Steel bars are divided according to their chemical composition, what is the composition of reinforce

In engineering, it is usually classified according to chemical composition, which is divided into carbon steel, low-alloy steel, and alloy steel.

Indication of steel product grade: Chinese pinyin + chemical symbol + Arabic numerals.

The carbon structural steel grade contains information: the letter Q indicating the yield point, the yield point grade, the quality grade, and the degree of deoxidation. Determined according to GB T700-1988.

There are five types of yield point values: Q195, Q215, Q235, Q255, Q275; Expressed as a yield point of 235n mm2. Such as: Q235-A b C

Quality grade: refers to the amount of sulfur and phosphorus impurities. There are four grades: A, B, C, and D.

High-quality carbon steel (implementation standard GB T699-1999) grade: expressed in two digits, representing the percentage of carbon content. Such as: 20

Low-alloy high-strength alloy steel grade representation method: yield point grade + quality grade.

Yield point grades: Q295, Q345, Q390, Q420, Q460

Quality grades: e, d, c, b, a

There are several regulations on the representation of alloy structural steel grades:

Alloy structural steel and spring steel: a two-digit representation of the average carbon content of several parts per thousand;

Stainless acid-resistant steel, heat-resistant steel: the average carbon content is expressed in thousands; When the average C content is 0, it is represented by 0 (low carbon); c, it is represented by 00 (ultra-low carbon); When the content of C is 1%, the content of C is not labeled;

When the average alloy content is average, only the elements are marked in the grade, and the alloy content is not marked;

The average alloy content is 2, 3 ......

According to the chemical composition, steel can be divided into two categories: carbon steel and alloy steel.

Concrete is a mixture of cement (usually Portland cement) with aggregates.

The reason why reinforced concrete can work together is determined by its own material properties. First of all, steel and concrete have approximately the same linear expansion coefficient, and will not be overstressed due to different environments. Secondly, there is a good adhesion between the steel bar and the concrete, and sometimes the surface of the steel bar is also processed into spaced ribs (called deformed steel bars) to improve the mechanical occlusion between the concrete and the steel bar.

When this is still not enough to transmit the tensile force between the rebar and the concrete, the ends of the rebar are usually bent up 90 degrees. In addition, the alkaline environment provided by calcium hydroxide in concrete forms a passivation protective film on the surface of the steel bar, making the steel bar less susceptible to corrosion than in neutral and acidic environments.

Advantages and disadvantages of reinforced concrete:

Advantages: 1. The reinforced concrete structure can be made of local materials;

2. The durability of reinforced concrete is relatively good;

3. The integrity and grindability of the reinforced concrete structure are relatively good;

4. Reinforced concrete is more economical than steel structure.

Disadvantages: 1. The self-weight of the reinforced concrete structure is relatively large;

2. Reinforced concrete is more labor-intensive, and it is very expensive to formwork.

The so-called reinforced concrete is steel and concrete, which is composed of cement, sand, coarse aggregate (pebbles, stones, etc.) and water.

Reinforced concrete actually means that concrete is poured on a structure with steel bars, and in the final analysis, it is still concrete. It's nothing more than cement, sand, stone, and water. There are also fly ash, mineral powder, admixtures and so on.

Reinforced concrete has higher requirements than plain concrete. There is an electric flux requirement in the water transportation project, the chloride ion content of the mixture (reinforced concrete); chloride ion content of plain concrete) mixture; Prestressed concrete) chloride ion content of the mixture. There is also a protective layer requirement for reinforced concrete structures.

You can check the specifications for details.

Reinforced concrete materials: cement, water, stone, sand, admixtures (add when needed), according to different needs, can be made into concrete of different specifications, and then poured such as the made steel model, the formation of the required steel products.

Reinforced concrete has higher requirements than plain concrete. There is an electric flux requirement in the water transportation project, the chloride ion content of the mixture (reinforced concrete); chloride ion content of plain concrete) mixture; Prestressed concrete) chloride ion content of the mixture. There is also a protective layer requirement for reinforced concrete structures.

I don't know what you mean by that? Rebar? What is the diameter of the rebar? Cement? What is the number of cement? Or what?

The reinforcement arranged in the reinforced concrete structure can be divided into the following types according to its function:

1. Stressed ribs: steel bars that bear tensile and compressive stress.

2. Stirrups: bear a part of the diagonal tensile stress and fix the position of the stress bars, which are mostly used in beams and columns.

3. Erection bar: It is used to fix the position of the steel hoop in the beam and form the steel skeleton in the beam.

4. Distributed ribs: used in roof panels and floor slabs, arranged perpendicular to the stressed ribs of the slab, the weight of the bearing is evenly transmitted to the stressed ribs, and the position of the stressed ribs is fixed, as well as the temperature deformation caused by thermal expansion and contraction.

The process performance of performance steel bar includes many items, and different requirements can be put forward according to the characteristics of different products, such as bending and reverse bending (reverse bending) tests for ordinary steel bars, and repeated bending, torsion, and winding tests for some prestressed steels.

The form of all these tests simulates the process processing methods that may be involved in the actual use of the material to varying degrees, such as the ordinary steel bar needs to be hooked or bent to form, and the prestressed steel wire sometimes needs to be wound, etc., and its purpose is to assess the ultimate bearing capacity of the material to these specific plastic deformations, so the process performance is also the plastic requirement of the material, and it is common with the above-mentioned ductility requirements, generally speaking, the steel with large elongation has good process performance.

In addition to the main chemical component iron (Fe), the steel bar also contains a small amount of carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), oxygen (0), nitrogen (N), titanium (yang, alum ( ) and other elements. (1) Carbon is an important element that determines the performance of steel bars, and it has a great impact on the mechanical properties of steel. When the carbon content in the steel is below, with the increase of carbon content, the strength and hardness of the steel increase, and the plasticity and toughness decrease.

For steels with greater carbon content, their weldability will be significantly reduced. (2) Silicon is a beneficial element in steel, and it plays a role in deoxidation in steelmaking. It is the main alloying element of steel in China, and its role is mainly to improve the mechanical strength of steel.

3) Manganese is a beneficial element in steel, which can play a role in deoxidation and desulfurization in steelmaking, which can reduce the thermal brittleness caused by sulfur, improve the hot working properties of steel, and improve the strength and hardness of steel. (4) Phosphorus is one of the most harmful elements in steel. With the increase of phosphorus content, the strength and hardness of the steel are improved, and the plasticity and toughness are significantly reduced, especially the lower the temperature, the greater the impact on the plasticity and toughness, thereby significantly increasing the cold brittleness of the steel.

Phosphorus significantly reduces the weldability of steel, but improves the wear and corrosion resistance of steel. Construction steel generally requires a phosphorus content of less than 0. 045%。

5) Sulfur is a very harmful element, which can reduce various mechanical properties of steel. Sulfur reduces the weldability, impact toughness, fatigue resistance and corrosion resistance of steel. Construction steel generally requires that the sulfur content should be less than.

6) Oxygen is a harmful element in steel, which can reduce the mechanical properties of steel, especially toughness. Oxygen has the effect of promoting aging tendency. The low melting point caused by the oxide also makes the weldability of the steel worse.

It is usually required that the oxygen content in the steel is less than. (7) The effect of nitrogen on steel is similar to that of phosphorus and sulfur, which increases the strength of steel and significantly decreases plasticity, especially toughness, which will aggravate the aging sensitivity and cold brittleness of steel and reduce weldability. It is usually required that the nitrogen content in the steel is less than.

8) Titanium is a strong deoxidizer, which can significantly increase strength and improve toughness, but slightly reduce plasticity. Titanium reduces aging tendencies and improves weldability. (9) Vanadium is a weak deoxidizer, which can weaken the adverse effects of carbon and oxygen when added to steel, which can effectively improve the strength and reduce the sensitivity of efficiency, but has a tendency to increase hardening during welding.

Master Project:

1.When the steel bar enters the site, the specimen should be extracted in accordance with the provisions of the current national standard "hot-rolled ribbed steel bar for reinforced concrete" GB1499 as a performance test, and its quality must meet the provisions of the relevant standards.

Inspection quantity: determined according to the sampling inspection plan of the batch and product entering the site.

Inspection method: check the product certificate, factory inspection report and entry re-inspection report.

2.For frame structures with seismic fortification requirements, the strength of the longitudinal stressed steel bars should meet the design requirements; When there are no specific requirements for the design, yes.

For the first and second level seismic grades, the measured value of the strength obtained from the inspection shall comply with the following provisions:

1) The ratio of the measured tensile strength of the steel bar to the value should not be less than;

2) The ratio of the measured yield strength of the steel bar to the strength standard value should not be greater than.

Inspection quantity: determined according to the sampling inspection plan of the batch and product entering the site.

Inspection method: check the re-inspection report.

3.When it is found that the steel bar is brittle, the welding performance is poor or the mechanical properties are significantly abnormal, the chemical composition of the batch of steel bars should be tested or other special inspections.

Inspection method: check the chemical composition and other special inspection reports.

The above content is from the Code for Acceptance of Construction Quality of Concrete Structure Engineering GB 50204-2002 I hope it will be helpful to you.

If one of the following conditions occurs in the steel bar, the chemical composition test must be done:

1) There is no factory certificate or the steel grade and steel number are unknown;

2) Imported steel bars with welding requirements;

3) In the process of processing, brittleness, poor welding performance and significant abnormal mechanical properties occur.

Analysis of the chemical composition of steel.

The analysis of chemical products using steel includes wet analysis and spectral analysis, as follows: the main test items of wet analysis of steel: C, S, P, MN, SI, CR, NI, CU, MO, V, TI, AL, MG, NB, B, CEQ and PCM;

Spectral analysis of carbon steels and low- and medium-alloy steels: C, S, P, MN, SI, CR, NI, CU, MO, V, TI, AL, W, NB, B; Stainless steel: C, S, P, MN, SI, CR, NI, CU, MO, TI, AL, W.

If the steel bar has one of the following conditions, the chemical composition must be tested: (1) there is no factory certificate or the steel number of the steel is unknown; 2) Imported steel bars with welding requirements; 3) In the process of processing, brittleness, poor welding performance and significant abnormal mechanical properties occur.

When the hot-rolled steel bar is brittle, the welding performance is poor or the mechanical properties are significantly abnormal during the processing process, chemical composition analysis and other special inspections should be carried out.

The inspection of the steel bar should first check the brand number and quality certificate of the steel bar; Secondly, the appearance inspection should be done, 5% of the steel bar should be extracted from each batch, and the surface of the steel bar should not be cracked, wounded and stacked, and the bump on the surface of the steel bar should not exceed the height of the cross rib, and the depth and height of the defect should not be greater than the allowable and deviation of the part.

The bending of the steel bar should not be greater than four millimeters per meter; Next, if each batch is less than 60 tons, 2 will be extracted from it, and two sections of each will be intercepted for tensile and cold bending tests respectively.

100 500mm at both ends of the steel bar should be removed when the specimen is intercepted, and the corresponding steel bar should be taken when the specimen is more than 60 tons. If the results of one test do not meet the requirements, double the number of samples from the same batch is taken for each test.

Chemical composition testing must also be done in one of the following cases:

1. Imported steel bars;

2. In the process of processing, brittleness, poor welding performance and significantly abnormal mechanical properties occur;

3. If there are special requirements, the corresponding special test should also be carried out;

4. For the steel bars that are centrally processed in the factory and the construction site, the factory certificate issued by the processing unit and the copy of the steel bar factory certificate and the steel bar test report shall be issued;

5. When welding steel bars produced in different grades and different countries, there should be a weldability test report.

When the steel bar raw material has brittle breakage, poor welding performance or abnormal mechanical properties, the chemical composition of the batch of steel bar raw materials should be tested or other special inspections.

Hello, the main component of steel is iron and other metal substances, the ratio of iron to other metal substances determines the hardness, plasticity and strength of steel and other properties, if the customer is more professional in this area, you may be asked to test the content of each metal substance in the steel, in order to grasp the product quality.

According to the requirements, the imported steel bars need to be tested for chemical composition.