Refractory anchoring systems

 How important are anchoring systems on your refractory linings? 
- How does your company engineers this systems? 
- Can you trust on your suppliers for technical advice? Wich alloy suits best your lining, your equipment, etc.
- Is anchoring systems a matter of price, do you look at it as a commodity?


the anchor system is critical to the success of the Furnace Lining. 

Indeed, you get what you pay for but anchoring will be a fraction of your build spend so to 'pinch pennies' in this area is a false economy, resulting in premature failure perhaps. 

Key points which determine the engineering of you anchor system: 

* Lining thickness & construction - What material(s) are you retaining? 
* Operating Conditions - Temperature, thermal cycling, atmosphere, mechanical stress 
* Plane of Refractory - Roof, wall, bull-nose? 
* Openings within the refractory body - flue opening 

This determines the type of anchor (material) & quality (grade) you should be expecting to use. 

I would suggest that the anchoring design is based on experience and good practice. 


Additional to what has been said already. Your total lining needs to be designed for its purpose. Thermal expansion can destroy a lining regardless of the anchors system while it may appear to be anchor failure. Consideration of refractory load on any give area is also a consideration for anchoring design. If the vertical load is not transferred back to the shell with shelf supports, you may see failures that look like and anchor failure, when reality is improper anchor application. Shelf supports are also used to isolate areas which may be exposed to thermal expansion from two walls. Bull noses and corner are examples that one would isolate. 

It is difficult to find installation companies that will offer anchor design because they do not want to be exposed to any liability. Some do. 

We have improved the performance of one of our client calciners to operate continuously for 3-4 years. Improved from have outages every 6 months. A huge factor in the improved performance was changing the anchor design.


 a change from standard 310s to 253MA in many industries. This could be for several reasons. Having worked at Rolled Alloys and knowing the differences between each alloy I think one needs to have a good understanding of metals and their behaviour and to know when and where to apply which alloy. One furnace is not the same as another. I have seen anchor failures in 253MA and 310s in similar applications but all for very different reasons that the applicator thought they would survive. I don't always understand why suddenly an alloy is 'in' but it could well be because of lack of understanding of the alloy or just 'everybody is going that way' or some sort of hype, so "lets follow". My experience is that the life time of an alloy actually depends on the alloy chemistry AND the condition in which it is furnished. Both play about a 50-50 part as opposed to just the chemistry. Alloy content determines strength as well as the corrosion resistance of the elements it is endowed with but the surface tension determines the rate at which corrosion takes place. A rough surface will be more susceptible to attack than a smooth surface and a black solution annealed surface wll be attacked/corroded faster than a bright annealed surface. Bright Solution Annealing od a cold drawn or rolled surface is usually the way to go. What people also forget is that each alloy needs to be solution annealed at different temperatures for different lengths of time. If the recepie for all the above is not correct one will not have the full benefit out of any alloy and remain in the dark as to why it worked one time and not the next. One usually forgets he paid the cheapest supplier to get him something he thought was the same as anothers. 

There is also lot of misunderstanding about Sigma forming in stainless steel alloys and very little written about it. I have seen write ups and theories that are totally incorrect and others usually prior to 1970 that would be closer to the truth. One such belief is that 253MA is immune to Sigma formation. This is not true. I have seen annealing bells crack like glass in cold swedish winters after only months of service. Immunity to Sigma is only offered by sufficient Nickel or Cobalt content. There are a few other elements but due to the commercial nature of these alloys it is usually shyed away. I think the industry may reconsider 253MA as an anchoring alloy unless it is used for the purpose for which it was designed. This was to offer better sulphadation and oxidation resistance against 310 and 310s. Not to offer better sigma formation resistance as many believe with such certainty. It would be a great alloy for incinerators and SO2 containing gasses. One must consiously know one has selected the right alloy. If one has not, that will be the time it bites back at him.


When deciding which alloy to go for, it is absolutely critical to know the how each alloy will behave under the various conditions it is exposed to. It not just a matter of price. We have noticed that certain markets prefer to use Grade 304 because it is cheaper yet most don't realise that is grade is not suitable for excessive temperature exposure or aggressive corroding atmosphere therefore increasing their maintenance and labor cost in the long run. 


 the Sigma phase formation and susceptibility as well as the lack of sufficient publications to support the arguments. 253MA is not immune but it is less susceptible than 310. Incoloy DS and Inconel 601 are better alternative but at premium price due to the higher Ni content. 
Special alloys such as Haynes 160 and 120 can offer even better solutions however they do come at relatively higher prices. 

As far as I know, using traditional V-anchors really can do a good job if you don't need a lifespan of more than a year in very harsh conditions. If one wants a long life time and the temperature is too high for anchors to survive (in my opinion above furnace temp of 1200 degrees C or more), then one should consider ceramic anchor systems. If the chemicals are the problem, then one can look at exotic anchor materials. Another solution is changing the geometry and make a self load bearing brick solution.
Another aspect that goes wrong many times, in my opinion, is the amount of used anchors. Rule of thumb for me is the anchor distance should be the same as the lining thickness with anchor length being 2 cm shorter than the lining thickness.
Sigma phase cannot be tackled other than assuring the anchor is either not susceptible to that or not used in the wrong temperature range or replaced before the anchor went too many time through the sigma phase related temperature.

the anchoring system you choose will determine the life of the monolithic lining. You must also take care about anchoring if you are gunniting, or shotcreting, as long as ceramic anchors do not retain the gunned material as well as V-shaped metallic anchors. Generally, the V-shaped corrugated free-moving system is a very good option, provided your welders will not close the movable parts with a strong weld seam. 
You should also take care about the environment in which you are installing the monolithic linings. At temperatures below 600-700 °C, I don't see a mechanical problem in installing 310S or 310, but at higher temperatures you should really consider a better alloy, such as Inconel, or 253MA. From the discussion, I believe your major concern are cement kilns. In this case, you should check if there is sulfate or chlorine gas attack in the anchor. Against chlorine very little can be done, thus I recommend a mix of ceramic and metallic anchors (guarantee the clips are of 310S or superior quality and that the anchors do not have their movement restricted. Good wedging is essential!). In this case, you may also consider the change from the V-Shaped anchors to the flat bar concept. I agree 100% that this concept is old-fashioned and lead to higher stresses in the lining, but if an expansion joint is carefully prepared, you have a much larger corrosion area. This concept should be tried if corrosion of the V-shaped 10 or 12 mm anchors is excessive. 
For sulfate, the information from Wouter Garot is perfect. You should avoid nickel in the alloy, thus 253MA is far better than 310 or supperalloys. 
Anyway, wherever corrosion is an issue, the mix of ceramic and metallic anchors is geneally advantageous. 

Functions and Importance of Tundish in Continuous Casting - I

The role of tundish in the continuous casting process evolved from that of a buffer between the ladle and mould to being a grade separator and also a device for removing unwanted inclusions through metallurgical processes / chemical reactions. The tundish is intended to deliver the molten metal to the moulds evenly and at a designed throughput rate and temperature without causing contamination by inclusions. It distributes molten steel in continuous casting moulds and is typically operated at a constant bath depth to ensure a constant feed rate into the mould required to achieve a constant throughput. In the sequence of continuous casting, tundish directly control the molten steel in the last stage of liquid steel processing and the refractories used here are therefore, required to have high stability and special properties. Tundish is one of the most important areas of Refractory Application and so, is also one of the biggest ‘cost control center’ in the continuous casting process.

Tundish Refractory Lining


After Bricked Lining and then Gunnable Lining, Tundish Boards (or Board Lining) came into existence as working lining. Silica boards are used for MS grade and MgO boards for SS grade and for high Ca ppm steel. The reason being silica is attacked by lime, alumina and iron oxide present in the steel.


However, for longer duration casting Sprayable Lining such as MgO spray mass (Magnesite spray mass) are widely used with MgO content varying from 70 - 90% and minimum silica content. For example, for 10-12 hrs casting, 70-75% MgO with silica content below 15% are working well. But to achieve 20-25 hrs life, 90% MgO with silica content less than 10% with 35-40 mm thickness at wall and 50-60 mm thickness at the bottom are required. Separate preheating arrangement is required to form the chemical bonding in spray mass after application at around 1000°C.


Of late, tundish spray mass has gradually been replaced by Dry Vibro mass to further elongate the casting sequence. MgO content varies from 70-90% with low silica content to achieve a sequence length of 12-15 hrs to 35-40 hrs. One advantage of Dry Vibro mass is that it ensures low hydrogen pick up in steel as it does not require water for application. Approximately 0.7-0.9 ppm hydrogen pick up is reported as compared to 1.8-2.4 ppm in spray mass. Special drying arrangement is required for drying this mass at around 300°C for 24 hrs to develop polymerisation of resin which gives strength to it.

Ladle Slide Gate

 refractory slide gate plates used, in pair, as a valve at the bottom of the ladle in order to control molten metal flow during casting. Highly sliding surfaces of these plates are necessary for easily opening and closing operation as they slides on each other. 
My question is whether these refractory plates required tar impregnation treatment, because i found this treatment in most of the articles regarding refractory slide gate plates, or it also not necessary require tar impregnation likewise magnesia carbon bricks and can be use directly after curing.


 There are mainly four types of commonly used slide gate plates.These are:

1) Cured Alumina carbon plates
2) Fired alumina carbon plates
3) Cured magnesia carbon plates
4) Fired magnesia carbon plates

Fired plates have better erosion resistance as well as better mechanical properties at high temperature.

Cured plates give 1 heat life and after polishing/coating the plate by repair may give one more extra heat life.

Fired plates can give around 4-6 heats life.

There are also zirconia based plates which are very expensive and used by reputed steel plants who targets to achieve 8-10 heats per pair of plates.

Magnesia based plates are preferable where slag corrosion rate is very high.

Tar impregnation is effective on fired products.After firing,the plates can have a porosity of about 13-14%.After tar impregnation,the porosity is reduced to around 3 %.

Tar impregnation is not much effective on cured products,as cured products already show a porositiy of about 5 %.

Purpose of tar impregnation are to lower the porosity and increase the carbon content.This results in better thermal conductivity and oxidation resistance.In case of Alumina carbon plates,tar impregnation also protects the aluminium carbide from hydration.

So,I will say,although environmentally hazardous,tar impregnation is necessary for fired slide gate plates.

whether TAR IMPREGNATION is a necessary step in production of magnesia carbon bricks or it is an additional process in order to improves the quality of bricks and it may be avoided????

Magnesia carbon bricks which we normally use have black shiny appearance with slippery surface, leaving carbon on touch. 
Is it possible to get such appearance after curing only i.e. after holding at 250C or above, or after curing + pyrolysis , or we must need to go for impregnation step in order to have such an appearance of brick, ready for lining.


If we go through the history and evolution of Magnesia Carbon Bricks, we will find the first Mag Carbon bricks were made by tar impregnating the Burnt Magneia Bricks. But now a days Magnesia Carbon bricks are no more fired and made by mixing Graphite as the source of Carbon, DBM or Fused magnesite or combination and pressed at ghigh pressure after mixing with PF Resin. By this method higher % of C can be introduced at a lesser cost and with much faster cycle time.


Tar impregnation is some thing done after pressing and curing the resin bonded bricks. Its main purpose is to remove porosity created in the process of curing, and also an attempt to increase carbon content of the brick surface. 
By my concern is that, whether it is a necessary step or can avoided, if we don't have any setup to perform such treatment.


 For most applications where MgO-C brick are used it is not necessary and is actually an exception. Some companies have applied this type of brick in very high wear areas of BOF vessels (trunnion areas). After curing most MgO-C bricks have porosity values of 4-6% so the amount of tar that you can actually get into the brick is limited.


 With addition of graphite,solid resin,liquid resin and pitch powder in magnesia carbon bricks,we already achieve low porosity.Therefore tar impregnation is not necessary for magnesia carbon bricks.

Now a days, only magnesia carbon based EAF/EBT Taphole sleeves are tar impregnated for better performance.

applicability of fused MgO (periclase) with a grain size from 0.5 to 0.001 and the content of the MgO is not more than 95%

 1) In finer fraction of batch composition of magnesia carbon bricks for ladle free board and EAF slag door application.

2) Some quantity can be mixed with coarser grains of DBM 95 to produce wet ramming mass.

3) Can be mixed with DBM ,graphite and a binder to produce slag conditioner balls for using in converter,LF,etc.

Why does magnesia carbon brick chip out ? part -2

Perhaps we can go for more details about what the chipping out looks like.

Is every vertical and every horizontal joint being eroded?

Or are there cracks developing around the circumference of the ladle?

Or is the chipping out more prevelant in one area like in the stir quadrant?


our use of 97.5% purity fused MgO and 98% purity Fused MgO suggest best in class MgO.

Also key is the purity and crystal size of the graphite. A large coarse flake graphite of intermediate purity, not necessarily the highest purity available, should offer better oxidation resistance as the impurity in the flaked graphite is SiO2 and SIO2 will provide some protection against anti-oxidants.

The particle size and amounts of anti-oxidants will affect oxidation resistance; thermal expansion and hot strength. As your ladles seem to be going cold and empty for extended periods, I would expect some addition of Al and Si to help retard oxidation of the cabon.

Construction design can also affect joint erosion as the design affects stress distribution:

Spiral construction is quickest to install but worst for structural integrity. This is especially true for ladles with poor lip ring retainers.

MiniKeys that are keyed to cloe each ring will provide a more stable lining AND they can be run to a thinner wear profile for longer life versus semi universal construction as the semi u bricks lose structural integrity when they get beyind 50% or so of the original wear profile.

The best construction is in my opinion arch brick construction. Arches have the advantage that the greatest number of joints are in the vetical dimesnsion so hoop stresses are more uniformily distributed.

In the USA, there is a trend to lower purity 96.8% fused magnesia as a cost savings - the problem with this is that there is a resulting increase in SiO2 inthe bricks and the bricks are more prone to cracking. To combat vertical cracking that occurs about every 750mm to 1000mm around the circumference, some success has been achieved by increasing the graphite levels by 2-4%.

Vertical cracks were observed in middle of many bricks. 

However,in the current ladle,after all the steps we had taken,the over all metal zone is in very good condition except chip out in 1 or 2 pockets in the purging side. 

Yes,we had chosen best fused magnesia with C/S ratio 1.9-2. 

Natural flake graphite used was of -196 grade with about 88 % passing through the 100 mesh screen.Fixed carbon tested was about 96.20 %.So,from your suggestion,it seems,we should have used -192 or -194 grade graphite. 

I carefully note down your suggestion on anti-oxidant.We had used about 1.2 % Aluminium powder and 0.8 % Silicon metal powder in slag zone bricks as the plant makes Si : Al killed steel in the ratio of 70: 30 . 

No anti-oxidant was used in metal zone and bottom bricks. 

Yes,mini key bricks 7/8 and 7/30 are used in both metal and slag zone as per customer's requirement.However,our lining expert says that due to the condition of ladle shells,7/40 would have served better in place of 7/30. 


FM 96.8 with higher carbon content is very useful.I am thinking in this direction as many customers want to buy cheaper bricks and we need to find solution.Normally 8-10 and 12-14 % final carbon are retained in metal zone and slag zone bricks.So,for lower purity FM,what % of final C you wll recommend for bottom,metal zone and slag zone bricks ? 

I have one more question.What are the advantages of using +196/+195/+194( 80 % min retained on 100 mesh screen) graphite in place of -194/-195/-196(min 80% passes through 100 mesh) in magnesia carbon bricks? 
And what are the advantages of using +895 graphite in place of + 195 graphite.I mean how larger flake lengths help in magnesia carbon bricks.I am perplexed because now people are doing research and developing bricks by using Nano graphite(3 D graphite)particles. 

 Ladle insulation , Maximum continuity , control slag , using right taphole in EAF , minimize super heat before tapping , optimize treatment time between EAF and casting , and many others from steel making side are very important for ladle life.

Why does magnesia carbon brick chip out ?

I recently observed early life (30-40 heats) cracking and chip out of magnesia carbon bricks(especially in metal zone) of 50 ton capacity ladle in a steel plant where 30-40% heats are routed thru VD and alloy steel is produced. 

I have found that plant operation is intermittent and sometimes,after every 2-3 days,a ladle is kept out of circulation and in cold condition for 8-24 hours before being heated for 3-4 hrs and brought to circulation once again.This is done to accomodate some other ladle which is in circuit.This is done on rotation basis. 

So,why this chip out is happening ? 

Is it due to expansion of the bricks ? 

Is it due to spalling ? 

Is it due to very tight refractory lining ? 

Is it due to lower residual carbon % (presently residual carbon is 10% metal zone and 14 % slag zone )? 

Does it depend on purity of magnesia (presently 97.5% FM with C/S ratio 1.7-1.9 and 98 % FM with C/S ratio 1.9 are used in metal and slag zone respectively) ? 

Can it happen due to entry of any foreign element in the batch? 

Will addition of DBM reverse the trend ? 

Will using a single 2 mm thick mortar paste between two bricks in each ring to provide expansion gap help ? 

Can it happen due to size/location of the key (piece of brick which is cut out from the mother brick and inserted to tighten each ring).I mean if keys of several rings fall in the same line,or keys are too small to get eroded and come out of the lining) or keys fall on the purging side of the lining! 

Can step formation in the lining result in faster damage of the bricks ? I have observed 10-20 mm steps between two rings in few cases in a ladle which was being lined.

Can spiral lining in place of present straight lining reduce such chip outs ? 

Is chip out a quality issue of the lining or of the product? 

Ladle Preheaters

The ladle refractory lining temperature, during the production cycle, especially for basic linings, must be constantly reset and maintained at convenient temperature values higher than 1.000°C-1.200°C. A correct management of ladle heating and temperature keeping, allows to improve the main steel making parameters:

* Low liquid steel temperture changings before and after tapping

* Tapping temperature decrease at E.A.F. (5-10°C)

* Consumption reduction of expensive energy (i.e. reduction electrical energy of the E.A.F.)

* Electrode consumption reduction of the E.A.F.

* Reduction of Tap to Tap time at E.A.F.

* Increase of E.A.F. productivity

* Guarantee of casting start in the C.C.M.

* Low ladle refractory lining consumption

* Increase of safety refractory lining performances

* Elimination of liquid steel infiltrations trough / behind the working lining

Ladle Preheaters Combustion Technology Should be :

* High efficiency gas – air burners

* High velocity and long flame burners

* Pulse firing burners or modulating burners

* Low NOx emissions of burners

* Burnes designed and manufactured with special refractory steel parts for long life time of operation

* Micro / PLC Automatic control of burners combustion ratio

* Automatic and efficient control of ladle temperature

* High preheating performances

* Extraordinary uniformity of ladle lining temperature

* Low gas consumption

* Shorter drying – preheating time

* Significant energy saving compared to usual technology

* High efficiency thermal recuperators (additonal energy saving 30%)

* Burners available for natural gas, L.P.G., Diesel oil, Coke oven gas

* Emission rates according to E.C.C. standards

* Exhaust fumes system and post-combustion system for dangerous and smoking emissions

SLITTING SYSTEMS

 Slitting process, as a rolling method, is used at rolling mills for increasing the efficiency and productivity, minimizing the number of passes, the machinery and equipment requirements and minimizing the costs.

   At conventional rolling mills, a billet is rolled through several stands and a single final product is rolled from each billet. But, in slitting process, by means of special roll pass designs and special guiding equipment, while the billet is rolled, it is slitted to two, three or four parts also. Especially for fine products, the slitting method easily doubles or quadruples the production capacity without increasing the rolling speed.

   SMM achieved very demanding results with the very successful double, triple and quadruple slitting applications, resulting with increased production capacity and reduced power consumption.

KT2000 LadleSLAG

The KT500 OnLineMOMS system integrates caster variable inputs to provide a complete monitoring system for process and mechanical/control analysis of the caster. The system consists of:

main control unit with system computer and software;

four compact sensors, which are permanently attached to the mold table;

and high temperature system cables.

TYPICALLY INTEGRATED SIGNALS

• Oscillation speed

• Casting speed

• Mold level

• Tundish temperature

• Tundish slide gate position

• Tundish weight

• Ladle weight

ADVANTAGES

• Monitor real-time casting conditions

• Evaluate variables that effect cast product quality

• Provide early indication of maintenance issues

• Compare noncasting to casting conditions

• Evaluate mold lubrication practices

MEASUREMENTS AND CALCULATIONS

• Up/Down Displacement

• Left/Right Displacement

• Front/Back Displacement

• Residual Displacement

• Phase

• Rise/Fall Ratio

• Low, Medium and High Frequency Vibrations

• Negative Strip Time and Ratio

• Positive Strip Time and Ratio

• Mold Lead

• Friction Index

• Oscillation Mark Depth

Crude steel production (million tonnes):

Crude steel production (million tonnes):

Rank	Country/Region	2007	2008	2009	2010	2011
—	World	1,351.3	1326.5	1,219.7	1,413.6	1,490.1
1	People's Republic of China	494.9	500.3	573.6	626.7	683.3
2	Japan	120.2	118.7	87.5	109.6	107.6
3	United States	98.1	91.4	58.2	80.6	86.2
4	India	53.5	57.8	62.8	68.3	72.2
5	Russia	72.4	68.5	60.0	66.9	68.7
6	South Korea	51.5	53.6	48.6	58.5	68.5
7	Germany	48.6	45.8	32.7	43.8	44.3
8	Ukraine	42.8	37.3	29.9	33.6	35.3
9	Brazil	33.8	33.7	26.5	32.8	35.2
10	Turkey	25.8	26.8	25.3	29.0	34.1
11	Italy	31.6	30.6	19.7	25.8	28.7
12	Taiwan	20.9	19.9	15.7	19.6	22.7
13	Mexico	17.6	17.2	14.2	17.0	18.1
14	France	19.3	17.9	12.8	15.4	15.8
15	Spain	19.0	18.6	14.3	16.3	15.6
16	Canada	15.6	14.8	9.0	13.0	13.1
17	Iran	10.1	10.0	10.9	12.0	13.0
18	United Kingdom	14.3	13.5	10.1	9.7	9.5
19	Poland	10.6	9.7	7.2	8.0	8.8
20	Belgium	10.7	10.7	5.6	8.1	8.1
21	Austria	7.6	7.6	5.7	7.2	7.5
22	Netherlands	7.4	6.8	5.2	6.7	6.9
23	South Africa	9.1	8.3	7.5	8.5	6.7
24	Egypt	6.2	6.2	5.5	6.7	6.5
25	Australia	7.9	7.6	5.2	7.3	6.4
26	Argentina	5.4	5.5	4.0	5.1	5.7
27	Czech Republic	7.1	6.4	4.6	5.2	5.6
28	Saudi Arabia	4.6	4.7	4.7	5.0	5.3
29	Sweden	5.7	5.2	2.8	4.8	4.9
30	Kazakhstan	4.8	4.3	4.1	4.3	4.7
31	Slovakia	5.1	4.5	3.7	4.6	4.2
-	Malaysia	6.9	6.4	4.0	4.1	N/A
32	Finland	4.4	4.4	3.1	4.0	4.0
—	Others[4]	29.8 (est.)	28.3 (est.)	23.3 (est.)	25.6 (est.)