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Do you really know what shot blasting is? What are the advantages and disadvantages?
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Do you really know what shot blasting is? What are the advantages and disadvantages?

Views: 48     Author: Site Editor     Publish Time: 2018-08-07      Origin: www.fuchun-casting.com

Many have heard the term shot blasting, but what exactly is shot blasting and what are the benefits of shot blasting?

 

What is Shot Blasting?

Manufactured metal parts aren't ready for use right out of the mould. They often need a coat of paint, powder coating, or welding work. But before this can happen, the surface of the metal part must be clean.

Shot blasting prepares metal parts for further processing like painting or powder coating. This step is necessary to ensure the coat adheres properly to the part. Shot blasting can clean off contaminants like dirt or oil, remove metal oxides like rust or mill scale, or deburr the surface to make it smooth.

 

How Shot Blasting Works?

Shot blasting involves shooting a high-pressure stream of abrasive material (also known as shots or blasting media) against the surface of a metal part. Depending on the application, the shots may be propelled by a pressured fluid (like compressed air) or a centrifugal wheel (known as wheel blasting).

The shape, size and density of the shots will determine the final results. Types of metal abrasives used in shot blasting include steel grit, copper shots, and aluminum pellets. Other methods of shot blasting use silica sand, glass beads, synthetic materials like sodium bicarbonate (baking soda), and even agricultural materials like crushed kernels.


Shot Blasting process

 

But sometimes we find that the casting surface will be blackened after shot blasting. Black spots on the surface can be removed, but it is difficult to treat those that have been immersed in the casting matrix.

The reasons for this are as follows:

1. Defects before shot peening brought by die casting process;

(1) excessive use of black oil in die casting;

(2) Punch oil splashing during die opening;

(3) Paint splashing during die casting;

2. The product is placed in wet temperature or time, and the surface is corroded, mildewed or dusty.

3. The dust removal device of shot peening machine is invalid, and the steel shot contains more dust.

4. The operator did not wear gloves according to the requirements, and directly touched the surface of the casting after shot peening with his hands, resulting in fingerprints.

5. After shot peening, it will be put for a long time. The surface will be covered with dust or splashed with water and oil. The environment will be humid and oxidized.

 

When the above situation occurs, corresponding measures should be taken:

1. Defects do not cover the whole casting surface. Control and management should be strengthened by die casting process.

2. After shot peening, the surface trace is shallow and can not be removed because it has been immersed in the casting matrix. The management of product placement should not be too long. If it needs to be placed for a long time, it must be covered and protected in suitable environment.

3. The surface color of the whole casting is black and dark. Restore dust removal or replace new steel balls;

4. Operators must be required to follow the operation instructions. Gloves must be worn.

5. Shot peening should be finished, packed and stored as soon as possible. If it needs to be stored for a period of time, strict protection must be carried out.



 


Products

FAQS

  • What is 'multiple certification'?

    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.

  • What surface finishes are available on stainless steels?

    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.

  • Can I use stainless steel at high temperatures?

    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:

    1. Maximum temperature of operation
    2. Time at temperature, cyclic nature of process
    3. Type of atmosphere, oxidising , reducing, sulphidising, carburising.
    4. Strength requirement

    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.

  • Can I use stainless steel at low temperatures?

    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. 

  • Is stainless steel non-magnetic?

    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.

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