Technical parameters

Numbering and representation of steel
① The chemical composition is represented by the international symbol of chemical elements and the symbol of the country, and the composition content is represented by the Arabic alphabet:
For example: China, Russia 12CrNi3
(2) Use fixed digit numbers to indicate steel series or numbers; Such as: the United States, Japan, 300, 400, 200 systems;
③ Use the Latin alphabet and the order to form the serial number, only to indicate the purpose.
China’s numbering rules
① Use element symbols
② Application, Chinese Pinyin, open hearth steel: P, boiling steel: F, calm steel: B, Class A steel: A, T8: special 8, GCr15: ball
◆ Alloy steel, spring steel, such as 20CrMnTi 60SiMn, (with a few parts of the C content)
◆ Stainless steel, alloy tool steel (with a few thousandths of C content), such as: 1Cr18Ni91/000C (0.1%C), stainless C≤0.08% such as 0Cr18Ni9, ultra-low carbon C≤0.03% such as 00Cr17Ni13Mo
International method for marking stainless steel
The American Iron and Steel Institute uses a three-digit number to label standard grades of malleable stainless steel. Among them:
① Austenitic stainless steels are marked with 200 and 300 series numbers. For example, some more common austenitic stainless steels are marked with 201, 304, 316 and 310.
② Ferrite and martensitic stainless steel are represented by 400 series numbers.
③ Ferritic stainless steel is marked with 430 and 446, martensitic stainless steel is marked with 410, 420 and 440C.
(4) duplex (austenitic – ferrite), stainless steel, precipitate-hardened stainless steel and iron content of less than 50% of the high alloy is usually named by patent or trademark.
4). Classification and grading of standards
4-1 Classification Classification:
① National standard GB ② industry standard YB ③ Local standard ④ Enterprise standard Q/CB
4-2 Classification:
① Product standard ② packaging standard ③ method standard ④ basic standard
4-3 Standard level (three levels) :
Class Y: International advanced level I: international general level H: domestic advanced level
4-4 GB
GB1220-84 stainless rod (Class I) GB4241-84 stainless Welding disk (Class H)
GB4356-84 Stainless Welding Disk (Class I) GB1270-80 stainless pipe (Class I)
GB12771-91 Stainless welded pipe (Grade Y) GB3280-84 stainless cold plate (Grade I)
GB4237-84 Stainless hot plate (Class I) GB4239-91 Stainless cold belt (Class I)

The main problem

Stainless steel corrosion

Electrochemical or chemical reactions occur on the metal surface exposed to corrosive environment and uniformly corroded. Stainless steel surface passivation film in the corrosion resistance of the weak part, due to the self-excited reaction and the formation of pitting reaction, the formation of small holes, coupled with chloride ions close to the formation of a strong corrosive solution, accelerate the speed of corrosion reaction. There are stainless steel internal intergranular corrosion cracking, all these, the passivation film on the surface of stainless steel are destroyed. Therefore, the stainless steel surface must be regularly cleaned and maintained in order to maintain its gorgeous surface and extend the service life. When cleaning the surface of stainless steel, attention must be paid to no surface scratch phenomenon, avoid the use of bleaching ingredients and abrasive detergent, steel wire balls, grinding tools, in order to remove the washing liquid, wash the surface with clean water after the completion of washing.
Stainless steel is formed by its surface of an extremely thin and solid fine stable chromium-rich oxide film (protective film). Prevent oxygen atoms from continuing to infiltrate and oxidize, and obtain corrosion resistance. If, for some reason, the film is constantly damaged, the oxygen atoms in the air or liquid will continue to dissolve out, forming loose iron oxide, and the surface of the metal will be subjected to continuous rust.
For cost consideration, many domestic manufacturers reduce chromium and nickel in stainless steel and increase the content of manganese. Experts believe that the reason why stainless steel can not rust, is because of the presence of chromium and nickel, reducing the content of these two components will reduce the anti-rust performance.

Notes in the process of stainless steel machining:

Processing area: stainless steel parts of the processing area should be relatively fixed. Protective measures should be taken on the platform of the processing zone, such as rubber MATS. Stainless steel parts processing should avoid damage to the surface protective layer of stainless steel parts.
Chlorine ions are present in the environment
Chloride ions are found in many places, such as salt/sweat/seawater/sea breeze/soil, etc. The corrosion of stainless steel in the presence of chloride ions is faster than that of ordinary mild steel. So there are requirements for the use of stainless steel environment, and the need to wipe often, remove dust, keep clean and dry. (That would give him a “improper use.”) In the United States, there is an example: an enterprise with an oak container containing a chloride ion solution, the container has been used for more than 100 years, the 1990s plan to replace, because the oak material is not modern enough, stainless steel replacement 16 days after the container due to corrosion leakage.
It has not undergone solution treatment
Alloying elements did not dissolve into the matrix, resulting in low alloying content and poor corrosion resistance.
Natural intergranular corrosion
This titanium – and niobium-free material has a tendency to intergranular corrosion. The intergranular corrosion can be reduced by adding titanium and niobium together with stabilization treatment. In the air or chemical corrosive medium can resist corrosion of a high alloy steel, stainless steel is a beautiful surface and good corrosion resistance, do not have to go through plating and other surface treatment, and play the inherent surface properties of stainless steel, used in many aspects of steel, usually known as stainless steel. Representative properties are 13 chromium steel, 18-8 chromium nickel steel and other high alloy steel. From the point of view of metallography, because the stainless steel contains chromium and the formation of a very thin chromium film on the surface, this film is isolated from the oxygen intrusion in the steel to play a role in corrosion resistance. In order to maintain the corrosion resistance inherent in stainless steel, the steel must contain at least 12% chromium. For welding applications, the lower carbon content minimizes the carbides precipitated in the heat-affected zone near the weld, which may lead to intergranular corrosion of stainless steel in some environments.
dust
Production is often carried out in a dusty field, often with a lot of dust in the air, they constantly fall on the surface of the equipment. They can be removed with water or alkaline solutions. However, grime with adhesion requires high-pressure water or steam for cleaning.
Iron powder or embedded iron
On any surface, free iron rusts and corrodes stainless steel. Therefore, it must be cleared. Float powder can generally be removed along with the dust. Some have strong adhesion and must be treated with embedded iron. In addition to dust, there are many sources of surface iron, including cleaning with ordinary carbon steel wire brush and shot peening with sand, glass beads or other abrasives previously used on ordinary carbon steel, low alloy steel or cast iron, or polishing of the aforementioned non-stainless steel products near stainless steel parts and equipment. Steel wire ropes, spares, and iron on workbench surfaces can easily embed or stain the surface if the stainless steel is not protected during loading or lifting. The presence of free iron can be prevented and detected by order requirements and post-production inspection. ASTM Standard A380[3] specifies the rust test method for the inspection of iron or steel particles on the surface of stainless steel. This test should be used when absolutely no iron is required. If the results are satisfactory, wash the surface with clean pure water or nitric acid until the dark blue disappears completely. As indicated in standard A380[3], if the rust test solution cannot be completely cleaned, this test method is not recommended for the process surface of the equipment, i.e. the direct contact surface used to produce human consumer goods. A relatively simple test method is to be exposed to water for 12 to 24 hours to check whether there are rust spots. Such tests are insensitive and time-consuming. These are detection tests, not cleanup methods. If iron is found, it must be cleaned up using the chemical and electrochemical methods described below.
The scratch
In order to prevent process lubricants or products and/or dirt accumulation, scratches and other rough surfaces must be mechanically cleaned generally with stainless steel polishing machine removal. If the stainless steel is heated to a certain high temperature in the air during the welding or grinding process, the chrome oxide heat recovery color will appear on both sides of the weld, the lower surface and the bottom of the weld. The reignition color is thinner than that of the protective oxide film, and obviously visible. Color depends on thickness and can be rainbow, blue, purple to pale yellow and brown. Thicker oxides are generally black. It is caused by staying at high temperatures or at higher altitudes for a long time. When any of these oxide layers are present, the chromium content of the metal surface decreases, resulting in reduced corrosion resistance in these areas. In this case, not only should the reignition color and other oxide layers be eliminated, but the chrome-poor metal layer beneath them should also be cleaned.
Rusty spot
Sometimes rust on stainless steel products or equipment can be seen before or during production, which indicates that the surface is seriously contaminated. Rust must be removed before the equipment is put into use, and thoroughly cleaned surfaces should be inspected by iron and/or water tests.
Rough grinding and machining
Grinding and machining can result in rough surfaces with grooves, overlaps and burrs. Each defect may also damage the metal surface to such a depth that the damaged metal surface cannot be removed by pickling, electro-polishing, or shot peening (e.g. dry sandblasting, abrasive glass beads). The rough surface can become the source of corrosion and deposition products. Cleaning weld defects or removing excess weld strengthening height before rewelding can not be ground with coarse grinding. In the latter case, fine abrasives should be used to grind.
Welding arc markings
When the welder starts the arc on the metal surface, it will cause surface roughness defect. The protective film is damaged, leaving a potential source of corrosion. The welder should arc in the already soldered path or on the side of the weld joint. The arc trace is then fused into the weld.
Welding splash
Welding spatter has a lot to do with the welding process. For example: GTAM (gas shielded tungsten arc welding) or TIG (inert gas shielded tungsten welding) no splash. However, improper use of welding parameters in GMAW (gas shielded metal arc welding) and FCAW (arc welding with flux core) welding processes will cause a lot of spatter. When this happens, the parameters must be adjusted. If the problem of welding spatter is to be solved, the splitter should be applied to each side of the joint before welding. This will eliminate the adhesion of the splash. After welding, it is easy to clean up the splashproof agent and all kinds of splashes without damaging the surface or causing minor damage.
Welding processes using flux include manual welding, arc welding with flux core and submerged arc welding. These welding processes will leave fine flux particles on the surface, which cannot be removed by ordinary cleaning methods. This particle will be the corrosion source of crevice corrosion, and the residual flux must be removed by mechanical cleaning method.
Defect of welding
Welding defects such as edge biting, incomplete penetration, dense porosity and cracks not only reduce the fastness of joints, but also become the corrosion source of crack corrosion. When cleaning operations are performed to improve this result, they also entrap solid particles. These defects can be repaired by re-welding or re-welding after grinding.
Oil and grease
Organic matter such as oil, grease and even finger marks can be a source of local corrosion. Because these substances act as barriers, they affect chemical and electrochemical cleaning effects and must be thoroughly removed. ASTM A380 has a simple WATERBREAK test to detect organic contaminants. When tested, water is poured from the top of a vertical surface, separating around the organic material as it flows down. Fluxes and/or acid chemical cleaners can remove oil stains and grease.
Residual adhesive agent
When the tape and protective paper are removed, some of the adhesive remains on the stainless steel surface. If the adhesive is not hard, it can be removed with organic flux. However, when exposed to light or air, the adhesive hardens and forms the corrosion source of crevice corrosion. Mechanical cleaning with fine abrasives is then required.
Paint pen printing
The effects of these pollutants are similar to those of oils and greases. It is recommended to wash with a clean brush and clean water or an alkaline cleaner, or to rinse with high-pressure water or steam. Stainless steel with mainly ferritic structure in service. Chromium content of 11%~30%, with body – centered cubic crystal structure. This kind of steel generally does not contain nickel, and sometimes contains a small amount of Mo, Ti, Nb and other elements. This kind of steel has the characteristics of large thermal conductivity, small expansion coefficient, good oxidation resistance, excellent stress corrosion resistance and so on. It is mostly used in the manufacture of parts resistant to atmospheric, water vapor, water and oxidizing acid corrosion. This kind of steel has some disadvantages such as poor plasticity, reduced plasticity after welding and corrosion resistance, which limit its application. The application of off-furnace refining technology (AOD or VOD) can greatly reduce the carbon, nitrogen and other clearance elements, so that this kind of steel has been widely used.

Influencing factors

Whether stainless steel plate or heat-resistant steel plate, Austenitic steel plate has the best comprehensive performance, both sufficient strength, and excellent plasticity while hardness is not high, which is also one of the reasons why they are widely used. Austenitic stainless steel is similar to most other metal materials, its tensile strength, yield strength and hardness increase with the decrease of temperature; Plasticity decreases with the decrease of temperature. Its tensile strength increases uniformly in the range of 15~80°C. More importantly, the impact toughness decreases slowly with the decrease of temperature, and there is no brittle transition temperature. So stainless steel at low temperature can maintain enough plasticity and toughness. The heat resistance of stainless steel refers to the oxidation resistance or corrosion resistance of gas medium at high temperature, that is, the thermal stability.
Effects of chromium
Chromium is the most important alloying element in austenitic stainless steel. The main reason for the anti-rust and anti-corrosion properties of austenitic stainless steel is that chromium promotes the passivation of steel and keeps the steel in a stable and blunt state under the action of mass. ○1 Effect of chromium on tissue: In austenitic stainless steel, chromium is an element that strongly forms and stabilizes the iron body, reducing the austenite region. With the increase of the content of steel, the ferrite (δ) structure can be found in austenitic stainless steel. The research shows that when the content of carbon is 0.1%, the content of chromium is 18%, in order to obtain a stable single austenitic structure, the minimum nickel content is required. About 8%, in this regard, the commonly used 18Cr — 8Ni type chromium nickel austenitic stainless steel is chromium, nickel amount ratio is the most suitable one. In austenitic stainless steel, with the increase of chromium content, the formation tendency of some intermetallic phases (such as δ phase) increases. When the steel contains molybdenum, the chromium content will increase and the formation of χ-equal phase will occur. As mentioned above, the precipitation of σ and χ-phase not only significantly reduces the plasticity and toughness of steel, but also reduces the corrosion resistance of steel under some conditions. With the increase of chromium content in austenitic stainless steel, the conversion temperature (Ms) of martensite to hydrocarbon decreases, thus improving the stability of austenitic matrix. Therefore, high chromium (such as more than 20%) austenitic stainless steel is difficult to obtain martensite structure even after cold processing and low temperature treatment.
Chromium is a strong carbide forming element, and it is no exception in austenitic stainless steel. Common chromium carbides in austenitic stainless steel are Cr23C6; When the steel contains molybdenum or chromium, carbides such as mature Cr6C can also be seen, and their formation will have an important effect on the properties of steel under certain conditions. 2 chromium on performance: Generally speaking, as long as austenitic stainless steel maintains complete austenitic structure without the formation of δ ferrite, only increasing the content of chromium in steel will not have a significant effect on the mechanical properties, chromium on the performance of austenitic stainless steel is the greatest impact on corrosion resistance, mainly as: chromium to improve the oxidation resistance of steel and acid chloride medium performance; Under the combined action of Ni, Mo and Cu, Cr improves the resistance of steel to some reducing media, organic acids, urea and alkali media. Chromium also increases steel resistance to local corrosion, such as intergranular corrosion. Point corrosion, crevice corrosion and stress corrosion under certain conditions. The most important factor affecting the intergranular corrosion sensitivity of austenitic stainless steel is the content of carbon, and the effect of other elements on the intergranular corrosion mainly depends on its influence on the dissolution and precipitation behavior of carbide. In austenitic stainless steel, chromium can increase the solubility of carbon and reduce the dilution degree of chromium, so increasing the content of chromium is beneficial to the intergranular corrosion resistance of austenitic stainless steel. Chromium is very effective in improving the point corrosion resistance and crevice corrosion resistance of austenitic stainless steel, when there is molybdenum or molybdenum and nitrogen in the steel, the effectiveness of chromium greatly enhanced, although according to the study of molybdenum point corrosion resistance and crevice corrosion ability is about 3 times of chromium, nitrogen is 30 times of chromium, but a large number of studies, if there is no chromium in austenitic stainless steel or chromium content is low, The point and gap corrosion resistance of molybdenum and nitrogen will be lost or not significant enough.
The effect of chromium on the stress corrosion resistance of austenitic stainless steel varies with the conditions of the experimental medium and the actual application environment. In the boiling solution of MgCl2, the effect of chromium is generally harmful, but in the water medium containing Cl- and oxygen, the high temperature and high pressure water and the stress corrosion conditions originating from the point corrosion, increasing the chromium content in the steel is beneficial to the stress corrosion resistance. Chromium can also prevent the tendency of intergranular stress corrosion in austenitic stainless steel and alloy due to the increase of nickel content, and the effect of chromium on cracking (NaOH) stress corrosion is also beneficial. Chromium has an important effect on the corrosion resistance of austenitic stainless steel, but also can significantly improve the corrosion resistance of austenitic stainless steel oxidation, vulcanization and melting salt corrosion properties.
Influence of nickel
1 Effect of nickel on tissue
Nickel is an element that strongly stabilizes austenite and expands the austenitic phase region. In order to obtain a single austenitic structure, the minimum nickel content required is about 8% when the steel contains 0.1% carbon and 18% chromium. This is the basic component of the most famous 18-8 chromium-nickel austenitic stainless steel. And significantly reduce the tendency of σ phase formation; At the same time, the temperature of martensitic hydrocarbon transfer decreases, or even the λ-M phase transition does not occur, but the increase of nickel content will reduce the solubility of carbon in austenitic stainless steel, so that the carbide precipitation tendency is enhanced.
2 Influence of nickel on properties
The influence of nickel on the mechanical properties of austenitic stainless steel, especially on chromium-nickel austenitic stainless steel, is mainly determined by the influence of nickel on the stability of austenitic steel. In the range of nickel content where martensitic transformation may occur in steel, the strength of steel decreases and the plasticity increases with the increase of nickel content. Chromium nickel austenitic stainless steel with stable austenitic structure has excellent toughness (including extremely low temperature toughness), so it can be used as low temperature steel, it is known that for chromium manganese austenitic stainless steel with stable austenitic structure, the addition of nickel can further improve the toughness. Nickel can also significantly reduce the cold working hardening tendency of austenitic stainless steel, which is mainly due to the increase of austenitic stability, reduce and eliminate the martensite transformation in the cold working process, at the same time, the cold working hardening effect of austenitic itself is not obvious, the influence of cold working hardening tendency of stainless steel, nickel reduces the cold working hardening rate of austenitic stainless steel, The effect of reducing the strength of steel at room temperature and low temperature and improving the plasticity determines that the increase of nickel content is beneficial to the cold working formability of austenitic stainless steel, and the increase of nickel content can also reduce or eliminate the δ ferrite in 18-8 and 17-14-2 crNi austenitic stainless steel, so as to improve its hot working performance. The decrease of δ ferrite has an adverse effect on the weldability of these steels and increases the tendency of welding hot crack wires. In addition, nickel can also significantly improve the thermal working performance of chromn-mn nitrous austenitic stainless steel, and thus significantly improve the yield of steel. In austenitic stainless steel, the addition of nickel and the increase of nickel content lead to the increase of the thermodynamic stability of steel. Therefore, austenitic stainless steel has better rust resistance and oxidation resistance of the performance of the medium, and with the increase of nickel content, the performance of the reducing resistance of the medium has been further improved. It is worth pointing out that nickel is also the only important element to improve the corrosion resistance of austenitic stainless steel in many media. The influence of nickel on the corrosion resistance of austenitic stainless steel in various acid media should be pointed out that under some conditions of high temperature and high pressure water, the increase of nickel content leads to the increase of the intergranular stress corrosion sensitivity of steel and alloy. However, this adverse effect can be alleviated or inhibited by the increase of chromium content in steel and alloy. With the increase of nickel content in magnetic carnae austenitic stainless steel, the critical carbon content of intergranular corrosion decreases, that is, the sensitivity of steel to intergranular corrosion increases. As for the resistance of austenitic stainless steel to point corrosion and crevice corrosion, nickel has no significant effect. In addition, nickel also improves the oxidation resistance of austenitic stainless steel at high temperature, which mainly improves the composition of chromium oxide film with nickel. The structure and performance are reduced, and the higher the nickel content, the more harmful, this is mainly due to the low melting point of nickel sulfide at the grain boundary in the steel, generally speaking, simple chromium nickel (and chromium manganese nitrogen) austenitic stainless steel is only used for the use of rust and oxidation resistance of the medium (such as nitric acid, etc.), Molybdenum, as an important alloying element in austenitic stainless steel, is added to steel to further expand its use range. The main role of molybdenum is to improve steel in reducing medium
Effect of molybdenum
1. Effect of molybdenum on tissue
Molybdenum and chromium are both elements that form and stabilize ferrite and expand the ferrite phase region. Molybdenum has the same capacity to form ferrite as chromium. Molybdenum also promotes the precipitation of intermetallic phases in austenitic stainless steel, such as σ phase, κphase and Laves phase, which has adverse effects on the corrosion resistance and mechanical properties of steel, especially resulting in the reduction of plasticity and toughness. In order to maintain a single austenitic structure in austenitic stainless steel, with the increase of molybdenum content in steel, the content of austenitic forming elements (nickel, nitrogen and manganese, etc.) should be increased accordingly, so as to maintain the balance between ferrite and austenitic forming elements in steel.
2. Effect of molybdenum on properties
The oxidation effect of molybdenum on austenitic stainless steel is not significant, so when the chromium nickel austenitic stainless steel maintains a single austenitic structure and no intermetallic precipitation, the addition of molybdenum has little effect on its mechanical properties at room temperature. However, with the increase of molybdenum content, the high temperature strength of steel is improved, such as durability, creep and other properties are greatly improved. Therefore, stainless steel containing molybdenum is often applied at high temperature. However, the addition of molybdenum increases the deformation resistance of steel at high temperature, and there is often a small amount of δ ferrite in steel, so the hardness of stainless steel containing molybdenum is worse than that of steel without molybdenum, and the higher the content of molybdenum, the worse the thermal working performance, in addition, molybdenum austenitic stainless steel is prone to κ(σ) phase precipitation, which will significantly deteriorate the plasticity and toughness of steel. Therefore, in the process of production, equipment manufacturing and application of molybdenum-containing austenitic stainless steel, attention should be paid to prevent the formation of intermetallic phases in steel. Although molybdenum action is an alloying element to the reducing medium of austenitic stainless steel, the cause of surface corrosion and crevice corrosion is not completely clear, but a large number of experiments have pointed out that the corrosion resistance of molybdenum is only effective when the steel contains a high amount of chromium. Molybdenum is mainly used to strengthen the corrosion resistance of chromium in steel. Meanwhile, the corrosion inhibition effect of molybdenum after forming acid salts has been proved by experiments. In the aspect of stress corrosion resistance of highly concentrated chloride solution, although molybdenum, as an alloying element, is resistant to reducing medium of austenitic stainless steel, and the reasons for its resistance to point corrosion and crevice corrosion are not completely clear, a large number of experiments have pointed out that, The effect of molybdenum is only effective when the steel contains a high amount of chromium, molybdenum is mainly to strengthen the corrosion resistance of chromium in steel, at the same time, the buffering effect of molybdenum after forming molybdate has been proved by experiments, in the aspect of stress corrosion resistance of high concentration chloride deposition, although this experiment refers to the same. Molybdenum below 3# is harmful to the stress corrosion resistance of austenitic stainless steel, but because the common chromium nickel austenitic stainless steel is mostly used in the water medium containing trace chloride and saturated oxygen, its stress corrosion and point corrosion as the origin, so the molybdenum bearing chromium nickel molybdenum austenitic stainless steel due to high point corrosion resistance, Therefore, in practical application, steel with no molybdenum often has better resistance to chloride stress corrosion.

Process of development

The development progress of our stainless steel industry is relatively late, since the founding of our country to the reform and opening up, the demand of our stainless steel is mainly based on the use of industry and national defense cutting-edge. After the reform and opening up, the rapid development of the national economy, the significant improvement of people’s living standards, pull the demand for stainless steel. After entering the 1990s, China’s stainless steel industry has entered a period of rapid development, the growth rate of stainless steel demand is much higher than the global level. Since 1990, the global apparent consumption of stainless steel has been growing at an average annual rate of 6%, and in the decade of 1990s, the apparent consumption of stainless steel in China was 2.9 times of the world average annual growth rate. Entering the 21st century, our stainless steel industry increased rapidly.
From 2000 to 2006, the average annual growth rate of stainless steel consumption was more than 21.17%. Among them, in 2001, the apparent consumption of stainless steel reached 2.05 million tons, surpassing the United States to become the world’s first stainless steel consumption country. In 2008, China’s apparent consumption of stainless steel reached 6.24 million tons, down 5.17 percent year-on-year.
In November 2011, China’s stainless steel production increased by 11.1% to 12.5 million tons. The production of stainless steel products 336,800 tons, a year-on-year increase of 65.25%. Among them, Guangdong Province is the main production base of stainless steel products, its output reached 1.837 million tons, an increase of 41.76% year-on-year, accounting for 78.62% of the national total.
Stainless steel is the most widely used in the world today, the best performance price ratio of steel surface treatment method.
With the implementation of the western development strategy, the development of power transmission from west to east, gas transmission from west to east, water diversion from south to north, the Three Gorges Project, the transformation of rural power grid and urban power grid, our stainless steel industry has entered a new stage of rapid development.
The chromium nickel in the raw material of our stainless steel industry in the foreign country is more than demand, but in our country, the demand exceeds supply; Stainless steel is overcapacity, supply exceeds demand, profit space fluctuates frequently. With the increasing competition in the stainless steel industry, mergers and acquisitions and capital operation among large stainless steel production enterprises are becoming more and more frequent. The domestic excellent stainless steel production enterprises are paying more and more attention to the research of the industry market, especially the in-depth study of the development environment of enterprises and the change of customer demand trend. Because of this, a large number of domestic excellent stainless steel brands rise rapidly, gradually become the leader in the stainless steel industry!
Operation of iron and steel industry
1. Output reached a record high. During the first six months of 2013, China produced 390 million tons of crude steel, up 7.4% year on year and 5.6 percentage points higher than the same period in 2012. In the first six months, the average daily crude steel output was 2.154 million tons, equivalent to the annual crude steel output of 786 million tons. Among them, February reached a record high of 2.208 million tons, March to June although there was a decline, but still maintained at a high level of more than 2.1 million tons. From January to June, the crude steel output of Hebei and Jiangsu increased by 6.8% and 13.2%, respectively, year-on-year. The new output of the two provinces accounted for 42.4% of the national increase of 26.94 million tons. Shanxi, Liaoning, Henan and Yunnan provinces also increased by more than 1 million tons. From January to June, the crude steel output of key large and medium-sized steel enterprises increased by 5.5% year on year, 2 percentage points lower than the national average, but 60% of the increase still came from key large and medium-sized steel enterprises.
(2) Low steel price operation. From January to June 2013, the overall performance of the domestic steel market was depressed. With the substantial release of crude steel capacity, the market supply and demand fall into an imbalance, steel prices into the declining channel, has been weak down for more than 4 months. By July 26, 2013, the steel price index dropped to 100.48 points, down from 6.6 points at the beginning of the year. Iron and Steel Industry association key statistics of eight varieties of steel prices at the beginning of the year all have different degrees of decline, an average decline of 5.7%. By variety, the price of construction wire and spiral steel, which account for a large proportion of Chinese steel production, fell by 4.9% and 6.7% respectively, while the price of medium thick plate and hot rolled coil fell by 5.7% and 9.7% respectively.
(3) The export of steel increased rapidly. The imbalance of supply and demand in the domestic steel market stimulates enterprises to export. From January to June, the country exported 30.69 million tons of steel, up 12.6% year on year; China imported 6.83 million tons of steel, down 1.8 percent, and imported 320,000 tons of billets and ingots, up 50 percent. Converting billet into rough steel, the cumulative net export of 25.06 million tons, up 17.3% year on year, accounting for 6.4% of our crude steel output. From the perspective of export price, the average export price of rod and wire from January to June was 624.3 USD/ton, down 18% year-on-year. The sheet was 835.2 USD/ton, down 2.8% year-on-year.
(4) Steel mills and social inventory high operation. The contradiction between supply and demand in the market spreads to the circulation field, and the domestic steel inventory continues to grow at the end of last year. On March 15, it reached a record high of 22.52 million tons, an increase of 3.51 million tons over the previous year’s peak, among which the construction steel inventory of 14.32 million tons, accounting for 63.6% of the total inventory. After that, as seasonal consumption increased, inventories gradually fell to 15.4 million tons on July 26. In mid-March, the steel inventory of key enterprises hit a record, reaching 14.51 million tons, up 29.7 percent year on year. In late June, it fell to 12.68 million tons, still 29.9 percent higher than the beginning of the year and 11.4 percent higher than the same period in 2012.
(5) The profitability of steel mills is declining month by month. In the first half of 2013, the metallurgical industry achieved a profit of 73.69 billion yuan, up 13.7% year on year, among which the ferrous metal smelting and calendering industry achieved a profit of 45.44 billion yuan, up 22.7% year on year. From January to May, the profitability of key large and medium-sized steel enterprises was far lower than the overall level of the industry, and showed a month-on-month decline. Although the profit increased by 34%, it was only 2.8 billion yuan, and the sales profit margin was 0.19%. In May, 86 key large and medium-sized steel enterprises only achieved a profit of 150 million yuan, five consecutive months of month-on-month decline, 34 of them in the red, the loss of up to 40%.
(6) The growth rate of fixed asset investment in the steel industry dropped significantly. From January to June 2013, the fixed asset investment in the iron and steel industry was 303.5 billion yuan, a year-on-year growth of 4.3%, among which the ferrous metal smelting and calendering investment was 235.6 billion yuan, a year-on-year growth of 3.3%, 6.1 percentage points lower than the same period in 2012; The investment in black metal mining was 67.9 billion yuan, up 7.8% year on year, or 15 percentage points lower.
Theoretical weight calculation of stainless steel products
Stainless steel/steel strip reference formula: stainless steel plate weight (kg) = length (m) * width (m) (mm) * * thick density rho (g/cm after).
Stainless steel round bar/wire reference formula: stainless steel round bar weight (kg) = (diameter (mm) / 2) * (diameter (mm) / 2 * PI * long (m) * rho density (g/cm after) / 1000.
Stainless steel pipe reference formula: stainless steel pipe weight (kg) = ((outside diameter (mm) / 2) * (outside diameter (mm) / 2) – (inside diameter (mm) / 2) * (inside diameter (mm) / 2)) * PI * long (m) * rho density (g/cm after) / 1000; ** Wall thickness (mm)=(outer diameter (mm)- inner diameter (mm))/2.
Stainless steel square tube reference formula: stainless steel square tube weight (kg) = (section length (mm) (mm) * 2 * 2 – cross section width – thickness (mm) * 4) * wall thickness (mm) * (m) * rho density (g/cm after) / 1000.
Stainless steel equilateral Angle steel reference formula: stainless steel equilateral Angle steel weight (kg) = (section length (mm) * 2 – edge thickness (mm) * (m) * rho density (g/cm after) / 1000; **[1] According to the national standard GB/T706-2008 of equilateral Angle steel, the actual weight calculation formula of Angle steel is complicated. Since the inner arc radius (r1) and inner arc radius (r) of the side end in the section of Angle steel are not specified in GB/T706-2008 as delivery conditions, this reference formula is given in combination with the actual delivery status of Angle steel in production circulation. [2] in 2008, according to GB/T706 – given the equal Angle of cross section area calculation formula is: S = d * (2 * b – d) + 0.215 * (r squared – 2 r1 squared), accurate theory of stainless steel equilateral Angle steel weight (kg) = section area S squared (mm) * (m) * rho density (g/cm after) / 1000.
Stainless steel equilateral Angle steel reference formula: stainless steel equilateral Angle steel weight (kg)=(section side length 1(mm)+ section side length 2(mm)- side thickness (mm))* length (m)* density ρ(g/cm³)/1000; **[1] According to the national standard GB/T706-2008 for unequal Angle steel, the actual weight calculation formula of Angle steel is complicated. Since the inner arc radius (r1) and inner arc radius (r) of the side end in the section of Angle steel are not specified in GB/T706-2008 as delivery conditions, this reference formula is given in combination with the actual delivery status of Angle steel in production circulation. [2] According to GB/T706-2008 given unequal Angle section area calculation formula: S=d*(B+ b-D)+0.215*(r²-2r1²), accurate stainless steel unequal Angle theoretical weight (kg)= section area S(mm²)* length (m)* density ρ(g/cm³)/1000.
Stainless steel channel steel reference formula: stainless steel channel steel weight (kg) = (section height (mm) * section waist thickness (mm) + (cross section of the leg width (mm) – section waist thickness (mm)) * section average leg thickness (mm) * 2) * (m) long * rho density (g/cm after) / 1000; [1] According to the channel steel national standard GB/T706-2008, the actual weight calculation formula of channel steel is complicated. Since the inner arc radius (r1) and inner arc radius (r) of the side end of the channel steel section are not specified in GB/T706-2008 as delivery conditions, this reference formula is given in combination with the actual delivery status of channel steel in production circulation. [2] according to GB/T706-2008 channel cross section area of the given in formula: S = d + 2 h * * t * (b, d) + 0.349 (r squared – r1 squared), accurate theory of stainless steel channel steel weight (kg) = section area S squared (mm) * (m) * rho density (g/cm after) / 1000.
Stainless steel beams reference formula: stainless steel beams weight (kg) = (section height (mm) * section waist thickness (mm) + (cross section of the leg width (mm) – section waist thickness (mm)) * section average leg thickness (mm) * 2) * (m) long * rho density (g/cm after) / 1000; [1] According to the I-beam national standard GB/T706-2008, the actual weight calculation formula of I-beam is more complicated. Since the inner arc radius (r1) and inner arc radius (r) of the side end of the I-beam section specified in GB/T706-2008 are not taken as delivery conditions, this reference formula is given in combination with the actual delivery status of the I-beam in production and circulation. [2] according to GB/T706-2008 given in i-steel section area calculation formula: S = d + 2 h * * t * (b, d) + 0.615 (r squared – r1 squared), precise stainless steel beams theoretical weight (kg) = section area S squared (mm) * (m) * rho density (g/cm after) / 1000.
Stainless steel reference formula: L stainless steel weight (kg) = L (long edge width (mm) * long edge thickness (mm) + (short edge width (mm) – long edge thickness (mm)) * short edge thickness (mm)) * long (m) * rho density (g/cm after) / 1000; [1] According to the national L-section steel standard GB/T706-2008, the actual weight calculation formula of L-section steel is complicated. Although the inner arc radius (r1) and inner arc radius (r) of the side end in the section of L-shaped steel are not specified in GB/T706-2008, this reference formula is given in combination with the actual delivery status of L-shaped steel in production and circulation. [2] according to GB/T706-2008 L steel cross section area of the given in formula: S = B * D + D * (B, D) + 0.215 * (r squared – r1 squared), precise stainless steel L theoretical weight (kg) = section area S squared (mm) * (m) * rho density (g/cm after) / 1000.
Stainless steel square reference formula: stainless steel square weight (kg)= section length (mm)* section width (mm)* length (m)* density ρ(g/cm³)/1000.
Stainless steel wire rope reference formula: stainless steel wire rope weight (kg)= diameter (mm)* diameter (mm)* 100 meter coefficient * length (m)/100.