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Views: 6 Author: Site Editor Publish Time: 2018-03-31 Origin: Site
H2. Precision casting technology can be summarized in developed countries to protect the environment, improve casting quality and reliability, reduce production cost and shorten delivery time.
H3. Ductile iron casting technology as an important part of casting technology, research on ductile cast iron casting should be on the "highway" as soon as possible. Looking forward to its development trend, our ductile iron casting technology, especially the thick wall parts, should be developed rapidly in the future.
H4. 1.Vigorously develop new spherification and gestation technology. The driving force of high strength and high ductile ductile iron production is the continuous improvement and improvement of spheroidization and gestalt technology. The development of gestation technology often hopes to develop new inoculants. However, in recent years, the improvement of breeding methods, especially in late pregnancy, has been taken seriously. Therefore, at the same time, the research on the pregnant technology will be changed to develop new incubation methods.
H5. 2.The research on new materials and new process of ductile iron should be the main objective of automobile industry, aerospace and nuclear energy industry, which is characterized by strength, lightness, precision and efficiency.
H6. 3.Ductile cast iron casting process is a complex irreversible process. In actual production, there are many uncontrollable factors or immature processes that lead to the castings being scrapped or unable to reach the desired technological targets, To carry out basic theoretical research on major technical equipment and precision casting technology, Develop numerical simulation, physical simulation and expert system, to make ductile cast iron foundry technology from "experience" to "quantitative".
H7. 4.Development of green intensive casting, to increase the precision casting process to environmental pollution control, to strengthen the regeneration and reuse of precision casting materials.
H8. 5.Realize online and intelligent. Ability to detect and control precision casting process or equipment online, ability to timely and accurately reflect the status of the site, to control the production equipment in real time so that the precision casting process or equipment is in the best condition.
This is where a batch of steel meets more than one specification or grade. It is a way of allowing melting shops to produce stainless steel more efficiently by restricting the number of different types of steel. The chemical composition and mechanical properties of the steel can meet more than one grade within the same standard or across a number of standards. This also allows stockholders to minimise stock levels.
For example, it is common for 1.4401 and 1.4404 (316 and 316L) to be dual certified - that is the carbon content is less than 0.030%. Steel certified to both European and US standards is also common.
There are many different types of surface finish on stainless steel. Some of these originate from the mill but many are applied later during processing, for example polished, brushed, blasted, etched and coloured finishes.
The importance of surface finish in determining the corrosion resistance of the stainless steel surface cannot be overemphasised. A rough surface finish can effectively lower the corrosion resistance to that of a lower grade of stainless steel.
Various types of stainless steel are used across the whole temperature range from ambient to 1100 deg C. The choice of grade depends on several factors:
In the European standards, a distinction is made between stainless steels and heat-resisting steels. However, this distinction is often blurred and it is useful to consider them as one range of steels.
Increasing amounts of Chromium and silicon impart greater oxidation resistance. Increasing amounts of Nickel impart greater carburisation resistance.
Austenitic stainless steels are extensively used for service down to as low as liquid helium temperature (-269 deg C). This is largely due to the lack of a clearly defined transition from ductile to brittle fracture in impact toughness testing.
Toughness is measured by impacting a small sample with a swinging hammer. The distance which the hammer swings after impact is a measure of the toughness. The shorter the distance, the tougher the steel as the energy of the hammer is absorbed by the sample. Toughness is measured in Joules (J). Minimum values of toughness are specified for different applications. A value of 40 J is regarded as reasonable for most service conditions.
Steels with ferritic or martensitic structures show a sudden change from ductile (safe) to brittle (unsafe) fracture over a small temperature difference. Even the best of these steels show this behaviour at temperatures higher than -100 deg C and in many cases only just below zero.
In contrast austenitic steels only show a gradual fall in the impact toughness value and are still well above 100 J at -196 deg C.
Another factor in affecting the choice of steel at low temperature is the ability to resist transformation from austenite to martensite.
It is commonly stated that “stainless steel is non-magnetic”. This is not strictly true and the real situation is rather more complicated. The degree of magnetic response or magnetic permeability is derived from the microstructure of the steel. A totally non-magnetic material has a relative magnetic permeability of 1. Austenitic structures are totally non-magnetic and so a 100% austenitic stainless steel would have a permeability of 1. In practice this is not achieved. There is always a small amount of ferrite and/or martensite in the steel and so permeability values are always above 1. Typical values for standard austenitic stainless steels can be in the order of 1.05 – 1.1.
It is possible for the magnetic permeability of austenitic steels to be changed during processing. For example, cold work and welding are liable to increase the amount of martensite and ferrite respectively in the steel. A familiar example is in a stainless steel sink where the flat drainer has little magnetic response whereas the pressed bowl has a higher response due to the formation of martensite particularly in the corners.
In practical terms, austenitic stainless steels are used for “non-magnetic” applications, for example magnetic resonance imaging (MRI). In these cases, it is often necessary to agree a maximum magnetic permeability between customer and supplier. It can be as low as 1.004.
Martensitic, ferritic, duplex and precipitation hardening steels are magnetic.