The safe and stable operation of the train can not be separated from 24 hours of maintenance guarantee every day. When the replacement parts are needed and no replacement parts can be found, the railway department should contact the manufacturer to provide them quickly.
2019.06.14
Read MoreHave you seen this cat paw cup circulating on the internet recently? Starbucks China launched this unique double-walled glass cup on Thursday (28 Feb).
2019.02.28
Read MoreIn the last few years, metal 3D printing has become increasingly popular. One reason metal 3D printing has become such a hot topic is that parts can be serially 3D printed for mass production. In fact, some parts created with metal 3D printing are already just as good, if not better, than those manufactured by traditional methods.
2018.12.31
Read MoreIn January, the U.S. government decided to impose high protective tariffs on imports of solar panels and washing machines, and in February, the U.S. Department of Commerce finally decided to impose high anti-dumping and countervailing duties on imports of Chinese aluminum foil.In early March Trump announced a 25% tariff on imported steel and a 10% tariff on aluminium, throwing a blockbuster bomb on international trade and global financial markets.
2018.11.01
Read MoreFifty years ago, a rare and unusual sword was found in a tomb in China. Despite being well over 2,000 years old, the sword, known as the Goujian, did not have a single trace of rust.The blade drew blood when an archeologist tested his finger on its edge, seemingly unaffected by the passage of time. Besides this strange quality, the craftsmanship was highly detailed for a sword made such a long time ago.
2018.10.31
Read MoreAround the 21st century BC, China entered the Bronze Age,which saw the growth and maturity of a civilization that would be sustained in its essential aspects for another 2,000 years.Yin-Shang bronzes mark a peak in the late Bronze Age all over the world, with a variety of fine bronze wares, e.g.,
2018.10.25
Read MoreOn March 1, 2018 Trump announced his intention to impose a 25% tariff on steel and a 10% tariff on aluminum imports,what will be the impact on countries?
2018.09.07
Read MoreA CNC, or computer numerical control machine is a high precision tool that’s computer-controlled and makes repeated, accurate movements. It does so by taking computer-generated code and converting it with software to electrical signals. The signals are what control the CNC motors and directs them to move in small increments that are highly precise and repetitive.
2018.08.10
Read MoreThere are two machining centre forms, the horizontal and vertical. This refers to the main spindles orientation. Both the horizontal and vertical machining centres come in small, bench-mounted devices to a room-sized machine.
2018.08.03
Read MoreAgriculture as a primary industry should be very important for a developing country like China.As far as agricultural machinery is concerned, it is the product of industry developing to a certain stage and feeding back agriculture, so it has both industrial characteristics and agricultural characteristics.
2018.07.20
Read MoreThis 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.