Indra Udyog

Calorised Lancing Pipes

Calorised lance pipes are prepared by rendering Calorising finish to carbon steel in a thickness of 100-150 microns on both inner and outer surface. This is a aluminum diffusion treatment which promotes the fireproof properties of steel pipes. This diffusion is an intermetallic bond, which doesn’t get damaged either by mechanical working like bending or straightening or by high temperatures. In the case of ceramic coated pipes, oxidation takes place at that part of the surface in contact with the liquid metal. In the case of Calorised pipes, the metal existing at the surface of the diffused zone is oxidized to its respective oxide, which prevents the further progress of oxidation and also melting. Hence diffused, aluminum is oxidized to alumina, which has very high melting pint such as 20500C compared to the melting point of aluminum, which is 6580C.

This is the essential difference between ceramic coated pipes and joint Calorised pipes. A more effective result is obtained by ceramic coating on the metal diffused zone.

Casella di testo: Diffused Calorised layer - 100 to 150 microns Base Pipe Diffused Calorised layer - 100 to 150 microns
 


In the process of steel manufacturing by electric furnace, the consumption rate of lance pipes for oxygen injection show rather high ratio to high temperature and severe oxidation. In general, steel pipes are used as lance pipes for oxygen / carbon injection. If MS pipes are treated by this Calorised process, consumption rate of lance pipes will improve 6-7 times. The advantages of oxygen steel making process are:
  • The exothermic reaction and agitation promote decarbonisation and heat rise in the furnace, while foaming slag can be eliminated.
  • Fusion of sub material can be accelerated
  • Quality of steel will be improved.
  • As the process raises the temperature of furnace, it leads to saving in electric power.
  • Selection of raw materials to be charged becomes easy.
  • The process raises the production capacity of an electric furnace.
  • Hydrogen, Nitrogen and non-metallic inclusions can be eliminated through oxidation.
  • It makes it possible to recover chrome with the use high chrome steel scrap.

Hence oxygen lancing is a must in steel making. Efficient lancing makes cleaner and cheaper steel. Therefore a Calorised pipe for oxygen lancing is the most efficient and simple alternative to achieve the above advantage.

Besides there are industrial advantages:

Lower Down Time
As infrequent replacement is required the down time is reduced directly by 6 times. This brings a minimum savings of 15 mins. Per heat and at 17/18 heats a day it translates into 255 mins., ie. 4.25 hrs/day . This is equal to 600 hrs/year.

This saving of 600 hrs/years gives the following,

  • Savings in Electricity Cost equivalent to 1326 hrs/year.
  • Savings in Labour Cost  1326 hrs/year.
  • Higher yield equivalent to 1326 hrs/year.
  • Lower Inventory Cost.
  • Lesser space for storage of Calorised Lancing Pipes.  

Therefore it is prudent to use Calorised Pipes for Lancing especially in the charged scenario of the open economy where for any industry to survive in competition it is necessary to increase efficiency, quantity and decrease costs.

Comparison Chart Between Mild Steel Pipe & Calorised Pipe for oxygen lancing under same condition of oxygen pressure and flow rate,

Case

Oxygen Pressure

Press Kg/cm2

Oxygen flow

Rate

m3/min

Charge time

min

Length of

Consumption

Mm

Consumption

Rate mm/min.

Type of

Pipe

Ratio of Mild Steel Calorised

Pipe

I

6.5-7

6.5-5

3

1950

650

Mild Steel

1

6.5-7

6.5-5

15

1290

86

Calorised

7.56

6.5-7

6.5-5

15

1420

94

Calorised

6.91

II

6

6

3

2430

809

Mild Steel

1

6

6

10

1150

115

Calorised

7.03

6

6

10

890

89

Calorised

9.03

III

5.5-6

5.5

3

1860

620

Mild Steel

1

5.5-6

5.5

10

840

84

Calorised

7.38

5.5-6

5.5

10

1070

107

Calorised

5.79

IV

6.6

6.3

3

1830

610

Mild Steel

1

6.6

6.3

10

610

61

Calorised

10

6.6

6.3

10

1070

107

Calorised

5.70

Method of Usage

It is considered ideal to fix a Calorised lancing pipe to a lifting hook or stand or an automatic manipulator and insert it through the sight hole on the door at an angle of 250C to 300C to the surface of molten steel and hold the end of pipe at a depth of 150mm below the slag. Oxygen or carbon can then be injected, controlling the pressure, flow rate and the injection rate of pipes.

  Availability & Size

Pipes are available in threaded or plain end. Threaded ends are fixed with one coupling and one PVC cap. The Pipes are packed in HDPE bags.

Diameter

OD mm

Wall Thickness

Mm

Length

m

13.2

1.8

5.5 / 6

17.2

1.8

5.5 / 6

21.3

2.0

5.5 / 6

26.0

2.35

5.5 / 6

32.2

2.5

5.5 / 6

42.0

2.5

5.5 / 6

48.0

2.5

5.5 / 6

Packing Details

Sr. No.

Size NB

No of Pipes

/ Pack

Nos.

Approx. Weight of Pack

Kgs

1

13.2

25

69.00

2

17.2

15

56.00

3

21.3

10

52.00

4

26.0

5

38.00

5

32.2

5

50.00

6

42.0

3

40.00

7

48.0

3

46.00

 

  Calorising

Calorising is a metallurgical process for treating the surface of steels, stainless steels and alloy steels, with either aluminium, aluminium silicon, chromium or boron. The treatment provides protection against elevated temperature scaling and corrosion. Indra Udyog has developed its process based on aluminium silicon alloy.

Adding aluminium to carbon and stainless steels is commonly known to improve corrosion resistance. A side effect of the process, however is, unfavourable changes in the mechanical properties of the base steel.

Calorising solves this problem. Calorising diffuses the aluminium alloy into the steel surface to form an alloy with excellent heat and corrosion resistant properties, retaining the base steel’s inherent strength and rigidity, without changing the high temperature mechanical properties of the base steel. The protection provided by the calorised diffusion zone remains effective at all temperatures upto the boiling point of the base metal.


During the calorising process, the steel is chemically cleaned, treated with flux at 700C, further treated with another flux at 7300C and then dipped into molten aluminium alloy at 7700C. This results in an evenly aluminium coated steel. This then positioned in a retort. The retort is sealed and placed in an atmosphere controlled furnace. After the heat treatment, the aluminium alloy diffuses into the surface of the steel, at the elevated temperature, forming an aluminide within the surface of the steel. This aluminide layer is called the diffused layer. It is totally inert to most corrosive chemicals and gases.

After cooling in the furnace, the treated steel is taken out of the retort. Straightening, trimming, beveling and other secondary operations are performed.

Process quality is monitored by test coupons. The coupons are of the same specification as the base steel. These are placed along with the process materials in the retort. The nature of the process, air controlled atmosphere and uniform programmed heating ensures uniform calorising over the whole surface of the process steel including the test coupons. After the process is completed the coupons are removed from the retort, sectioned and examined in the laboratory for quality and depth of diffusion. As the process is a batch process, it is fair to assume that the results of the coupons are a fair assessment of the quality of the whole batch. Different applications may require different depths of diffusion. The customer may set his own standards within the diffusion limits achievable. Higher the diffusion, does not necessarily mean that, higher will be the safety, but will surely be higher cost.

The end result of the calorising process is a true aluminde with the base steel. The process is not a coating and there is no mechanical interface with the substrate. This layer is not visible to the naked eye. It can only be observed under magnification. The protective diffusion zone cannot be removed except by a machining operation.

Calorising is used to enable engineered materials to better resist high temperature sulfidation, oxidation, carburization, scaling and hydrogen permeation. All types of wrought and cast steels, plain carbon and low alloy carbon steels, ferritic and austenitic stainless steels can be calorised. Temperature and process materials determine the specifications of the steel to be used for calorising.

The calorising process as described above is unique in its approach. Conventially pack cementation and out of pack gas calorising  has been followed by some manufacturers. These processes are fraught with extreme dangers and are unreliable for long and complex parts, such as small diameter tubes 6m and above. Indra Udyog’s process overcomes all these drawbacks and gives a much higher and reliable product. The process patent has been applied for.

Salient Features of Calorising.

Advantages over Coatings

  • Elimination of problems inherent in coating processes due to difference in the thermal expansion coefficient between the coating and the substrate.
  • Ease with which fabricated shapes, internals, long tube internals and complex contours can be treated. Line of sight is not required.

Technical & Commercial Benefits

  • High Corrosion resistance
  • Diffusion depth upto 300 microns.
  • Continuous operation upto 9000C
  • Inherent properties of the base steel are unaffected and retained.
  • High Life, lower maintenance and higher efficiency.
  • Lower down times
  • Increases tube life upto about 20 years
  • Cheaper in the longer run.

Common Applications

  • Fertilizer: Sulphuric acid/ Phosphoric acid equipment, gas ducts for SO2
  • Refining : Recuperators, charge heaters, sour gas treaters, sulphur recovery plants and heat exchangers.
  • Petrochemical : Reformers, distillation columns, ammonia heat exchangers, pipelines.
  • Boilers: Pulp and Paper boilers, waste heat recovery boilers, fluidized bed boilers
  • Steel : Lancing pipe, water wall panels
  • Nuclear : Low Hydrogen Permeation heat exchangers.
  • Sugar : Refining Section Piping, Air heaters  

Stainless Steel and Calorised Steel

  • Calorised steel out performs stainless steels in high temperature and corrosive environments
  • Stainless steels are often considered the final answer to every kind of corrosion problem.
  • Austenitic Stainless Steels are used because they offer excellent resistance to high temperature oxidation. Generally higher the temperature of exposure, higher the nickel content of the steel. Stainless steel 201 (16/18% Nickel) can withstand a continuous temperature of 8500C, while Stainless steel 310 ( 19/22% Nickel) can withstand temperatures as high as 11500C.
  • Higher the nickel, higher are the chances of high temperature sulfidation. Nickel preferentially combines with sulphur to create a low melting temperature nickel sulphide eutectic. The melting temperature of this eutectic is 6450C
  • At temperature as low as 5500C Sulphur will begin to penetrate towards the nickel in the steel, causing rapid