J.SONS COMPANY LTD.

 

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QUALITY ASSURANCE OF MATERIALS FOR FABRICATION OF BRIDGE GRIDERS, BEARINGS GIRDERS, BEARINGS AND STEEL SLEEPERS IN J.SONS COMPANY LTD., MEERUT

 

Quality assurance for each type of steel is describe below :-

 

CASTING : The process of casting consists of steel making in Electric Are Furnace. It consists of pattern making sand and core preparation for moulding Closing of moulds, pouring knocking out of  the casting strict supervision and quality control exercise is essential at all the stages to ensure specified chemistry , mechanical properties as well as soundness of  the casting . The compositions are checked before and after pouring  to ensure specified Grade and Quality.  Cheek on teaming temperature is required to get the exact fluidity of the liquid steel. Sufficient  locking of mould boxes with heavy weight are ensured to avoid liquid metal burst due to huge hydrostatic pressure inside the mould the a casting offer being cooled are knocked out of the mould  and the ingots, risers and feeders are OXY-cut and then cleaned by pneumatic chippers. The casting is thereafter placed for visual examination to the inspecting Authority which includes checking for casting defects like below holes, send inclusion metal- shortness, porosity, cracks etc., including checking of the cast – on identification marks on the casting as well as  the integral test pieces. The cast on marks consist of  casts-serial number and type date of cast and Firms insignia . All these observation permitted for next stages operation i.e. heat treatment of the casting along with the integral test block.

 

The casting is then subjected to normalising  beat  treatment  cycle in oil –fired furnace having along the time period as recovered . The heating  cycle along the time period as recorder  is processed to the inspection Authority along with the casting with integrated test-below . The Inspection Authority once more examines the casting visually and records defects (if any) with the proper measurement in the format as shown in  Annexure “C/2” and detach the integral test block after tamping for caring out the various test as per IS: 1030 and records in the format. The casting is considered for rectification ( is necessary) by  welding taking into account of size , location and depth of defects. A procedure for such rectification of defect by metal –are welding has to be followed  (Annexure “C/3”) the test blocks result recorded in the format  and if it statistics the composition and properties the casting is allowed  for proof matching.

 

After the proof matching of the casting ultrasonic testing is carried out to ensure freedom from internal defects like cracks, shrinkage etc. The results are recorded in the format . The acceptance level of    ultrasonic testing for the casting under consideration  is as per IS: 9565 level –3 and on satisfying the requirement the casting is finally accepted for final machining and fabrication of the bearing set. All the rectification to be done before ultrasonic test.

 

QUALITY ASSURANCE FOR FORGING : The forgings are made from steel ingot / blooms ensuring a forging ratio of 4:1 and 1:8:1 for ingot /bloom respectively .      The mill certificate as obtained with the supply of ingot material are checked for their correct composition . All the rollers are dame in steam operated open forging hammer at the Units. The rough forget rollers are subjected to normalising the treatment cycle in oil – fried furnaces having temperature and heat cycles recorders.  Heat- treated roller is stamped b the Inspecting Authority at one end-face of the roller for making test-pieces for mechanical tests and composition analysis . After satisfying the required properties these are permitted for Proof – machining and the test data recorded in stage.

 

After the proof–matching operation the forged rollers are subjected to ultrasonic tests to ascertain the absence t he internal flaws like cracks, hydrogen fishers pipes etc. which are extremely harmful for load-bearing  component  in bridge structure and keeping his aspect in view a suitable ultrasonic test standard and acceptance level has been prepared.

 

MILD STEEL : The mild steel used in the bridge bearings shall conform to IS: 226 and is:2062, and should be WELDABLE STRUCTURAL STEEL , Such steel shall be manufactured by open hearth electric, reflex basic oxygen or a combination of these processed and shall be free from all defects e.g. surface flexes, lamination flaws, rough /Jagged and imperfect edges and all other harmful defects. 

 

WELDING : Welding operation on the plates for manufacturer of the components involve following steps :

 

Ø      Cutting / shearing of the plates.

Ø      Edge preparation.

Ø      Manufacture of proper jigs and fixtures to take care of distortions.

Ø      Selection of proper electrode and welding parameters.

Ø      Maintaining proper pre-welding, post-welding and inter-pass temperatures.

Ø      Cleaning the weld-metal regularly to ensure freedom from entrapped inclusions / slags.

Ø      Stress relieving.

 

The most important aspects of quality control in the welding methodology can be broadly classified in the following three groups :-

 

a)     Control before starting welding

b)     Control during welding

c)     Control after welding

 

Prior to welding it is essential to ensure that edge preparation is proper and commensurate with the thickness and material of the steel plate. The electrode quality and size should be chosen properly and should be dried before use. For bridge bearing components, it is preferable to use low hydrogen electrodes so that radiographic quality of weld are produced. During welding, it is essential to maintain proper amperage and polarity and welding should be accomplished by an experienced welder who has been duly approved and certified for carrying our quality welds. This is a very important point since welds are the areas which are most susceptible to have defects and a lot can be contributed by the welder himself. It is essential to maintain proper pre-heating and inter-pass temperatures and removal of the slag after each run.

 

After the welding, it is essential to provide a thorough dressing operation and stress-relieving operation to take care of any locked-up stresses. The quality of the welds can be evaluated by the following routine tests.

 

a)     Macro etching tests

b)     Ultrasonic / radiographic examination.