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3.Furnace Workshop
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3.Pouring Workshop(Furnace Workshop)

Tunnel furnaces are employed to roast the sand shells.
After a period of drying ,sand shells are then put into the tunnel furnace and roasted at a high temperature.Sand shells are put on carts which then are pushed into the furnace for roasting.The total weight of the steel water for the shells on one cart should be equal to that of one furnace of steel water.Only shells with the same steel designation are put on the same cart. The pouring basins are forbidden to face the opening through which coals are added into the furnace .Neither are the basins allowed to face upward.

Raw material adding:

First, put the clustered scraps into the smelting furnace (medium frequency electric furnace),add alloying elements if it is alloy steel,and add iron scraps until the steel liquid take up the 75% of the furnace.When the steel liquid turns white .AI wire is used for deoxidation and the steel liquid is ready for the first chemical analysis where spectrograph are employed. If the result of the first chemical analysis shows that composition conforms with what is required,than the steel liquid is ready for pouring.Or Otherwise,the composition should be adjusted by adding appropriate materials and be sent for more chemical analysis until the result shows that the composition accords with the specific steel designation.

After the adjustment of the chemical composition. The temperature is then raised up to 1630--1650℃(temperature controller is used).When the steel liquid id white with heavy smoke,press the red button to put the electric speed reducer into motion ,which can tilt the furnace, and thus the steel liquid is poured into the casting ladle.Then two men carry the ladle and pour the steel liquid into sand shells which have already been buried in the sand,at a high or low speed (as required by specific techniques). The shells are cooled in sand for20-30 minutes (determined by the physical dimension and production conditions. Generally 30 minutes for large ones and 20 minuter for smaller ones).If they are pulled out too early , deformation of hot cracking may occur;if pulled out too late, decarburized layer may occur in some castings with high carbon content.



  • 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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