inconel725 ingredients | performance | yield | tensile strength
inconel725 (UNS N07725)Alloy725 nickel-based high-temperature alloy
Introduction:
Inconel 725 alloy is a nickel-chromium-molybdenum-niobium alloy with excellent corrosion resistance. After aging heat treatment, it can greatly increase the strength of the alloy and greatly improve the ductility and tensile strength of the alloy. The alloy also has strong resistance to stress corrosion.
chemical composition:
C(%):≤0.03
Si(%):≤0.20
Mn(%):≤0.35
Cr(%):19.0～22.
Ni(%):55.0～59.0
Mo(%):7.00～9.50
Co(%):-
W(%):-
Al(%):≤0.35
Cu(%):-
Ti(%):1.0～1.7
Fe(%): balance
Others (%): Nb/Ta 2.75～4.00, P≤0.015, S≤0.01
The minimum mechanical properties of the alloy at room temperature are:
Alloy state solution treatment
Tensile strength 568 Rm N/mm2
Yield strength 313 Rp0.2 N/mm2
Elongation 35 A5 %
Brinell hardness 35 HB
Physical properties:
Density 8.2 g/cm3
Melting point 1260-1340 ℃.
Alloys have the following properties:
This alloy is a nickel-chromium-molybdenum-niobium alloy with excellent corrosion resistance. After aging heat treatment, it can greatly increase the strength of the alloy and greatly improve the ductility and tensile strength of the alloy. The alloy also has strong resistance to stress corrosion.
Application fields of Inconel 725:
Used for pipe fittings, joints and bearings in acid-resistant equipment. It is also widely used in marine ship equipment.
Introduction to ironmaking process
The iron-making process is essentially the process of reducing iron from its natural form - iron-containing compounds such as ores. Iron-making methods mainly include blast furnace method, direct reduction method, smelting reduction method, etc. The principle is that the ore obtains reduced pig iron through physical and chemical reactions in a specific atmosphere (reducing substances CO, H2, C; suitable temperature, etc.). Except for a small part of pig iron used in casting, most of it is used as raw material for steelmaking.
1. The smelting principle of blast furnace ironmaking (the most widely used)
(1) Raw materials for blast furnace smelting
It is mainly composed of three parts: iron ore, fuel (coke) and flux (limestone).
Usually, smelting 1 ton of pig iron requires 1.5-2.0 tons of iron ore, 0.4-0.6 tons of coke, 0.2-0.4 tons of flux, and a total of 2-3 tons of raw materials. In order to ensure the continuity of blast furnace production, a sufficient supply of raw materials is required.
(2) Process flow
Although the principle of smelting pig iron is the same, the process flow is also different due to different methods and different smelting equipment. They are briefly introduced below.
Blast furnace production is continuous. A generation of blast furnace (from opening to overhaul and shutdown is a generation) can produce continuously for several to more than ten years. During production, iron ore, coke, and flux are continuously loaded from the top of the furnace (generally the top is composed of materials and hoppers, and modern blast furnaces are bell valve tops and bellless tops), and are blown from the tuyere at the lower part of the blast furnace. Input hot air (1000~1300℃) and inject fuel such as oil, coal or natural gas. The iron ore loaded into the blast furnace is mainly a compound of iron and oxygen. At high temperatures, the coke neutralizes the carbon in the injection material and the carbon monoxide generated by the combustion of the carbon takes away the oxygen in the iron ore to obtain iron. This process is called reduction. Iron ore produces pig iron through a reduction reaction, and molten iron is released from the taphole. The gangue in the iron ore, coke and ash in the injection material combine with fluxes such as limestone added into the furnace to form slag, which is discharged from the taphole and slag outlet respectively. The gas is exported from the top of the furnace, and after dust removal, it is used as industrial gas. Modern blast furnaces can also take advantage of the high pressure on the top of the furnace and use part of the gas exported to generate electricity.
Pig iron is a product of a blast furnace (referring to the smelting of pig iron in a blast furnace), and the products of a blast furnace are not only pig iron, but also ferromanganese, etc., which are ferroalloy products. Ferromanganese blast furnace does not participate in the calculation of various indicators of iron-making blast furnaces. The blast furnace ironmaking process also produces by-products such as slag, slag wool and blast furnace gas.
Characteristics of blast furnace ironmaking: Large scale. Whether in other countries in the world or in China, the volume of blast furnaces is constantly expanding. For example, the blast furnace of Baosteel in my country is 4063m3, with a daily production of more than tons of iron, more than 4,000 tons of slag, and a daily consumption of more than 4,000 tons of coke.
At present, domestic single pig iron manufacturers have a blast furnace volume of about 500 m3 or more, but most of them are still between 100-300 m3. There are even small blast furnaces of less than 100 m3 with high energy consumption and high pollution. The quality of their products is uneven and the announcements are scattered. , does not have the expected scale, let alone be compared with international steel plants. Xie Qihua, president of China Baosteel Group, revealed that the Chinese government has ordered small steel plants with a blast furnace capacity of less than 200m3 to close before the end of 2007. Steel plants using outdated technology will be phased out by 2010. If steel prices fall, this deadline will still remain. It is possible to advance.
2. What is a rolling mill?
A rolling mill is a device that implements the metal rolling process. It generally refers to the equipment that completes the entire process of rolled product production, including main equipment, auxiliary equipment, lifting and transportation equipment, and ancillary equipment. But generally speaking, the rolling mill often refers only to the main equipment.
3. Development history of rolling mill
It is said that rolling mills existed in Europe in the 14th century, but what is recorded is the sketch of a rolling mill designed by Italian Leonardo da Vinci in 1480. In 1553, Frenchman Brulier rolled out gold and silver plates to make coins. Since then, rolling mills have appeared in Spain, Belgium and the United Kingdom. The rolling mill designed in 1728 for the production of round bars was a rolling mill designed in England for the production of round bars. The United Kingdom had a serial small rolling mill in 1766. In the mid-19th century, the first reversible plate rolling mill was put into production in the United Kingdom and rolled out ship iron plates. In 1848, Germany invented the universal rolling mill. In 1853, the United States began to use a three-roller profile rolling mill and mechanized it with a lifting table driven by a steam engine. Then came the Lauter mill in the United States. The first continuous rolling mill was built in 1859. The universal profile rolling mill appeared in 1872; in the early 20th century, a semi-continuous strip rolling mill was developed, consisting of two three-roll roughing mills and five four-high finishing mills.
China began to use rolling mills in 1871 at the Iron Drawing Plant (steel rolling mill) affiliated to the Fuzhou Shipping Bureau; it rolled iron plates with a thickness of less than 15 mm, and square and round steel with a thickness of 6 to 120 mm. In 1890, the Hanyang Iron Works of Hanyeping Company was equipped with a two-stand horizontal two-stand 2450mm two-high medium plate rolling mill driven by a steam engine, a three-stand horizontal two-high rail beam mill driven by a steam engine, and a 350/300mm small rolling mill. With the development of the metallurgical industry, there are now many types of rolling mills.
4. The main equipment of the rolling mill includes the working stand and transmission device.
(1) Working base
It consists of rollers, roller bearings, machine frames, rail seats, roll adjustment devices, upper roll balancing devices and roll changing devices.
a. Roller: It is a component that plastically deforms metal.
b. Roller bearing: supports the roller and keeps the roller in a fixed position in the frame. The working load of the roll bearing is heavy and changes greatly, so the bearing friction coefficient is required to be small, have sufficient strength and stiffness, and be easy to replace the roll. Different rolling mills use different types of roll bearings. Rolling bearings have high rigidity and small friction coefficient, but have small pressure-bearing capacity and large external dimensions. They are mostly used for work rolls of plate and strip mills. There are two types of sliding bearings: semi-dry friction and liquid friction. Semi-dry friction roller bearings are mainly bakelite, copper tile, and nylon tile bearings. They are relatively cheap and are mostly used in profile rolling mills and blanking machines. There are three types of liquid friction bearings: dynamic pressure, static pressure and static-dynamic pressure. The advantages are that the friction coefficient is relatively small, the pressure-bearing capacity is large, the operating speed is high, and the rigidity is good. The disadvantage is that the oil film thickness changes with speed. Liquid friction bearings are mostly used in back-up rollers of plate and strip mills and other high-speed rolling mills.
c. Rolling mill frame: It consists of two "archways" to install the roll chock and roll adjustment device. It must have sufficient strength and steel to withstand the rolling force. There are two main types of racks: closed and open. The closed frame is an integral frame with high strength and rigidity. It is mainly used for blooming mills and plate and strip mills with large rolling forces. The open frame consists of two parts: the frame body and the upper cover, which facilitates roll change. It is mainly used in horizontal profile rolling mills. In addition, there are mills without arches.
d. Rolling mill rail seat: used to install the machine frame and fixed on the foundation, also called footing plate. It can withstand the gravity and tilting moment of the work base while ensuring the accuracy of the installation dimensions of the work base.
e. Roller adjustment device: used to adjust the roll gap so that the rolled piece reaches the required cross-sectional size. The upper roller adjustment device is also called the "press-down device" and has three types: manual, electric and hydraulic. Manual pressing devices are mostly used in profile rolling mills and small rolling mills. The electric press-down device includes components such as a motor, a reducer, a brake, a press-down screw, a press-down nut, a press-down position indicator, a spherical pad and a pressure gauge; its transmission efficiency is low, the rotational inertia of the moving part is large, and the reaction The speed is slow and the adjustment accuracy is low. Since the 1970s, after the plate and strip rolling mill adopted the AGC (automatic thickness control) system, hydraulic reduction devices have been used in new strip cold and hot rolling mills and thick plate rolling mills, which have the advantages of small plate thickness deviation and high product qualification rate. .
f. Upper roll balancing device: a device used to lift the upper roll and prevent the rolled piece from being impacted when entering and exiting the roll. The forms are: spring type, mostly used in profile rolling mills; hammer type, often used in blooming mills with large roll movement; hydraulic type, mostly used in four-high plate and strip mills.
g. In order to improve the operation rate, the rolling mill is required to change rolls quickly and conveniently. There are four roller changing methods: C-shaped hook type, sleeve type, trolley type and whole frame roller changing type. The first two methods are used to change the rolls with the assistance of a crane, while two sets of frames are required for roll change in the entire frame. This method is mostly used in small rolling mills. Cart roll changing is suitable for large rolling mills and is conducive to automation. At present, rolling mills adopt fast automatic roll changing devices, and it only takes 5 to 8 minutes to change a roll.
(2) Transmission device
It is composed of electric motor, reducer, gear seat and connecting shaft. The gear seat distributes the transmission torque to two or several rollers.
(3) Auxiliary equipment
It includes equipment for a series of auxiliary processes in the rolling process. Such as raw material preparation, heating, steel turning, shearing, straightening, cooling, flaw detection, heat treatment, pickling and other equipment.
(4) Lifting and transportation equipment
Cranes, transport trucks, rollers and transfer machines, etc.
(5) Ancillary equipment
There are equipment for power supply, power distribution, roll grinding, lubrication, water supply, drainage, fuel supply, compressed air, hydraulic pressure, iron oxide scale removal, machine repair, electrical repair, acid discharge, oil, water, acid recovery, and environmental protection.
5. Naming of rolling mill
It is named according to the rolling variety, rolling mill type and nominal size. The principle of "nominal size" for profile rolling mills is named after the pitch circle diameter of the gear seat; the roughing mill is named after the nominal diameter of the roll; the plate and strip mill is named after the length of the work roll body; the steel pipe rolling mill is named after the maximum production capacity Named according to pipe diameter. Sometimes it is also named after the inventor of the rolling mill (such as Sendzimir Mill).
6. Selection of rolling mill
The type and size of the finished product or semi-finished product rolling mill is selected according to the product variety, specifications, quality and output requirements, and the necessary auxiliary, lifting and transportation and ancillary equipment are equipped, and then the final selection is balanced based on the requirements of various factors .
7. Rolling mill power facilities
In 1590, Britain began to use water turbines to drag rollers. Until 1790, there were still water turbines equipped with stone flywheels to drive four-roller steel plate rolling mills. In 1798 England began to use steam engines to drag rolling mills. Modern rolling mills are driven by DC or AC motors, either individually or in groups through gears.
8. Classification of rolling mills
Rolling mills can be classified according to the arrangement and number of rolls, the arrangement of the frames, and the products produced.
9. Development of rolling mill
The development trend of modern rolling mills is continuity, automation, specialization, high product quality and low consumption. Since the 1960s, great progress has been made in the design, research and manufacturing of rolling mills, which has improved the performance of hot and cold strip rolling mills, thick plate rolling mills, high-speed wire rod rolling mills, H-section rolling mills and continuous pipe rolling mills, and the emergence of rolling mills. It has a series of advanced equipment such as a wire rod rolling mill with a production speed of up to 115 meters per second, a fully continuous strip cold rolling mill, a 5500 mm wide and thick plate rolling mill and a continuous H-beam rolling mill. The unit weight of raw materials used in rolling mills has increased, hydraulic AGC, flatness control, electronic calculator process control and testing methods have become more and more perfect, and rolling varieties have continued to expand. Some new rolling methods suitable for continuous casting and rolling, controlled rolling, as well as rolling mills with various special structures to adapt to new product quality requirements and improve economic efficiency are under development.
