Views: 50 Author: Site Editor Publish Time: 2018-11-05 Origin: www.fuchun-casting.com
The quality of products is the basis for the survival and development of enterprises. Improving the quality of machined workpieces is an urgent task for every large-scale machined factory. How do we improve the quality of workpieces?
1. Improving the cutting level
In mechanical processing, when the workpiece is machined, the surface of the workpiece will form almost the same mark as the shape of the cutter and leave a large number of scales. It is easy to increase the roughness and reduce the quality of the workpiece surface. Generally speaking, in this case, in order to ensure that the roughness of the workpiece surface is controlled within an appropriate range, the radius of the cutting tool tip arc should be increased appropriately, and the feed of the cutting tool should be reduced appropriately, so that the height of the residual area of the cutting tool on the workpiece can be reduced as much as possible. This can effectively reduce the workpiece surface debris and scales, improve the quality of the workpiece surface.
2. Improving Cutting Speed
When a workpiece is machined, if the cutting speed is faster, the deformation degree of the workpiece can be reduced, and the faster the cutting speed, the smaller the deformation degree, which can effectively reduce the roughness of the workpiece surface. If the cutting speed is not fast enough, the workpiece will produce chip tumors in the cutting process, which will affect the surface quality of the workpiece.
3. Improving the Accuracy of Machining Equipment
Workpiece processing is mainly accomplished by machine tools. The errors of machine tools will directly affect the accuracy of the workpiece. This requires ensuring the accuracy of the machine tool itself, which can effectively reduce errors. The error of tool and fixture will also affect the accuracy of the workpiece. Corresponding measures can be taken to reduce tool wear, which can also improve the accuracy of the workpiece.
We have a sound quality management system, the pursuit of excellence business philosophy, customer satisfaction-oriented, continuous improvement as the driving force, sincerely look forward to working with all customers to create the future for enterprises to provide high-quality products!
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.