal measure kaolin). The original soil has no bonding property and cannot be directly used as raw material for papermaking or refractory materials, so it needs to be applied after calcination.The raw material of washable kaolin has adhesive property and can be used as refractory binder or papermaking filler directly.It can improve the aging-resistant ability of the film, prolong its service life, improve its heat preservation and promote the growth of crops.Changing the polarity of the film surface and inhibiting the formation of fog drops;And will be harmful to the crops ultraviolet light or green light into photosynthesis can use red orange light, referred to as longevity, high heat preservation, anti-fog drops and light four functions, is a new master with functional filler.

As a papermaking filler, calcined kaolin has a better whiteness and a higher cost.

 

Inner Mongolia Rational Industry Limited (IMRI) is a supplier of all kinds of high whiteness calcined kaolin clay such as 6250 mesh calcined kaolin,325 mesh calcined kaolin,2000 mesh calcined kaolin,1250 mesh calcined kaolin,4000 mesh calcined kaolin,etc.Please send your inquiry and get quotation from us if you need any kind of calcined kaolin.

 

 

 

 

Why is EVOH the highest barrier material ?

Why is EVOH the highest barrier material ?

Why is EVOH the highest barrier material ?

Ethylene Vinyl Alcohol, commonly abbreviated EVOH, is a formal copolymer of ethylene and vinyl alcohol.

EVOH has always been used as high barrier material. The film types of this material in addition to non-tensile type, there are bidirectional tensile type, aluminum evaporation type, and adhesive coating type, etc., bidirectional tensile type and heat resistant type for aseptic packaging products. EVOH is characterized by excellent barrier property for gas and excellent processing property, and excellent transparency, gloss, mechanical strength, elasticity, abrasion resistance, cold resistance and surface strength.

(1) Chemical Properties

Polyvinyl alcohol (PVA) has the lowest gas permeability of any polymer available today. However, PVA is water-soluble and difficult to process.

EVOH preparation method: first, ethylene and vinyl acetate copolymer were copolymerized, and then the copolymer was hydrolyzed to obtain ethylene – vinyl alcohol. Therefore, it still retained the high barrier function, but in the moistureproof and the processing performance aspect has the obvious improvement.

In terms of properties, EVOH copolymer is highly crystalline, and its properties mainly depend on the relative concentration of its comonomer. Generally speaking, when ethylene content increases, gas barrier property decreases, moisture resistance improves, and resin is easier to process. The most prominent feature of EVOH resin is its barrier to gases. It is used in packaging structures to improve retention of fragrance and quality by preventing oxygen infiltration. In the use of gas-filled packaging, EVOH resin effectively retains the carbon dioxide or nitrogen used to protect the product.

Due to the presence of hydroxyl groups in the molecular structure of EVOH resin, EVOH resin is hydrophilic and hygroscopic. When adsorbing moisture, the barrier property of gas will be affected. However, the moisture content in the barrier layer can be carefully controlled, which can be achieved by wrapping EVOH resin layers in a multi-layer technique using strong barrier resins such as polyolefin.

 

(2) Oil Resistance

EVOH resin also has strong resistance to oil and organic solvents. After immersion in various solvents and oils at 68°F for 1 year, the percentage weight gain was 0% for solvents such as p-cyclohexane, xylene, petroleum ether, benzene, and acetone, 2.3% for ethylene glycol, 12.2% for methanol, and 0.1% for salad oil.

 

(3) Thermal/mechanical Properties

EVOH resin has high mechanical strength, elasticity, surface hardness, wear resistance and weather resistance, and has a strong antistatic property.

EVOH films are highly transparent due to their high gloss and low haze.

EVOH resin is the highest thermal stability resin among all commercial strong barrier resins. This property enables the processing of waste products can be recycled and reused, the raw materials contain up to 20% of EVOH.

 

(4) Processing

There are three basic ways to provide compartments using EVOH in a multilayered structure. They are:

  1. Coextrusion structure: EVOH resin binds to polyolefin or polyphenolamine to form a framework.
  2. EVOH films are laminated to other substrates or coated with other materials.
  3. Resin is used as coating for various substrates or single-layer containers.

It can be easily processed on traditional manufacturing equipment without special changes.

Using commercial equipment, EVOH resin is suitable for the following processing: single or multi-layer thin film extrusion; Sheet and profile co-extruded; Co-extrusion blow molding; Coextruded coating; Lamination (or lamination) and injection molding.

Secondary processing such as heat forming, vacuum forming and printing of EVOH resin frames or EVOH films is easy. Like other polymers, EVOH resins can be modified by overheating.

Coating techniques including multilayer coatings or coextruded coatings can also be used to produce multilayer structures, resulting in structures very similar to coextruded structures.

EVOH resin can be used for spraying, immersion or roller coating methods. The production of carbonated beverage containers or to achieve the purpose of blocking solvents, spices or smell.

EVOH resins have poor adhesion to most polymers, and to overcome this difficulty a specially designed bonding resin or “bonding resin” is required. Except for nylon, EVOH resin can stick to nylon well without the use of adhesive resin.

 

(5) New development

With the increase of rigid and high barrier plastic packaging, new performance requirements for EVOH resin are put forward. To meet these requirements EVOH suppliers offer certain brands such as J102(EVAL -EVALCA, USA) and Goshei, Japan’s ST series. These products improve machinability and a wider range of molding. Other products, such as EVAL inc. ‘s F100 and E151, have been developed for better viscosity and better match the polyolefin typically used in rigid containers.

At the same time of accelerating the research of EVOH composite film, the tensile orientation of EVOH is also being studied abroad. The barrier property of the new EVOH film to gas is 3 times that of the existing high performance non-tensile EVOH film.

In addition, EVOH can also be used as a barrier material coated on other synthetic resin packaging materials to enhance the barrier performance.

 

(6) Applications

  1. Non-food applications include solvents, chemicals, air conditioner components, gasoline drum lining, electronic components, and packaging of medically related products.
  2. In the field of packaging, EVOH is made into a composite film as a intermediate barrier layer, which is used in all hard and soft packaging. In the food industry for aseptic packaging, hot cans and cooking bags, packaging dairy products, meat, canned fruit juices and condiments; Plastic containers of EVOH can completely replace glass and metal containersIn terms of food packaging. Many domestic aquatic products companies export seafood using five layers of PE/EVOH/PA/EVOH/PE co-extrusion membrane vacuum packaging.
  3. EVOH products can not only be used in film production, but also can be widely used in soft packaging of cosmetics, floor heating pipes, jelly cups and pesticide bottles, etc. As a non-toxic and environmentally friendly material, EVOH can not only improve people’s life quality, but also play an important role in environmental protection.

 

EVOH is currently produced by Changchun Group of Taiwan province, Synthetic Chemistry of Japan and KURARAY of Japan. Our company can supply you all grades of EVOH with high quality and competitive price. Sample is available, if you have any need, please feel free to contact me anytime.

What’s the usage of seamless steel pipes

What’s the usage of seamless steel pipes?

Seamless steel tubes have hollow sections and are widely used as pipelines for conveying fluids, such as pipelines for conveying petroleum, natural gas, gas, water and some solid materials.Steel tubes can be divided into round tubes and special-shaped tubes according to the shape of cross-sectional area.Since a circle has the largest area with the same circumference, more fluid can be transported in a circular tube.In addition, when the annular section bears internal or external radial pressure, the force is more uniform, so most steel tubes are round tubes.

However, the circular pipe also has certain limitations, such as under the condition of plane bending, the circular pipe is not as strong as square, rectangular pipe bending strength, some agricultural machinery framework, steel and wood furniture, etc., are commonly used square, rectangular pipe.Other special-shaped steel tubes with different section shapes are required according to different USES.

What’s the usage of seamless steel pipes?

Seamless steel pipes of different usage:

1.Seamless steel tubes for construction

Standards: GB/T8162, ASTM A501, JIS G344,ASTM A500

Common grades: 10#, 20#, 35#, 45#, 40Mn2, 45Mn2, 27SiMn, 20Cr, 40Cr, 20CrMo, 35CrMo, 38CrMoA1, 50CrV, 30CrMnSi

 

2.Seamless steel tubes for conveying fluids

Standard: GB/T8163,ASTM A53, ASTM A192, JIS G3452, DIN 1629

Commonly used steel grades: 10#, 20#, Q295, Q345

 

3.Line pipes and petroleum seamless steel casing & tubing

Standard: API 5CT,API 5L

Common grades: J55,K55,L80, N80,P110,grade B, X42,X46,X52,X56,X60,X65,X70

 

4.Seamless steel tubes for gas cylinders

Standard:GB 18248,EN 10297,EN 10083,JIS G3429

Commonly used steel grades:34Mn2V, 30CrMo, 35CrMo,37Mn,34CrMo4,30CrMoSiA,38Mn6,30CrMo4,42CrMo4

 

5.Seamless steel tubes for high pressure boilers

Standard: GB5310,ASTM A106, ASTM A210C, ATSM A213, JIS G3461, JIS G3462, DIN 17175,BS3059: Part 2

Common steel grades: 20G, 20MnG, 25MnG, 15MoG, 20MoG, 12Cr1MoVG, 15CrMoVG, 12Cr2MoG, 12Cr2MoWVTiB, 12Cr3Movsib

 

6.Seamless steel tubes for low and medium pressure boilers

Standard: GB3087,ASTM A179, ASTM A192

Common brands: 10#, 20 #

 

7.High pressure seamless steel tubes for fertilizer equipment

Standard: GB6479,ISO 9329-2

Common steel grades: 10#, 20G, Q345, Q390, 10MoVNb, 12CrMo, 15CrMo, 12Cr2Mo

 

8.Petroleum cracking seamless steel pipe

Standard: GB/T9948, JIS G3441

Common brands: 10#, 20#, 12CrMo, 15CrMo, 1Cr2Mo, 1Cr5Mo

 

9.Seamless steel pipe for car half axle sleeve

Standard: Q/OHAD001 YB/T5035,DIN 1629

Common steel grades: 45Mn2, 45#, 25MnCr

 

10.Hot rolled seamless steel tubes for hydraulic props

Standard: Q/OHAD010  GB/T17398

Common steel grade: 27SiMn

 

11.Seamless steel pipe for ship

Standard: GB/T5312,DIN 2391

Commonly used brands: Q320, Q360, Q410, Q460 and Q490

 

12.Cold drawn precision seamless steel tube

Standard: GB/T3639, GB/T8713

Common steel grades: 10#, 20#, 35#, 45#, 30CrMo

 

13.Seamless steel pipe for geological drilling

Standard: YB/T5052,YB235

Commonly used steel grades: DZ40, DZ50

 

Seamless steel tube is a kind of economic section steel, has a very important position in the national economy, widely used in petroleum, chemical industry, boiler, power station, ship, machinery manufacturing, automobile, aviation, aerospace, energy, geology, construction and military sectors.IMRI supplies seamless steel pipes of all kinds of usages.Just tell us your requirements and you will get seamless steel pipes which meet your needs from us.

 

 

 

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(C):

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.

 

Silicon(Si):

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.

 

Manganese(Mn):

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.

 

Phosphorus(P):

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.

 

Sulfur(S):

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(N):

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(H):

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.