Graduation design (thesis)
、
6mm thick 0Cr 18Ni9 steel plate adopts covered electrode arc welding.
Welding procedure qualification (drawing) is based on.
Special welding technology and its automation
class number
surname
teacher
June 5(th), 2008
abstract
Steel is an indispensable material in our modern society and can be regarded as a symbol of a country's industrialization level. The higher the output of steel, the higher the industrialization level of this country. Stainless steel is a very important steel. Stainless steel has been used more and more in all walks of life because of its special properties and mechanical properties. Austenitic stainless steel is one of the most important stainless steels. In developed countries, the annual consumption of stainless steel is 70%, which has reached about 65% in China. Therefore, it is more and more important for me to develop and use austenitic stainless steel.
0cr 18ni9 is austenitic stainless steel, and this topic I am doing is to discuss the performance of 0cr 18ni9 in the manufacture of low-temperature storage tanks. The cryogenic storage tank is used to store cryogenic liquids, such as liquid nitrogen, liquid argon and liquid carbon dioxide. The special properties of liquid medium determine that the manufacturing materials need special properties, such as austenitic stainless steel 0cr 18ni9. Cryogenic storage tanks have been widely used in our daily life and production, so it is more and more important to discuss 0cr 18ni9. This paper will mainly introduce the welding performance, mechanical properties, service performance and welding technology of 0cr 18ni9 in the manufacture of low-temperature pressure vessels.
This paper will discuss the performance of 0gr 18ni9 in low temperature pressure vessel through a weldability test. My experiment is that the horizontal butt welding method of two pieces of 0cr150× 300mm is manual arc welding. According to this test, a complete welding procedure evaluation is carried out, and corresponding nondestructive inspection and mechanical property inspection are carried out according to the evaluation requirements, so as to judge the performance of 0cr 18ni9.
Key words:
Welding performance, mechanical performance and service performance, welding process
abstract
Steel is an indispensable material in our modern society, and it can be regarded as a symbol of the level of industrialized countries. The higher the steel output representing this country, the higher the level of industrialization. Stainless steel is a very important kind. Because of its special performance and mechanical properties, it has been used more and more in all walks of life. Austenitic stainless steel is a very important kind of stainless steel. In developed countries, 70% of the annual consumption of stainless steel is stainless steel, and it has reached about 65% in China. Therefore, the development and use of austenitic stainless steel has become more and more important for my industry.
0cr 18ni9 is austenitic stainless steel, and what I have done on this subject is the performance of 0 cr 18ni9 in low-temperature storage tank manufacturers. Cryogenic storage tank is a container for storing liquid CO2 and other cryogenic liquids. The special properties of liquid medium determine that materials need special properties, and austenitic stainless steel 0 cr 18ni9 has such properties. Low-temperature storage tanks have been widely used in current life and production, so 0 cr 18ni9 steel is an indispensable material in our modern society, which can be regarded as a symbol of the level of industrialized countries. The higher the steel output representing this country, the higher the level of industrialization. Stainless steel is a very important kind. Because of its special performance and mechanical properties, it has been used more and more in all walks of life. Austenitic stainless steel is a very important kind of stainless steel. In developed countries, 70% of the annual consumption of stainless steel is stainless steel, and it has reached about 65% in China. Therefore, the development and use of austenitic stainless steel has become more and more important for my industry.
0cr 18ni9 is austenitic stainless steel, and what I have done on this subject is the performance of 0 cr 18ni9 in low-temperature storage tank manufacturers. Cryogenic storage tank is a container for storing liquid CO2 and other cryogenic liquids. The special properties of liquid medium determine that materials need special properties, and austenitic stainless steel 0 cr 18ni9 has such properties. Low-temperature storage tanks have been widely used in current life and production, so the research on 0 cr 18ni9 becomes more and more important. In this paper, I will focus on the welding performance, mechanical performance, service performance and welding technology we have elaborated in the manufacture of cold 0 cr 18ni9 pressure vessel.
In this paper, the performance of 0 gr 18ni9 in low temperature pressure vessel will be discussed through welding test. This is my test specification, which is applicable to 6×150× 300mm20cr18ni9. The butt welding method is the level of manual arc welding. For the pilots who have completed the welding procedure qualification, the corresponding mechanical properties shall be nondestructive tested and inspected according to the design requirements, so as to determine the properties of 0 cr 18ni9.
Ming is increasingly important. In this paper, I will focus on the welding performance, mechanical performance, service performance and welding process specified in the manufacture of cold 0 cr 18ni9 pressure vessel.
In this paper, the performance of 0 gr 18ni9 in low temperature pressure vessel will be discussed through welding test. This is my test specification, which is applicable to 6×150× 300mm20cr18ni9. The butt welding method is the level of manual arc welding. For the pilots who have completed the welding procedure qualification, the corresponding mechanical properties shall be nondestructive tested and inspected according to the design requirements, so as to determine the properties of 0 cr 18ni9.
Key words:
Welding properties, mechanical properties, welding process operability
catalogue
1 Introduction
2 background of the project.
3 material introduction
Welding of 4cr 18ni9
Weldability analysis.
4.2cr18ni9 welding process ............................................................
4.2. 1 0Cr 18Ni9 welding process thought analysis ..................................
4. 2. 2 0cr 18ni 9 Welding Process Application ..................................................
5 conclusion ....................................................................
6 references
7. Thank you.
foreword
Machinery industry is an industry that provides machinery and equipment for all industries, agriculture, national defense and transportation. In the process of realizing China's four modernizations, we must implement the spirit of the party's general line and constantly solve the problems of designing and manufacturing machinery and equipment with high efficiency, long life, light weight, small volume, large capacity and low cost. In order to accomplish this glorious and arduous task and make the mechanical design and manufacturing capability surpass the world level in a short time, we should not only solve the scientific problems of design, manufacturing and use. The material problem in mechanical manufacturing is partly the composition and quality of the metal material itself, and the other part is whether the material selection is appropriate and whether the maximum potential of the material is exerted in the processing technology. Therefore, while improving the output and quality of metal materials, we should also improve and give full play to the various properties of materials, fully tap the potential, and be practical and economical. Only in this way can we achieve the goal of building socialism faster, better and more economically.
Before the liberation of our country, the science and production of alloy steel were almost blank. After liberation, the development speed of China machinery industry is unprecedented in the world. In recent 20~30 years, the appearance and wide use of stainless steel have promoted the progress of stainless steel industry. Stainless steel is widely used in aerospace, shipbuilding, military industry, chemical industry, energy and other aspects, as well as the decoration of daily furniture, buildings and vehicles, because of its excellent corrosion resistance, wear resistance, strong toughness, good machinability, exquisite appearance and non-toxicity.
Stainless steel and corrosion-resistant and heat-resistant alloys are difficult to weld because of their complex and changeable structures. The performance of welded joints is directly related to the safety of equipment. A lot of research work has been done on the welding of stainless steel and corrosion-resistant and heat-resistant alloy at home and abroad. The research on its weldability, welding materials and welding technology is almost synchronous with the research on base metal, which promotes the development of stainless steel and corrosion-resistant and heat-resistant alloys. Although there are many research results and documents in this field, there are few systematic ones. In practical work, some welding technicians and welders don't know much about the welding knowledge of stainless steel and corrosion-resistant and heat-resistant alloys, and some even copy the technology and methods of low-alloy steel directly. Although China's efforts in stainless steel in recent years are obvious to all, compared with the advanced countries in the world, there is still a big gap. In order to make up this gap as soon as possible, we need modern scientific and technological talents, and we need to pay more. With the rapid development of socialist revolution and modernization and people's demand for high-quality life, stainless steel and its related technical science will continue to develop and improve.
In the world, 45% of steel bar connections are completed by welding, and manual arc welding is our life.
As an indispensable part, I use more and more austenitic stainless steel at present, so the research on austenitic stainless steel welding has become more and more urgent. This paper studies the welding of austenitic stainless steel from the perspective of manual arc welding. Based on the mechanical properties and chemical composition of materials, this paper discusses the weldability of austenitic stainless steel through the analysis of weldability. The most intuitive performance of austenitic stainless steel welding performance is the welding process knowledge manual. We reflect the welding performance of austenitic stainless steel by compiling welding process instructions.
Project background
Austenitic stainless steel is used in more and more places in modern society because of its special weldability. Now austenitic stainless steel is also a direction of our development and research. In the future, more and more experts will pay attention to the development and research of austenitic stainless steel, and our understanding of austenitic stainless steel welding should also be paid more and more attention.
There are many ways to weld austenitic stainless steel. Submerged arc welding is mainly used for welding austenitic stainless steel of medium and heavy plate in China. Manual arc welding is widely used in the production of austenitic stainless steel structures because of its flexible and convenient operation and low equipment investment. This is also a typical traditional welding method. Stainless steel covered electrode, which plays a key role in manual arc welding, has made the following progress after years of efforts by welders in China:
(1) variety
It basically covers various conventional stainless steel grades such as 308, 3 16, 309, 347 and 3 17. , usually including acids.
Sex and alkaline slag system. 308L, 3 16L, 309L and other ultra-low C stainless steels are also produced in covered electrode, so the varieties can basically meet the needs of industrial departments.
⑵ Quality
For the traditional stainless steel covered electrode, the covered electrode redness, arc stability, splash size, weld formation,
The quality of domestic stainless steel covered electrode varies in color, ripple fineness, all-position welding adaptability, welder's welding comfort, welding mechanical properties and corrosion resistance. But it can basically meet the requirements of domestic users. For some special varieties such as 3 10MoL, 347L and 309L, there are still many factories willing to use imported welding materials. This also shows that the overall quality of stainless steel in covered electrode is still far behind that of foreign countries, and there is a big gap in some special varieties.
Submerged arc welding of stainless steel is mostly used for circumferential seam and longitudinal seam of stainless steel cylinder. Usually, X-groove is made by welding the inner weld first, and then grinding it with reverse grinding wheel (even air gouging). Then weld the front face, and the current process is required and recognized in the standard. The existing problems are:
(1) has great damage to the base material, which is not conducive to corrosion performance and affects the appearance.
② Submerged arc welding stainless steel welding wires have few varieties and poor quality. 260 and 43 1 and 350 fluxes often leave transverse slag in the weld after welding. Welders need grinding wheels.
③ Therefore, submerged arc welding of stainless steel has low efficiency, high cost and rough quality.
(3), CO2 stainless steel flux-cored wire arc welding
CO2 gas shielded stainless steel flux-cored wire has been used to weld stainless steel for nearly twenty or thirty years. This method uses conventional CO2 welding machine or MIG welding machine, and adopts 100%CO2 or 80%Ar+20%O2 as shielding gas, which is similar to that of common structural steel solid wire welding and can obtain beautiful weld. Among these three welding methods, CO2 shielded stainless steel flux-cored wire tends to replace the first two welding methods. See table 1 for the comparison of these three welding methods.
Comparison of stainless steel manual arc welding, MIG solid wire welding and CO2 gas shielded stainless steel flux-cored wire arc welding.
Comparison project stainless steel manual arc welding MIG solid wire CO2 stainless steel flux-cored wire
Low efficiency and high efficiency
High cost, high cost and low cost
Good operation technology and better performance.
The weld is beautiful, higher and better.
Good welding performance.
All-position adaptability is generally good.
How many kinds of welding wires are there?
There are many technical requirements for welders.
From the above data analysis, manual arc welding will gradually be replaced by CO2 gas shielded welding, but the application of manual arc welding is still very common at this stage!
Austenitic stainless steel has many ideal properties required by building and chemical equipment materials, which can be said to be unique among metals, and its development is still going on. In order to improve the performance of stainless steel in traditional applications, the existing types have been improved, and new stainless steel is being developed to meet the strict requirements of advanced building applications. Due to the continuous improvement of production efficiency and quality, stainless steel has become one of the most cost-effective materials chosen by architects.
From the above analysis, it can be seen that stainless steel has good weldability and is widely used. This kind of stainless steel welding technology is becoming more and more mature, but at this stage, manual arc welding is the most widely used one. In this context, I choose to do such a project, which is not only conducive to understanding the current situation of 0Cr 18Ni9 welding, but also conducive to understanding the development direction of 0Cr 18Ni9 welding.
Weldability analysis of OCr 18Ni
What is solderability? GB/T3375-94 "Welding Terminology" stipulates: "The ability of materials to be welded into components according to the specified design requirements under limited construction conditions, and meet the intended use requirements". It includes two aspects: first, the welded components meet the design requirements; The second is to meet the predetermined conditions of use and be able to run safely.
According to the different points discussed, solderability can be divided into:
(1) process weldability
(2) the use of weldability
The main factors affecting solderability are as follows:
(1) material coefficient
(2) Welding method
(3) Component type
(4) Use requirements
The weldability of metal is closely related to material composition, welding method, component type and application requirements, and the weldability cannot be evaluated simply from the performance of the material itself without these factors. From the above analysis, it can be seen that it is difficult to find a technical index that can summarize the weldability, and only by integrating various factors can the weldability be analyzed.
When analyzing the weldability of metal, we can judge it according to the carbon equivalent, the chemical properties of the material and the physical properties of the material. If the requirements are very accurate, we can also judge it through the weldability test. We will judge the welding performance of 0cr 18ni9 from this aspect:
Welding requirements of 1 and 0Cr 18Ni9
1)0Cr 18Ni9 belongs to austenitic stainless steel, and its structure is austenite (a) plus 3-5% ferrite (f). It has good plasticity and high and low temperature properties. Under the action of welding thermal cycle, it mainly shows the following basic requirements:
(1) Using less linear energy input, reducing the range of heat affected zone and accelerating the cooling rate of weld and heat affected zone is beneficial to stainless steel welding.
② When welding with 0Cr 18Ni9, the thermal conductivity is small, and there is an overheating zone, which is also easy to cause grain growth in the heat affected zone. If the weld stays at high temperature for too long, Cr and C will form compounds at high temperature, and a chromium-poor layer will be formed at high temperature, which will also lead to the intensification of the dendrite tendency of the weld. Therefore, it is required to choose the welding method with less linear energy input as far as possible.
(3) Because of the small thermal conductivity and large linear expansion coefficient, welding is easy to produce large deformation in the free welding state. Welding deformation can be reduced to some extent by adopting the welding method with concentrated energy and narrow heat affected zone.
2) 2) The carbon content of 0Cr18Ni9 is very small, which belongs to high alloy steel, and the estimation of its welding performance by carbon equivalent method is not very accurate. So we don't use carbon equivalent to analyze its weldability.
3) 0cr 18ni9 belongs to austenitic stainless steel, which has high deformability, can't be hardened, low carbon content and good overall weldability. However, due to the low thermal conductivity, large thermal expansion coefficient, uneven temperature distribution and large shrinkage during local heating, the internal stress of the joint will be high during welding. Pay attention to this problem when welding, try to avoid or reduce the occurrence of uneven heating, and the welding speed should be appropriately fast.
Above, we analyzed the weldability of 0cr 18ni9 from two aspects of chemical composition and physical properties, but it is not accurate enough to judge the weldability according to these. We need to accurately judge its weldability, which must be done by weldability test. There are many in weldability test, so I will use the oblique Y-groove welding crack test method here.
The plate size is 6×150× 200mm.
The welding method is manual arc welding.
Welding material model A 132, specification? 3.2 mm
The shape of the groove is inclined y-shaped.
The welding parameters are: current: 90- 120A, voltage: 20-24V, speed: 15-20cm/min.
The test diagram of inclined Y-groove crack is as follows:
Welding samples need to be aged for 48 hours before crack detection and dissection. Cracks can be divided into three forms: surface cracks, heel cracks and cross-section cracks. First, visually inspect the cracks on the weld surface with a magnifying glass or fluorescent powder, and then mechanically cut six transverse specimens with the same length to inspect the five cracks. Generally, the crack rate is used as the evaluation standard.
Root crack rate = ∑ lr/l× 100%
Surface crack rate = ∑ LF/L× 100%
End cracking rate = ∑ h/5h× 100%
The total length of the test weld is 80mm, the total length of our welding crack is 9.8 mm, and the crack rate of the specimen is less than 20%. Therefore, if the requirements are followed in actual production, there will be no cracks, and the welding performance of this steel is acceptable.
To sum up, 0cr 18ni9 steel has good weldability. If we follow the standard in production, we should be able to produce qualified products with acceptable performance.
Welding technology of 0Cr 18Ni9
Table I- 1
Welding procedure qualification instruction (task book)
Compilation instruction number HJ05 1 1-29.
Reasons for inspection and evaluation
Approval completion date
Review on Acceptance Organization of Calibration Standard JB4708-2000
Schematic diagram of parent metal thickness, mm size and mm joint form
0cr 18ni 9 6mm 6 * 150 * 300
0cr 18ni 9 6mm 6 * 150 * 300
Welding position 1G welding direction correct welding method
Protective gas/interlayer temperature/
Preheating/
Mechanized degree manual welding
Post-weld heat treatment/
Post heat treatment/
Gasket material/specification/
Root cleaning method/
Layer welding
Methods welding material model/brand welding material
Specification current type
And polarity current.
voltage
(5) Welding speed
(cm/min) heat transfer
Into (kilojoule/cm) tungsten electrode
Diameter nozzle
diameter
1 SMAW A 102 3.2mm reverse 90-1018.5 ~ 2015 ~18 6.67//
2 SMAW A 102 3.2mm reverse connection100-120 20 ~ 2218 ~ 20 6.7//
Inspection items, evaluation indicators and sample quantity
Inspection standard evaluation index of inspection items Sample number of inspection standard evaluation index of inspection items
Visual inspection GB 150 JB4708 Tensile test GB/T228 JB4708 2
not have
harm
check
Radiation measurement (RT) JB4730 JB4708 Bending test Surface bending GB/T
232
JB4708 2
Ultrasonic (UT)// Back bending JB4708 2
Permeability (PT)// Transverse bending//
Magnetic powder (MT)// impact
Test weld GB/T
229 JB4708 /
Weld chemical composition//heat affected zone JB4708/
golden
Macro stage//Corrosion test///
Microscope//Hardness test///
Description of welding procedure qualification
Item code: HJ05 1 1-29
Name: Manual arc welding procedure qualification (stretching) of 6mm thick 0Cr 18Ni9 steel plate.
Compile:
Audit:
Ratification:
Table 1 -2
Guide to welding technology evaluation
Changzhou Braun Cryogenic Co., Ltd.
Welding procedure instructionNo. HJ05 1 1-29 Date June 2008 Welding procedure qualification reportNo. HJ0511.
Mechanization degree of welding method covered electrode arc welding (manual, semi-automatic and automatic) manual.
Welded joint:
Blunt-edged v-groove
Gasket (material and specification)/
Others/
Schematic diagram: (joint form, groove form and size, covered electrode, weld arrangement and sequence)
Parent material: Class number VII, group number VII- 1 and class number VII, group number VII- 1 are welded together.
Standard number/Stilno. /Weld with standard number/Stilno. /
Thickness range: parent metal: butt weld 1.5~ 12 fillet weld is not limited.
Range of pipe diameter and wall thickness: butt weld 1.5~ 12 fillet weld is not limited.
Weld metal thickness range: butt weld 12 fillet weld is not limited.
Others:
Welding materials:
Welding material category covered electrode
Welding material standard GB/T983
Filled metal size 3.2mm.
Welding material model E307- 16
Welding material brand A 132
Others/
Chemical composition of corrosion-resistant surfacing metal (%)
C Si Mn P S Cr Ni Mo V Ti Nb