What causes the brittle fracture of 16mn thick walled seamless steel pipe?

Sometimes there will be cracks, inclusions, porosity and other defects in the structure of 16mn seamless steel pipe, which can be regarded as microcracks in the material. In addition, brittle fracture is also related to the service temperature of the component. The pickling solution selected in the pickling process of 16mn seamless steel pipe is generally a mixture of a variety of acids, mainly sulfuric acid, nitric acid and hydrofluoric acid, etc., these mixed acids are very corrosive and have strong oxidation, and the temperature of the corrosive medium is also relatively high, which puts forward high requirements for the corrosion resistance of anti-corrosion materials.

There are many anti-corrosion materials suitable for 16mn thick-walled steel pipes, among which the best ones are epoxy resin and its modified resin. The principle of pickling 15crmo alloy pipe is to use acidic liquid to remove the oxide skin on the surface of the pretreated 16mn seamless steel pipe, remove the metal ions on the surface, and make it have a beautiful finish. Due to the defects such as cracks in the hot-rolled tube blank or after the high-precision cold-drawn tube is made into an oil cylinder, there is almost no plastic deformation occurs, and it is generally brittle fracture.

Brittle fracture is caused by a variety of causes. For example, when there is an extract on the grain boundary, whether its strength is stronger or weaker than that of the matrix, it is the cause of cracking; The segregation of inclusions on grain boundaries is also the cause of fracture; In addition, fatigue fracture can occur even under alternating loads that are much smaller than the yield limit.

In the process of low-stress brittle fracture that occurs in high-strength metal materials, the material structure is far from homogeneous and isotropic. When the means are used reasonably to clean up the rusty pipe fittings, the pipe fittings are guaranteed to serve the production for a long time and create more production benefits. Alloy pipes should be finished with a finished surface whenever possible.

In addition, the surface cleanliness of the 16mn seamless steel pipe is also very important, and the final cleaning after passivation should be carried out carefully, because the residual acid promotes the cathodic reaction and ruptures the film layer, so that the 16mn seamless steel pipe is activated, and the corrosion resistance is drastically reduced, thereby reducing the cracks in the structure of the 16mn seamless steel pipe. Only by being careful can we avoid mistakes.

No matter what kind of steel it is, cracking is inseparable from the influence of the composition, structure, and process of the material. Poor billet quality is also easy to crack, such as the quality of the ingot, the ingot contains bubbles and is easy to crack. The internal or external cracks of the steel pipe may be caused by the five harmful elements in terms of chemical composition, and if the process is overheated or overburned, it will cause cracking, cracks caused by low-temperature rolling, hot brittle cracks, and so on.

16mn is low-alloy high-strength structural steel: carbon content, adding the main alloying elements manganese, silicon, vanadium, niobium and titanium; Its total alloy content <3%. According to the intensity, it is divided into 4 levels, such as 450MPa.

Mainly Q295, Q345, Q390, Q420, Q460. "Q" is the Chinese Pinyin capital prefix of the word "yield", followed by the number is the minimum yield point (s) value of the grade, and the symbol followed by the steel impurity elements (sulfur, phosphorus) from high to low and accompanied by the change of carbon and manganese elements are divided into A, B, C, D and so on. Among them, grade A and B steel are usually called 16MN.

In January 2002, Jiangsu Yixing Beihai head **** following the use of CR-Mo steel to produce stainless steel head for microelectronics, and the production of stainless steel head for nuclear energy, which is the first time that stainless steel has been used in nuclear energy.

On July 6, 2005, China's first self-made 3,000-ton stainless steel chemical tanker "Ninghua 417" with completely independent intellectual property rights was sent to the Yangtze River.

In May 2006, Changchun Rail Passenger Car Co., Ltd. **** assembly plant in the new line 5 new car prototype. This 6-car subway bus is the first unpainted stainless steel urban rail bus in China.

On November 22, 2006, Jiangnan Heavy Industry Co., Ltd. held a signing ceremony for the manufacturing contract of 7,500 cubic meters of LNG ship C-type independent cabin --- LNG stainless steel tank in Shanghai and TGE Gas Engineering Co., Ltd. of Germany. This is the first LNG stainless steel liquid tank manufactured by China.

At the beginning of 2007, China's National Development and Reform Commission Industry Department reported that China's stainless steel output exceeded 5 million tons in 2006, ranking first in the world for the first time.

At the beginning of 2007, TISCO Super Duplex Stainless Steel S32750 medium plate development was successful. So far, TISCO has become the first enterprise in China to successfully produce super duplex stainless steel, and has filled the gap of this product in China.

In January 2007, Baosteel Stainless Steel Branch launched the first version of the stainless steel user service manual, which was the first time in the domestic stainless steel enterprises.

In March 2007, Wenzhou Jinzhou Special Steel successfully developed 0Cr15Mn12Ni2Cu austenitic stainless steel, and produced qualified stainless steel pipes, which is the first low-nickel austenitic stainless steel seamless steel pipes launched in China.

On March 28, 2007, the delivery ceremony of 51 stainless steel tank insulated vehicles exported to Syria for the first time by Kazakhstan Jiancheng Northern Special Vehicle Company was held.

The above is just a simple review, and it is not possible to list all the innovations in China's 16 manganese steel pipe industry, but it can be seen that the leopard in the pipe can be seen. We are enough to see the rapid progress of China's stainless steel industry, and we have more reason and confidence to believe that China's stainless steel industry will have a brilliant future.