How is the yield point of the seamless square tube calculated? The metal material with yielding phenomenon, the force of the sample does not increase (maintains constant) during the stretching process, and the stress at the time of elongation can be continued, which is called the yield point. If the force drops, the upper and lower yield points should be distinguished. The unit of yield point is N/mm2 (MPa). Yield point on the square tube (σsu): the maximum stress before the sample yields and the force drops for the first time; Yield point under the square tube (σsl): The minimum stress in the yielding stage when the initial transient effect is not counted. The calculation formula for the yield point is: Where: Fs--the yield force (constant) during the tensile process of the specimen, N (Newton); So--the original cross-sectional area of the sample, mm2.

In the increasingly fierce and increasingly cruel competition in the low-alloy tube steel market at home and abroad, we insist on constantly innovating management and constantly innovating technology to continuously overcome new challenges and win new developments that are good and fast. During the "Twelfth Five-Year Plan" period, we should also have more awareness of the crisis. I have two suggestions: First, it is recommended that the state should advocate the use of steel structures in construction projects, which is conducive to energy conservation and emission reduction and recycling of 20G steel pipe resources to achieve sustainable development. We must pay attention to and solve these imbalances, and focus on solving the problems of overcapacity of 15crmog alloy tubes caused by repeated construction, and ensure the sustained, healthy and stable development of the national economy. In addition, during the “Twelfth Five-Year Plan” period, there are still many things to be done in the steel industry, such as the development of 12cr1movg alloy tube raw materials. First of all, we must make good use of domestic mineral resources, strengthen all aspects of work, and seek more support so that domestic mines can be scientifically and greenly exploited. Now, there is some waste in the development of domestic mines, and it also has a certain impact on the environment. This situation should be changed as soon as possible. It should be specially pointed out that it is very difficult to control the resources “going out” now, and 16mn seamless steel pipe enterprises should have a full understanding of this. Facing the new opportunities during the “Twelfth Five-Year Plan” period, the No. 45 seamless pipe steel industry should adhere to the principle of accelerating the transformation of economic development mode and take the road of scientific development of industrial structure and product structure.

1 Precision welded pipe with small internal burrs: An important aspect of the quality of precision welded pipe products is the removal of burrs in the weld. Due to the limited space position, the internal burr removal of small diameter welded pipes has always been a technical difficulty in the welded pipe manufacturing industry. Therefore, selecting the appropriate welding method from the welding technology is an effective way to solve the problem. The welding methods for producing small internal burrs are DC welding method and square wave resistance welding method. These welding methods have the characteristics of uniform heating, smooth weld seam, good quality, and small internal burr formation, generally only 0.1 to 0.2 mm.   2 Micro-beam plasma method to produce high-precision ultra-thin wall welded pipe: The micro-bundle plasma method is used to weld extremely thin-wall welded pipes. The outer weld is bright and smooth, the inner weld is flat and compact, the burr height is no more than 0.031-0.020mm, and the outer diameter of the steel pipe after welding is 0.10-0.23mm, and the wall thickness difference is 0.020. ~0.034mm, after cold rolling, the outer diameter ellipticity is effectively eliminated, the wall thickness difference is 0.002~0.007mm, and the quality completely reaches the level of precision seamless thin-walled tube. After heat treatment, it has the same structure and properties as the seamless tube, and the economical superiority of producing a very thin tube with a seamless tube is much less than that of a very thin tube after cold rolling.   3 High-strength welded pipes for the automotive industry: In recent years, the automobile industry at home and abroad has promoted lightweight vehicles to save energy, and it is urgent to replace solid parts with high-strength hollow parts. It is technically feasible to develop high-strength welded pipes instead of seamless pipes to meet the needs of the automotive industry. In the development of high-strength welded pipes for the automotive industry, Japan has successively developed series of steel grades such as C-Ti-B, C-Mn-Nb and C-Cr-AI-B, and adopted different heat treatment systems according to different purposes. Such as annealing, normalizing and quenching, tempering, etc. It is used in high strength welded pipes of automobile industry, and its standard strength grades are 561MPa, 637MPa, 980MPa and so on. In addition to high strength, the welded pipe is also required to have high plasticity, good workability, hardenability, toughness and fatigue strength.

The national long product index was 166.4, up 0.13% on a week-on-week basis and up 3.36% month-on-month, down 12.29% from the same period last year. The national plate index was 136.2, up 0.11% on a week-on-week basis and up 3.07% month-on-month, down 3.52% from the same period last year. For long products: The national high-line index was 161.8, up 0.29% on a week-on-week basis, up 3.16% month-on-month, and down 13.46% from the same period last year. The national rebar index was 170.3, which was the same as last week, and rose by 3.52% year-on-year, down 11.33% from the same period of last year. For sheet metal: the national mid-board index was 144.9, up 0.14% on a week-on-week basis, up 4.48% month-on-month, and down 6.11% from the same period last year. The national hot rolled index was 144, up 0.02% on a week-on-week basis and up 2.99% month-on-month, down 2.14% from the same period last year. The national cold plate index was 116.2, up 0.38% on a week-on-week basis, up 3.04% month-on-month, and down 8.89% from the same period last year. The national galvanized sheet index was 106.9, up 0.33% on a week-on-week basis and up 1.19% on a year-on-year basis, down 3.25% from the same period last year. From a regional perspective, the North China Index was 153.4, up 0.56% on a week-on-week basis, up 4.57% on a year-on-year basis, and down 8.45% year-on-year. The Northeast Index was 147.5, up 0.19% on a week-on-week basis, up 4.72% year-on-year, and down 10.22% year-on-year. The East China Index was 150.6, down 0.01% on a week-on-week basis, up 2.91% year-on-year, and down 8.06% year-on-year. The Central China Index was 155, up 0.11% on a week-on-week basis, up 1.95% year-on-year, and down 10.24% year-on-year. The South China Index was 161.6, down 0.13% on a week-on-week basis, up 3.09% on a year-on-year basis, and down 8.31% year-on-year. The Southwest Index was 156.4, up 0.09% on a week-on-week basis, up 1.70% year-on-year, and down 10.19% year-on-year. The Northwest Index was 145, down 0.01% on a week-on-week basis, up 3.89% year-on-year, and down 11.79% year-on-year.

Although the winter in previous years was the off-season of steel consumption, due to the existence of winter storage market, winter steel price performance is still worth looking forward to. However, the winter storage situation in 2013 is expected to fall short of expectations. The main reasons for making the above judgments are: the steel market is more pessimistic, the market winter willingness is insufficient; after the steel traders lose money, the funds are scarce, and the bank tightens the loan. Tightening the waistband of steel traders, insufficient funds also make it difficult for steel traders to carry out winter storage. No matter whether it is motivation or ability, it does not support steel traders and consumer enterprises to carry out winter storage. In the case that the winter storage market is hard to expect and steel consumption enters the off-season, it is expected that the demand for steel will be difficult to improve. Before the end of the year, the probability of low price consolidation of steel prices is large, and it is difficult for coking coal and coke to form an upward breakthrough. According to the latest data of China Steel Association, the average daily crude steel output in the first ten days of December continued the downward trend in November, with a preliminary estimate of 2.0129 million tons, down 3.7% from the previous month. This figure is significantly lower than the first 10 months of 2013. The average level. Regardless of whether the data is accurate or not, the data itself reflects the downward trend of crude steel production, and the decline in crude steel production means that the steel producers have reduced the demand for coking coal and coke, which has directly caused a negative impact on the coal char data. . If steel production continues to decline, the spot market for coal char will not be optimistic.

In 2013, the demand growth of the steel pipe industry was lower than expected, while the growth rate of production remained unchanged. The domestic market was still oversupply; the price of steel pipes fluctuated at a low level, and the prices of raw materials remained at a high level. Enterprises still have not shaken off the severe operating situation of low profits or losses. However, industry insiders said that the overall market environment of the steel pipe industry in 2014 is better than that in 2013, and the oil and gas pipeline will continue to prosper. The steel pipe market will continue to grow, and the oversupply situation will ease. In 2014, the environment of the steel pipe industry improved, and the oil and gas pipeline continued. "(2014) The development environment of the steel pipe industry and the oversupply of the market will be alleviated, but there will be no fundamental changes." Zhong Xidi, Secretary General of the Steel Structure Branch of China Steel Structure Association, made the above remarks on the 2014 steel pipe industry. It is reported that China's steel pipe production capacity exceeds 100 million tons. Since 2012, the utilization rate of steel pipe capacity has only been 75.95%, which is close to or exceeds the lower limit, and the production capacity has become excessive. Zhong Xidi further explained that from the current situation, the domestic and international economy will grow steadily, and the downstream management industry will continue to maintain rapid development. In addition, some stable growth policies and measures that have been introduced in 2013 will be further developed in 2014, and demand growth will continue. The steel pipe market will continue to grow, and the overall market environment of the steel pipe industry is better than that of 2013. As far as steel pipe varieties are concerned, the industry believes that the demand for energy in the oil and gas pipelines will continue to prosper and drive the overall demand for steel pipes. Zhong Xidi said that the demand for oil and gas pipelines still dominates the energy demand management. With the further expansion of global oil and gas exploration investment, the demand for oil and gas pipelines continues to grow, such as oil well pipes and pipelines. The demand for energy industries such as the delivery of fluid pipes continues to drive the overall demand for steel pipes." According to the forecast report of the Metallurgical Industry Planning Institute, the actual consumption of steel in China in 2014 was 715 million tons, up 3.2% year-on-year; the energy industry consumption was 32 million tons, second only to the automobile industry of 50.2 million tons, up 3.2% year-on-year. Xu Weidong, deputy general manager and director of Yulong Co., Ltd. (601028.SH), also told the Great Wisdom News Agency that the total demand for oil and gas pipelines during the 12th Five-Year Plan period is abundant, and there is confidence in 2014 and 2015; 2013-2015 More than 40,000 kilometers have not been completed, and it is expected to drive more than 10 million tons of oil and gas pipelines. In 2014 and 2015, market demand will be accelerated. A brokerage analyst who has long tracked oil and gas pipelines told Dazhi News Agency that the oil and gas pipeline industry will have a good climate of 3-5 years from 2012 on the oil and gas pipeline network and urbanization construction. In the A-share oil and gas pipeline sector, the three leading listed companies' performance in the third quarter of 2013 was full, and the net profit in the first three quarters all exceeded 20%. Yulong shares (601028.SH), Jiuli special materials (002318.SZ), Jinzhou Pipeline (002443.SZ) total revenue for the first three quarters of this year was 6.627 billion yuan, an increase of 6.84% over the same period, the combined net profit was 360 million yuan. , an increase of 26.7% over the same period. In 2013, the capacity utilization rate of steel pipes was close to the lower limit, and the demand for product upgrade adjustment was strong. The steel pipe industry in 2013 is still a difficult year: overcapacity, high cost, low efficiency, increased trade friction and urgent product upgrades are the key words of the 2013 steel pipe industry. Zhong Xidi said that it is expected that the output of steel pipes will exceed 80 million tons in 2013. However, the current capacity utilization rate is close to or exceeds the lower limit, showing overcapacity, but the export steel pipe grade is in urgent need of further adjustment and optimization. "In the first 10 months of 2013, although the export of steel pipes showed an increase in price and price, the average export price was still much lower than the average import price. The average import price of steel pipes was 3.31 times the average export price." Zhong Xidi said. It is reported that in January-October 2013, the export of steel pipes was 7,546,600 tons, a net increase of 146,000 tons, an

How is the yield point of the seamless square tube calculated? The metal material with yielding phenomenon, the force of the sample does not increase (maintains constant) during the stretching process, and the stress at the time of elongation can be continued, which is called the yield point. If the force drops, the upper and lower yield points should be distinguished. The unit of yield point is N/mm2 (MPa). Yield point on the square tube (σsu): the maximum stress before the sample yields and the force drops for the first time; Yield point under the square tube (σsl): The minimum stress in the yielding stage when the initial transient effect is not counted. The calculation formula for the yield point is: Where: Fs--the yield force (constant) during the tensile process of the specimen, N (Newton); So--the original cross-sectional area of the sample, mm2.

1. Generally, carbon steel is a domestic seamless steel pipe provided according to the characteristics of the product organization. GB/T700-88A steel is selected (but the sulfur content must not exceed 0.050%, and the phosphorus content should not exceed 0.045%), and its mechanical properties should meet the The value required in the GB8162-87 table. ​​ 2. The domestic seamless pipeline should be determined as the standard hydraulic test according to the hydraulic test. ​​ 3. The technical performance inspection of imported seamless steel pipes shall comply with the relevant specifications stipulated in the contract. ​​ 2. Main use 2.1. Seamless steel pipes are universal. Ordinary seamless steel pipe is cold-rolled from ordinary carbon alloy structural steel, low alloy tool steel or alloy tool steel. ​​ 2.2. The products supplied according to the main purpose are divided into three categories: a, according to the composition and mechanical properties, b, according to the mechanical properties, c, according to the hydrostatic test. According to the seamless steel pipes provided by grades a and b, in order to better withstand the liquid pressure, a hydrostatic test must also be carried out. ​ Special seamless steel pipes include seamless steel pipes for heating furnaces, seamless steel pipes for geological environments, and seamless steel pipes for crude oil. ​ Third, type. ​​ According to the difference in production, seamless steel pipes can be divided into hot-rolled pipes, cold-rolled pipes, cold-drawn pipes, extruded pipes, etc. ​​ According to the appearance design, it is divided into round tube, special-shaped tube, etc. In addition to square tubes and rectangular square tubes, there are also stainless steel round tubes, semi-circular tubes, triangular tubes, hexagonal tubes, convex tubes, plum blossom tubes, etc. ​​ According to the different raw materials, it is divided into ordinary carbon structural pipe, alloy structural steel structural pipe, high-quality carbon structural pipe, aluminum alloy structural pipe, stainless steel pipe, etc. ​​ 3.4. According to its unique main purpose, there are steam pipes, geological pipes, oil pipelines, etc.

In the actual trade environment, the quality of Jiangsu seamless steel pipes is uneven, and there are many fake and shoddy products, so how to identify the thick wall of seamless steel pipes? The following is an introduction: ​​ The surface of fake and inferior seamless steel pipes often has pockmarks. ​​ The flat surface refers to the irregular raised defects on the surface of Jiangsu seamless steel pipe due to severe groove wear. This is because Jiangsu seamless steel pipe production enterprises pursue profits excessively, and the groove rolling process has not been replaced. ​​ The surface of fake and inferior seamless steel pipes is easy to form scars ​​ There are two reasons for this situation: on the one hand, the quality of Jiangsu seamless steel pipes with poor quality is uneven, and there are many impurities; Scar on the surface of the stainless steel pipe. ​​ The surface of fake and inferior wood is prone to cracks ​​ The reason for the cracks is that the green body is adobe, and the adobe has large pores. The adobe is affected by thermal stress during the cooling process, and it is easy to crack, which makes the stainless steel tube crack after rolling.

Public Steel: Production continues to drop, and demand is expected to be released after the epidemic improves