| Maximizing Refractory Service Life |
Thermal cycling, thermal shock, mechanical impact or vibration can all cause cracking, which in turn can lead to premature failure and substantial cost penalties. Achieving maximum refractory service life at a minimum cost is therefore a key element in the efficient operation of these processes, and in enabling companies to maximize their competitive edge.
The addition of Sunshine Melt Extract steel fibers to castable, gunning and moldable refractories inhibits crack formation (Figure 1) and transforms the conventional refractory from a brittle material to a tough and tenacious composite (Figure 2) exhibiting dramatic improvements in service life.
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| Zhuzhou Nanfang Steel Fiber Co., Ltd is the refractory industry's No. 1 supplier of stainless steel fiber and is dedicated to product development and customer service. |
| The Best Choice for Casting and Gunning |
Melt Extract stainless fibers are fully annealed and therefore are more pliable and ductile. This is of particular benefit during the mixing cycle and when the refractory composite is installed.
These pliable fibers are not only more user friendly than the stiff "needle-like" cut fibers, but also have better flow characteristics. Dispersion is further aided by the optimum Aspect Ratio design guaranteeing rapid fiber separation during the mixing phase.
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The ability to install fiber reinforced refractory mixes by gunning is an important consideration in today's modern refractory industry.
Melt extracted fibers are specified as a mandatory requirement by most international petrochemical companies where fiber containing mixes are routinely gunned inside large processing vessels and ductwork.
During gunning, annealed RS fibers readily pass through the equipment with minimal additional wear.
Cold drawn wire fibers can cause real problems. The "stiff, inflexible" fibers often bridge the ports and orifices in the gunning machine, with resulting blockages leading to expensive delays and wasted materials.
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| 50% Less Rebound |
| Melt Extract steel fiber fiber also has a major influence on the cost of the sprayed linings. On impact with a sprayed surface, the majority of ductile fibers contained within a mix stay in place, whereas a high proportion of the stiff drawn wire fibers rebound, resulting in a very expensive waste material. Rebound loss of RS fibers is typically 50% less than that of drawn wire fibers. |
| Perfect Refractory-Fiber Bond |
| The rough cast surface texture and irregular profile of Melt Extract steel fiber guarantees "mechanical interlock" with the refractory matrix (Figure 3). The unique "kidney shaped cross-section" (Figure 4) provides a higher specific surface area for bonding than round or flat fibers, and is free of surface lubricants which are often present on chopped wire and slit sheet fiber and which prevents bonding. |
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| Superior Resistance to High Temperature Corrosion |
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Melt Extract stainless steel fibers are spun directly from the melt using the company's advanced Melt Extraction (ME) and Melt Overflow (MO) processes. Rapid cooling of the fiber during manufacture (equivalent to 50,000 per second) "freezes" the metallurgical structure, capturing it in an optimum state to resist high temperature corrosion - a state which is impossible for conventionally cast steel to match.
The processing maximizes the effective distribution of the primary nickel and/or chromium alloying elements throughout the fiber while simultaneously minimizing grain size. When coupled with Sunshine’s skill of blending non-standard levels of performance-enhancing key trace elements to the melt, a unique range of dedicated refractory fiber alloys have been produced which provide outstanding oxidation resistance and unmatched performance at elevated temperature (Figure 5).
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| Fiber Size |
The normal diameter of stainless steel fiber is 0.3mm~0.7mm with a length of 20~60mm. To avoid agglomeration during sirring, the ratio of the length to the diameter shoud be controlled in the range of 30~80. It should be noted that if a process of jet spray is applied, stainless steel fiber of a shorter length <25mm should be selected, otherwise the spray jet shall be blocked.
For special applications other lengths and diameters are also available.
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Fiber Grade: The grades of steel fiber should be suitably selected based on the temperature and atmosphere.
1. Fiber Packing: Steel fiber should be first spread evenly into the refractory materials, and mixed in a dry state and then in a wet state. To avoid the difficulty of installation due to agglomeration, a packing of an orderly array in paper boxes should be first considered.
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| Fiber Costs Up to 50% Lower than Comparable Products |
Cost savings are the main reason for adding stainless steel fibers. In all areas of high thermal and mechanical shock, fibers will at least double refractory life.
Sunshine’s low cost/high performance melt extract steel fibers provide the quickest payback. Our quality product costs substantially less because we produce our molten steel and spun fiber on-line in one fully integrated manufacturing plant. We are able to keep fiber manufacturing costs to a minimum, which is reflected in the very competitive prices .
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| Fiber Addition Rates |
It is essential to include sufficient fiber in the mix to prevent the microcracks which develop under thermal stress from propagating into visible cracks which lead to premature refractory failure. International experience has proven that the most cost-effective fiber addition for enhanced serviceability, irrespective of fiber type used, is 1% by volume. (This is equivalent to 3-4% by weight for most non-insulating refractory mixes.)
In an endeavor to trim initial costs, a few refractory suppliers have been tempted to use fiber contents as low as 2% by weight. This is contrary to the current trend towards the use of higher fiber dosage levels (up to 6% by weight) to maximize service life (see Figure 2). Manufacturers of expensive drawn stainless wire fibers often promote 2% fiber addition in an effort to present their product as "competitive". This approach is in reality a false economy, since the associated reduced service life of the composite makes the low fiber containing refractories work out significantly more costly over their shorter service life.
Attempts to support the argument for "low fiber addition" by simple laboratory tests of strength and toughness are misleading and do not reflect "real life conditions".
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SUNSHINE melt extract steel fiber of our company impart increased thermal shock resistance, steep thermal gradients resistance and mechanical shock resistance, minimizing damage and delaying failure caused by cracking. By increasing refractory lifetimes steel fiber refractory reinforcement offers the end user a reduction in downtime and substantial savings in materials and labor costs. |
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| The lowest heat resistance of SUNSHINE melt extract steel fiber: |
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| Physical, Mechanical and corrosion resistant properties of stainless steel fiber |
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