There are three main factors that restrict the development of iron and steel industry. The report released by Zhiyan Consulting website shows: First, the domestic real estate control policy will not be relaxed in the short term, and the growth rate of real estate sales and investment is declining; Second, the European debt crisis continued to plague the global economic operation, and the export growth rate of China slowed down obviously in 20 12; Third, the American economic recovery process is slow, which has limited pulling effect on the new round of world economic growth. In 20 12 years, China's steel industry is still facing enormous demand pressure. Reverse mechanism? Objectively, the industry itself is required to improve production efficiency, avoid homogenization competition and implement mergers and acquisitions to cope with the impact of the overall unfavorable environment. The growth rate of major downstream demand industries continued to slow down. Besides, why? Twelfth Five-Year Plan? With the vigorous implementation of planning and the acceleration of urbanization and infrastructure construction, China's economic development structure has begun to transform, and building a modern industrial system is the strategic focus.
Since the beginning of this year, the global economy has maintained a recovery trend, and the economic recovery momentum of developed countries, especially the United States and Britain, is strong. Relevant data show that the orders of durable consumer goods in the United States unexpectedly increased in April, the purchasing managers' index of manufacturing industry was 56.2 in early May, and the consumer confidence index rose in May, all indicating that the American economy is expanding at a faster speed. The initial comprehensive PMI of the euro zone in May was 53.9, slightly lower than the reading of 54 points in April, while the final value in April was the highest in the past three years (54.0). The index predicts that the economy will grow by 0.5% in the second quarter, which will be the strongest growth rate in three years.
Despite this, global economic growth is still fragile, dragged down by the weak economic growth of emerging economies. In order to consolidate economic recovery, developed countries will stick to or increase monetary easing in the second half of the year. The euro zone may announce another interest rate cut in June and implement a negative interest rate policy; The Bank of Japan said that if necessary, it will implement new? QE？ ; The minutes of the Fed's recent monetary policy meeting show that since the US inflation rate is expected to remain below the target level of 2%, the Fed will continue to take stimulus measures to reduce the unemployment rate. In other words, after the end of this year's bond purchase plan, its benchmark interest rate will remain at a very low level for some time.
In the second half of the year, the developed countries continued to implement the monetary easing policy, which stimulated the recovery of the real economy and became a new driving force for China's steel exports. According to the data of Zhiyan Consulting, in the first four months of this year, the country exported 25.87 million tons of steel, a year-on-year increase of 29.5%. Among them, the export in April was 7.54 million tons, a year-on-year increase of 36%.
Urbanization and industrialization continue to stimulate the demand for steel. 20 1 1 year, China's urbanization rate reaches 5 1.2%, which is still far from the standard of 70% in developed countries. The report points out that it is a good signal that the steel industry will continue to vigorously promote the urbanization process and vigorously improve the service level of urban infrastructure. China is still in the middle stage of industrialization. 20 1 1 year, the added value of China's tertiary industry reaches 43%, which is far from the reference standard of more than 50% in the later stage of industrialization. Judging from the current speed of industrialization in China, it will take at least 10 years to complete industrialization, during which steel consumption will continue to increase.
Per capita steel consumption continues to climb. At present, there is still a big gap between China's per capita steel consumption and that of developed countries. Take the United States as an example At the end of 1970s, the United States entered the late stage of industrialization, and the annual per capita steel consumption reached 7 1 1 kg, with an average annual increase of about 5%. In 2009, the per capita steel consumption in China was only 4 16 kg. If the average annual growth rate is 5%, it will still take about 12 years to reach the per capita steel consumption level of the United States in the 1970s.
The forecast figures show that the steel demand in China will show a slight growth trend in the next 5- 10 years. China steel industry? Twelfth Five-Year Plan? Planning forecast, China's crude steel demand may be in? Twelfth Five-Year Plan? During this period, it enters the peak arc top area, and the peak value may appear from 20 15 to 2020, with a peak value of about 770-820 million tons, an increase of 0.7-654.38+200 million tons compared with the current one.
The types of steel are distinguished according to the different carbon content.
Iron-carbon alloys are divided into steel and pig iron, and steel is an iron-carbon alloy with carbon content of 0.03% ~ 2%. Carbon steel is the most commonly used common steel, which is easy to smelt, easy to process and low in price, and can meet the use requirements in most cases, so it is widely used. According to the different carbon content, carbon steel is divided into low carbon steel, medium carbon steel and high carbon steel. With the increase of carbon content, the hardness of carbon steel increases and the toughness decreases. Alloy steel is also called special steel. Adding one or more alloying elements on the basis of carbon steel changes the structure and properties of steel, thus having some special properties, such as high hardness, high wear resistance, high toughness and corrosion resistance. The alloying elements often added in steel are silicon, tungsten, manganese, chromium, nickel, molybdenum, vanadium, titanium and so on. Alloy steel resources are quite rich, except for chromium and cobalt deficiency and low manganese grade, tungsten, molybdenum, vanadium, titanium and rare earth metals are in high reserves. At the beginning of 2 1 century, the proportion of alloy steel in the total steel output increased greatly.
Iron-carbon alloy with carbon content of 2% ~ 4.3% is called pig iron. Pig iron is hard and brittle, but it is resistant to compression and wear. According to the different forms of carbon in pig iron, it can be divided into white iron, gray iron and ductile iron. The carbon in white iron is distributed in the form of Fe3C, and the fracture is silvery white. It is hard and brittle, so it can't be machined. It is the raw material for steelmaking, so it is also called steelmaking pig iron. The fracture of gray cast iron with carbon distributed in flake graphite is silver gray, which is easy to cut, cast and wear-resistant. If carbon is distributed in spherical graphite, it is called ductile iron, and its mechanical properties and machinability are close to those of steel. Special cast iron can be obtained by adding special alloying elements to cast iron. If chromium is added, the wear resistance can be greatly improved, which has a very important application under special conditions.
Source of carbon in steel: One of the raw materials for ironmaking is iron ore, the main component is Fe2O3, and there is no carbon.
The second raw material for ironmaking is coke.
In the process of ironmaking, part of coke remains in molten iron, resulting in carbon in molten iron. Iron and steel are produced by smelting pig iron from iron ore.
Using pig iron as raw material for steelmaking, the process of steelmaking is mainly a process of carbon removal, and carbon cannot be completely removed. Steel needs a certain amount of carbon to achieve the best performance.
According to the chemical composition
1. carbon steel carbon steel refers to an iron-carbon alloy containing a small amount of elements such as manganese, silicon, sulfur and phosphorus in addition to iron and carbon. According to the different carbon content, it can be divided into:
(1) Low carbon steel-carbon content wc? 0.25%。
2 medium carbon steel-carbon content wc & gt0.25%~0.6 1%.
(3) high carbon steel-carbon content WC > 0.05；; 0.60% high carbon steel is generally used in military industry and industrial medical industry.
Second, alloy steel In order to improve the performance of steel, on the basis of smelting carbon steel, some alloying elements are added to steel, such as chromium steel, manganese steel, chromium manganese steel, chromium nickel steel and so on. According to the total content of alloy elements, it can be divided into:
(1) Low alloy steel-total content of alloying elements? 5%
(2) The total content of medium alloy steel-alloying elements is 5% ~ 10%.
(3) High alloy steel-total content of alloy elements > 10%.
Through smelting equipment
(1) converter steel converter-blown steel can be divided into bottom blowing, side blowing, top blowing, air blowing and pure oxygen blowing. According to the different lining, it can be divided into acidic and alkaline.
⑵ Open hearth steel The steel refined by open hearth furnace can be divided into acidic steel and alkaline steel according to the different lining materials. Generally, open hearth steel is mostly alkaline.
(3) Electric furnace steel The steel refined by electric furnace includes electric furnace steel, induction furnace steel and vacuum induction furnace steel. Alkaline EAF steel is produced in large quantities in industry.
According to the deoxidation degree before pouring
(1) Boiling steel belongs to steel with incomplete deoxidization, and the ingot mold appears boiling phenomenon during casting. Its advantages are less smelting loss, low cost, good surface quality and good deep drawing performance; The disadvantages are uneven composition and quality, poor corrosion resistance and mechanical strength, and it is generally used for rolling carbon structural steel profiles and plates.
⑵ Killed steel is a completely deoxidized steel. When pouring, the molten steel in the ingot mold is calm and has no boiling phenomenon. Its advantages are uniform composition and quality; Disadvantages are low metal output and high cost. General alloy steel and high-quality carbon structural steel are killed steel.
(3) Semi-killed steel, its deoxidation degree is between killed steel and boiling steel, because its output is difficult to control, and the output is not much.
According to the quality of steel
(1) Ordinary steel contains more impurity elements, but the sulfur content ws is average. O.05%, phosphorus content wP? 0.045%, such as carbon structural steel and low alloy structural steel.
(2) High-quality steel contains less impurity elements, and the contents of sulfur and phosphorus are generally equivalent to those of wp. 0.04%, such as high quality carbon structural steel, alloy structural steel, carbon tool steel and alloy tool steel, spring steel, bearing steel, etc.
(3) High-quality steel contains few impurity elements, and the sulfur content ws is average? O.03%, phosphorus content wP? 0.035%, such as alloy structural steel and tool steel. High-grade and high-quality steel is generally marked behind the steel number? Answer? Or Chinese characters? Tall? To prove identity.
Depending on the use of steel
I. Structural steel
(1) Structural steel for building and engineering is referred to as building steel for short, which refers to steel used for manufacturing metal structural parts in buildings, bridges, ships, boilers or other projects. Such as carbon structural steel, low alloy steel, strengthened steel, etc.
Structural steel for machinery manufacturing refers to the steel used for manufacturing structural parts on machinery and equipment. This kind of steel is basically high-quality steel or high-quality steel, mainly high-quality carbon structural steel, alloy structural steel, free-cutting structural steel, spring steel, rolling bearing steel and so on.
Second, the tool steel
Generally used for manufacturing various tools, such as carbon tool steel, alloy tool steel, high-speed tool steel, etc. According to the purpose, it can be divided into cutting tool steel, die steel and measuring tool steel
Three. special steel
Steel with special properties, such as stainless and acid-resistant steel, heat-resistant skinless steel, high-resistance alloy, wear-resistant steel, magnetic steel, etc.
Fourth, professional steel
This refers to the steel used in various industrial sectors, such as automobiles, agricultural machinery, aviation, chemical machinery, boilers, electricians and covered electrode.
Depending on the form of manufacturing and processing
(1) Cast steel Cast steel refers to a kind of steel castings produced by casting method. Cast steel is mainly used to manufacture some parts with complex shapes, which are difficult to forge or cut and require high strength and plasticity.
(2) Forged steel Forged steel refers to various forging materials and forgings produced by forging methods. The quality of forged steel parts is higher than that of cast steel parts, which can bear greater impact force, and the mechanical properties such as plasticity and toughness are also higher than that of cast steel parts, so forged steel parts should be used for all important machine parts.
(3) Hot rolled steel Hot rolled steel refers to all kinds of hot rolled steel produced by hot rolling method. Most steel products are hot rolled. Hot rolling is often used to produce large steel products such as section steel, steel pipe and steel plate, and also used to roll wire rods.
(4) Cold rolled steel Cold rolled steel refers to all kinds of cold rolled steel produced by cold rolling method. Compared with hot rolled steel, cold rolled steel is characterized by smooth surface, accurate size and good mechanical properties. Cold rolling is often used to roll sheet, steel strip and steel tube.
5] Cold-drawn steel bar Cold-drawn steel bar refers to all kinds of cold-drawn steel bars produced by cold-drawn method. Cold-drawn steel is characterized by high precision and good surface quality. Cold drawing is mainly used to produce steel wire, round steel and hexagonal steel with a diameter of less than 50 mm, and steel pipe with a diameter of less than 76 mm.
The common term of iron and steel is 1, and the standard is a unified regulation of repetitive things and concepts. It is based on the comprehensive achievements of science, technology and practical experience, approved by the competent department after consultation by all parties concerned, and published in a specific form as a guide and basis to follow. The standards of steel products in China include national standards (GB, GB/T), industrial standards (YB), local standards and enterprise standards.
2. The performance indicators and quality requirements specified in the technical conditions standards are called technical conditions, such as chemical composition, overall dimensions, surface quality, physical properties, mechanical properties, technological properties, internal organization and delivery status.
3, guarantee conditions According to the provisions of the technical conditions of metal materials, the manufacturer should conduct inspections to ensure that the inspection results meet the requirements of specified quality indicators such as performance, chemical composition and internal organization, which is called guarantee conditions.
4. Quality Certificate The production of metal materials, like the production of other industrial products, is carried out in accordance with unified standards, and the product ex-factory inspection system is implemented. Unqualified metal materials are not allowed to be delivered. For the delivered metal materials, the manufacturer shall provide quality certificates to ensure their quality. The quality certificate of metal materials not only indicates the name, specifications, number of delivered pieces, weight, etc. All inspection results of the specified guarantee items are also provided. The quality certificate is the supplier's confirmation and guarantee of the inspection results of this batch of products, and it is also the basis for the buyer's re-inspection and use.
5. Quality grades According to the allowable deviation requirements of steel surface quality, shape and size, the steel quality is divided into several grades. For example, first-class products, second-class products. Sometimes different grades are made for a certain requirement, such as the surface quality is divided into one, two and three grades, and the depth of decarburization layer on the surface is divided into one group and two groups, which all indicate the difference in quality.
6, accuracy grade Some metal materials have several allowable deviations in the standard. According to the size of the allowable deviation, they are divided into several grades, which are called accuracy grades. Accuracy grades are divided into general accuracy, higher accuracy and advanced accuracy according to allowable deviation. The higher the accuracy level, the smaller the allowable dimensional deviation. When ordering, attention should be paid to writing the accuracy grade requirements into the contract and other related documents.
7. The brand of brand metal material is the name of each specific metal material. The brand of steel is also called steel grade. The brands of metal materials in China can generally reflect the chemical composition. The brand number not only indicates the specific variety of metal materials, but also can roughly judge their quality according to it. In this way, the brand simply provides the same concept of the quality of a specific metal material, which brings great convenience to production, use and management.
8. Varieties of metallic materials refer to products with different uses, shapes, production processes, heat treatment states and particle sizes.
9. Model The model of metal material refers to the code names of products with different shapes and categories, such as profiles and cemented carbide, which are expressed by Chinese phonetic alphabet (or Latin) letters and one or several numbers. Numbers represent the nominal dimensions of major parts.
10, specifications refer to different sizes of the same variety or the same model of metal materials. Generally, the allowable deviation is different with different sizes. In product standards, the specifications of varieties are usually arranged in order from small to large.
1 1, and the surface state is mainly divided into two types: bright and unlit. Common in steel wire and steel strip standards, the main difference lies in bright annealing or ordinary annealing. There are also grinding, polishing, pickling, electroplating and so on as the surface state.
12. Edge state Edge state refers to whether the strip is trimmed. Trimming is trimming strip steel, and untrimmed strip steel is untrimmed strip steel.
13, delivery status Delivery status refers to the final plastic deformation processing or final heat treatment status of product delivery. Delivered products without heat treatment are hot-rolled (forged) and cold-rolled products. After normalizing, annealing, high-temperature tempering, quenching and tempering, solid solution and other treatments, it is collectively referred to as delivery in heat treatment state, or it is referred to as delivery in normalizing, annealing, high-temperature tempering and quenching and tempering state according to heat treatment categories.
14. The hardness of materials means that the hardness of steel is different with different degrees of heat treatment or work hardening. In some steel strip standards, it is divided into super soft steel strip, soft steel strip, semi-soft steel strip, low hard steel strip and hard steel strip.
The longitudinal and transverse steel standards mentioned in 15 refer to the relative relationship with the rolling (forging) and drawing directions, and those parallel to the machining direction are called longitudinal; Perpendicular to the machine direction is called transverse direction. Samples taken along the processing direction are called longitudinal samples; Samples perpendicular to the machine direction are called transverse samples. The fracture on the longitudinal specimen is perpendicular to the rolling direction, so it is called transverse fracture; The fracture on the transverse specimen is parallel to the machining direction, so it is called longitudinal fracture.
16, theoretical quality and actual quality These are two different methods to calculate the delivery quality. If the goods are delivered according to the theoretical quality, the delivery quality shall be calculated according to the nominal size and density of the materials. If delivered according to the actual quality, it is the delivery quality obtained by weighing (weighing) the materials.
17. Nominal dimensions and actual dimensions Nominal dimensions refer to the nominal dimensions specified in the standards, which are expected to be ideal dimensions in the production process. However, in actual production, the actual size of steel is often greater than or less than the nominal size, and the actual size is called the actual size.
18, deviation and tolerance Because it is difficult to reach the nominal size in actual production, there is an allowable difference between the actual size and the nominal size specified in the standard, which is called deviation. Negative difference is called negative deviation, and positive difference is called positive deviation. The sum of the absolute values of allowable positive and negative deviations specified in the standard is called tolerance. Deviation is directional, that is, with? Positive? Or? Negative? Indicates that the tolerance has no directionality.