Design and construction of ECAR machine in order to investigate process effects on low carbon steel sheets

Dissertation for M.Sc)) in the field of mechanics

Manufacturing and Production Orientation

Abstract

In the present research, under the title of designing and manufacturing the ECAR device in order to investigate the effects of the process on carbon steel sheets, we aimed to achieve a method to increase the strength and resistance of metal alloys. The desired research was carried out in the research workshop of Islamic Azad University, Jaseb Branch. After the design and construction of the ECAR machine, the metal sheets prepared according to the STDA standard were passed through the mold of the machine, the results were reported as follows that the ECAR method was able to increase the yield strength, final strength and hardness in different passes by reducing the length increase and changes in the grain size of the metal.

Key words:

ECAR machine, low carbon steel, pass, yield strength, ultimate hardness in the field of material science. The mechanical properties of nanocrystalline materials or sub-micron domains have been of great interest due to their unusually high strength and superplastic properties at high strain rates and low temperatures, impact properties, good abrasion resistance and high fatigue limit.

Plastic deformation methods must meet some requirements. These requirements are:

1- It is important to obtain an ultra-fine grain structure with a grain boundary with a large angle; because only in this way can a qualitative change in the properties of the material occur.

2- The formation of a uniform nanostructure in the entire volume of the sample is necessary in order to create stable properties.

3- At the same time that the samples are exposed to severe plastic deformation, they should not have any mechanical damage or cracks.

Common methods of severe plastic deformation such as Rolling, forging, extrusion, and deep drawing cannot meet these requirements.

Currently, most of the results obtained are related to the use of two SPD methods: torsional straining under high pressure and pressing in a flat angular channel. Recently, a process called rolling in equal-angle channels, which is one of the alternative methods of pressing in equal-angle channels, has been invented, which has been able to meet the requirements of SPD methods well.

In this chapter, an overview of the types of extreme plastic deformation methods is first mentioned, and then the researches and researches carried out on the rolling process in equal channels

1-2- Statement of the problem

One ??of the objectives of this research is to design and build a rolling machine in ECAR equal angled channels for the purpose of laboratory studies of the effective variables in the process and also to provide appropriate solutions to optimize the method of conducting the tests.

1-3- Research objectives

In recent years, the investigation of production methods and mechanical properties of materials with very fine grain size has been the subject of many researches in the field of materials science and related sciences. So far, various methods for producing materials with very fine grain size have been presented and extensive research has been done on them. The production methods of these materials can be divided into two general groups. The first method, which is introduced under the bottom-up procedure, includes processes such as mechanical alloying, chemical vapor deposition, and rapid freezing. These processes are widely used to produce large quantities of very fine powders (around 10-15 nm). But the main problem of these processes is to produce a final product by pressing these powders.So far, various methods have been proposed to solve these problems, but research is still ongoing to find a suitable method for pressing powders and producing the final product. The second method for producing this type of material, which is known as the top-down procedure, includes processes that reduce the grain size to the nanometer scale by applying severe plastic strains to metal materials. This method includes processes such as high pressure torsional deformation (HPT), equal angle channel deformation (ECAP), equal pressure and extrusion process (CEC) and cumulative rolling process (ARB). In addition to the mentioned processes, today processes such as deformation in ECAP by rolling (ECAR), corrugation and successive smoothing process (RCS) and cyclic forging process in closed mold (CCDF) have also been proposed to apply severe plastic strains. Currently, the ECAR process is only performed in laboratories because parts need to be manually removed from the mold. But for industrial applications, it is necessary to develop continuous techniques that can be used in this process. Therefore, in this research, the influencing parameters in the ECAR process will be identified and the rolling machine will be designed and built according to the mentioned method. Then the process parameters should be checked on the mechanical properties and microstructure of the steel-aluminum double-layer exploded welding parts.

1-4- Definition of keywords

1) Extreme plastic deformation is one of the methods of obtaining very fine crystal microstructures in various metals and alloys, through which different crystallographic structures can be obtained, which causes the formation of grains. At the nanometer scale, it begins in the coarse structure, as a result of which the improvement of mechanical properties is observed in metals.

2) Nanomaterials, materials that have at least one of their dimensions on a scale of 1 to 100 nanometers, are called nanomaterials or nanomaterials. This topic is placed in the form of topics related to nanotechnology. Nanotechnology is the ability to produce and build new materials, tools and systems by taking control at the nanometer scale, that is, atomic and molecular levels, and using the properties that appear on these levels.

3) Mechanical properties, including hardness, strength, modulus of elasticity and fracture toughness, which determine the behavior of materials against incoming forces. If the mechanical properties of a piece with a specific shape and composition do not match the desired values, the desired value can be achieved by changing the composition of the material and using different methods such as strengthening mechanisms (fine graining).

4) Rolling in ECAR equal-angle channels is a method of severe plastic deformation on metal sheets and strips that can cause the creation of ultra-fine grain structure in the material. Through this process, it is possible to apply large strains to the material without changing the cross-sectional area of ??the piece and achieve the appropriate characteristics.

5) Explosive welding sheets, welding of non-homogeneous metals through conventional methods has always been a problem for various industries. Because, on the one hand, the difference in the physical properties of the materials causes defects in the weld metal, and on the other hand, the formation of harmful intermetallic compounds greatly reduces the mechanical properties of the connection. Therefore, in recent years, there has been a greater tendency towards solid state welding methods. Explosive welding is one of the types of solid state welding methods, the basis of which is the mechanical connection on the atomic scale between the interface of two metals. In this process, by means of the force resulting from the explosion of an explosive substance, two connecting surfaces collide obliquely at high speed and create a very suitable connection from a physical point of view. Research Workshop of the Jassib University was done. After the design and manufacture of sheet metal ECAR prepared to pass the standard format STDA of the device, the results were reported as follows ECAR able to pass various ways by reducing the metal size increased elongation and changes in yield strength, ultimate strength and was tough.