Bismuth Manganese cored wire

Product Description:

Bismuth Manganese cored wire is the source of bismuth addition in steel, which is used to enhance the machinability of steel and manufacturing of
free cutting steel.

No ImageBismuth manganese cored wire is prepared by high grade of Bismuth and Manganese powder, which is filled in U shaped steel sheath (made of high quality of steel strip) and this U shapes steel sheath is closed tightly (Fig-­1), so called overlapping craft, with help of equipment. The encapsulated bismuth manganese in steel sheath (called cored wire) is injected into the steel melt with help of wire injection system with the purpose of high recovery of bismuth in steel than the virgin bismuth shots addition into the ladle.

The powder specification of bismuth manganese, which is used in cored wire, strip specification, & wire characteristics, is given below:

Grade Powder Chemical Composition (%)
Bi(Min) Mn(Max) flux
BiMn 88 -­ 90% 4 -­ 6% ~ 5%

 

Powder specification
Grade density (g/cm3) Melting
Point
(°C)
Boiling
Point
(°C)
Size (mm)
BiMn

Bi -­ 9.78

Mn -­ 7.21

271.8

1246

1564

2061

-­ 1.4+0.106

-­ 1.4+0.106

Strip Specification
Grade Diameter
(0, mm)
Thickness (mm)
EDD IS-­513 9± 0.5 0.4 ± 0.03
Wire Characteristics
Grade Diameter ( 0, mm) Shape Powder Fill (gm/mt)
Bi Mn 9± 0.5 Round 380±20
Coil Specification (Flipping Coil – Horizontal & Vertical)
Details

13 mm 0

F1-02

Coil Identification
Powder Weight
(MT)
0.500

All coils are color coded and fixed with a detailed sticker clearly displaying details such as coil no., powder content, strip weight, gross weight density & length. A fluorescent sticker displays the name of the product in bold letters on the outer diameter of the coil.

Handling

No metal sling, chain or rod is to be used across the ID of the coil for handling as it may damage the coil. Use only polyester, synthetic slings, fork lift/tractor to handle the coil. The pallet is an integral part of the coil and it is to be removed till the coil is consumed.

Shelf Life

Follow the shelf life period specified by MINEX








Strip Weight
(MT)
0.180
Net Weight
(MT)
0.680
Length (Mtrs) 1315
Internal
Diameter (mm)
650
External
Diameter (mm)
780
Height (mm) 630
Packing Storage & Safety

Packed in flipping cage and mounted on wooden / mild steel pallet and Strapped with pallet horizontally or vertically. All coils are wrapped in stretch film & palletized.

To be stored in dry & covered area away from heat and moisture. Material Safety data sheet can be Supplied on demand.

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Addition and Addition Technique:

In steel making, bismuth can be added to molten steel in the ladle or as the molten steel is introduced into an ingot mold or tundish. It is normally desirable to add alloying ingredients to the molten steel into the ladle because, in theory at least, when so added, the alloying ingredient should be more uniformly distributed throughout the entire volume of steel.

No ImageThe addition of alloying elements and close control over the degree of addition is an important step in steel making process. There are various ways to add bismuth or its alloys in steel as bismuth shots, ingot, cored wire etc. The addition of virgin bismuth shot to the ladle at steel temperature cause very low recovery (the recovery up to 30 – 50%.), because of Bismuth has low melting point (271°C) and boiling point (1560°C), that cause evaporation and also bismuth addition agents are denser than liquid steel and gravitational segregation can be a problem.

But in case of bismuth cored wire, bismuth with manganese and flux is encapsulated in steel sheath, when injected into steel it can go in depth of steel melt as shown in above figure 3, as steel sheath is melted Bi is dispersed into the melt. The argon purging into the ladle helps to distribute the bismuth
throughout the melt and helps lesser gravitational segregation. The cored wire goes deep into the melt causing high recovery;; this recovery can exceed 95% because of:

  • Due to ferrostatic pressure the evaporated Bi slowly rise to surface and react efficiently in steel melt.
  • Presence of Mn and flux reduces evaporation of Bi significantly and hence lower evaporation loss and high recovery.

No ImageAfter the addition, Bi may undergo the problem called "bismuth fade"i.e. decreasing bismuth content in the molten steel during the time, the molten steel is being withdrawn from the ladle. This happens due to the vaporization of bismuth at the surface of the molten steel in the ladle followed by an oxidation of the bismuth vapor. Lower addition temperature and reducing pouring time can reduce the problem of bismuth fade. Keeping a layer of slag at the surface of melt is also beneficial as it reduces the rate of evaporation.

Amount of Bismuth addition::

Addition can be made depending upon the grade of steel and impurities present in steel. Generally in the free cutting steel, the bismuth content is in the range of 0.05-0.40 wt. %. Bismuth has a relatively low melting point (271° C.), and the surface free energy value for bismuth at a temperature near its melting point is relatively low (375 ergs/cm 2). As a result, absence of any interference with these properties, bismuth has a strong tendency to wet steel grain boundaries or interphase boundaries at a distance relatively far away from the cutting edge of the machining tool, thereby embrittling those regions for easy fracture.

The surface free energy value of bismuth at its melting point is increased, and hence the ability of bismuth to wet grain boundaries or interphase boundaries is decreased, by certain elements, most of which are normally present as impurities in steel. These elements comprise copper, nickel, tin and zinc. Copper, nickel and tin are normally present as impurities in steel in amounts up to about 0.1 wt. % each.

Thus amount of bismuth is added in such a way that the total amount of ingredients which lower the wetting ability of the bismuth is less than the bismuth content of the steel, and the total amount of these ingredients :- % (Cu + Ni + Sn + Zn) < 0.6 x %(Bi) And also the ratio :- %Bi / (%Ni +%Cu) ?. 2.0.

The ratio of bismuth to the sum of nickel and copper is important and should not be lower than 2.0. This utilizes the low melting point of bismuth for increased machinability, as ratios lower than 2.0 will diminish the effect of bismuth.

Application and Advantages:

Small amounts of bismuth are used to enhance the machinability of metals, especially steel, a use fostered by concern about the toxicity of lead, a traditional free-machining additive for this purpose. Bismuth has been used both as an additive to resulfurized, rephos-phorized, and leaded AISI 1214 steel and as a substitute for lead in AISI 1214 and 1215 steels. As a substitute, it is believed to improve machinability in a manner similar to lead. As an additive, it alloys with lead, one half the lead content, typically 0.1%Bi, and 0.2%Pb. providing more effective internal lubrication than lead alone, further improving machinability.

Bismuth is added individual in amounts to 0.05 - 0.4 wt %, typically 0.2 wt % depending on requirement and presence of impurities. Its advantages over lead also have been attributed to its lower density, which permits more uniform dispersion in the steel matrix. It has no strong effect on mechanical properties but substantial improvements in machinability.

Bismuth like lead thought to act as an internal lubricant, reducing the friction between tool & chip. Bismuth improves machinability because it has the lowest melting point among free-machining additives and the strongest ability to weaken interfacial boundaries. Bismuth exists in the form of particles/ inclusion attached not only to manganese sulfide inclusions, but also to ferrite-pearlite interfaces and grain boundaries, which intensifying its effec-tiveness of machining and provides 20-30% improvement in machinability than lead. Tellurium and selenium can be added with Bismuth, because they also enhance the wetting ability of bismuth in steel.

No ImageBismuth has no effect on transformation or microstructure produced by heat treatment in steels. Bismuth is not, however added to Nickel-Bearing austenitic stainless steels since it seriously impairs hot workability in these materials as shown in figure- 4;