A crafts forum. CraftBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » CraftBanter forum » Craft related newsgroups » Glass
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Wear Of Fused Cast AZS Block In The Superstructure And Crown



 
 
Thread Tools Display Modes
  #1  
Old June 9th 15, 10:53 AM posted to rec.crafts.glass
Sunriserefractory
external usenet poster
 
Posts: 1
Default Wear Of Fused Cast AZS Block In The Superstructure And Crown

In the past, wear of superstructure refractories, primarily silica crowns, is probably the most serious concern. Fused cast AZS block has been suggested as an alternative to the traditional silica crown as it has good corrosion against and can slow the wear of superstructure and improve the life of the furnaces.

Superstructure and crown refractories are subjected to corrosive reactions with the vapor species of the batch components and batch carryover. In the melting of soda-lime glasses, the vapor species are primarily soda and sodium sulfates. For borosilicate glasses, Na-tetraborate and B2O3 predominate. Direct attack occurs by condensation of the hot face of the refractory. The chemical changes in this reaction zone result in mechanical stresses and flaking, peeling or spalling of the hot face. Vapor penetration into joints with subsequent condensation and corrosion lowers the mechanical integrity of the superstructure or crown.

Corrosion phenomenon in superstructure have environmental and intrinsic causes. Heavy metals from fossil fuels, volatile component of the glass can reach the refractory surface as vapors, but the most severe attack can be caused by silica, reaching the surface as dust. Silica reacts easily with the corundum crystals of the Fused Cast AZS and, with the contribution of refractory's soda, produce sodium-alumina-silicates, pealing off the external layer of refractory, exposing deeper layers to corrosion and so forth.

At temperatures above 1475 ℃, the bond strength between the embedded ZrO2 crystals and the alumina is reduced, attributed to the variation in the thermal expansion characteristics of A12O3 and ZrO2.

Fused Cast AZS Block that are not exposed to peculiar environmental attack. In some case, due to recurrent thermal cycling and subsequent multiple exudation, the refractory is losing very significant amounts of glassy phase, extruded with a gas-driven mechanism, replacing it with increasing amounts of closed porosity. When this happens, in relatively deep zone under the hot face there is formation of mullite by reaction of silica of the glassy phase and corundum crystals; while minor amounts of alkaline glassy phase are extruded, the increasingly acidic refractory structure undergo progressive mullitization. Volumetric changes and depletion of the liquid phase necessary to absorb the thermal dilatation of crystalline components are concurrent causes of possible cracking and deep spalling of surface, as a consequence of intrinsic corrosion subsequent to exudation.

While the wear of fused cast AZS block in the superstructure has been a potent and long-term source of glass defects, it is proved a longer service life as superstructure refractories in glass melting furnaces and other similar applications, it still encounters wear in the superstructure.
Ads
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
knithink ...when cast on hand stops cast on stitches ,,, Mirjam Bruck-Cohen Yarn 2 November 13th 07 01:12 PM
HMS Daring Superstructure Eddie Quilting 11 July 12th 07 04:48 PM
Blown, Cast, and Fused Contemporary Glass Sculpture from Holsten Galleries H.Atterbury Beads 2 October 19th 04 03:18 AM
Blown, Cast, and Fused Contemporary Glass Sculpture from Holsten Galleries H.Atterbury Glass 0 October 18th 04 11:34 PM


All times are GMT +1. The time now is 01:01 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 CraftBanter.
The comments are property of their posters.