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Control Classes

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Control Classes

          Several quality classes can be applied to the inspection of bars. The applicable quality class must be agreed between the buyer and the supplier. Tables 2 and 3 detail the registration level and acceptance criteria applicable to the three quality classes for normal probes.
 
        Table-1. Scanning Scope with Normal Probes        
        Shape Scanning Gridlines a, b % Scan a, b        
               
        Diameter D or Thickness t, mm Scan Line c        
               
        Round D ≤ 200 2 directions at 90º 100% scanning in an area of ​​at least 180º on the cylindrical surface        
               
        200 < D ≤ 400 3 directions at 60º or 120º        
               
        Tetragon t ≤ 150 1 line at 2 surface 100% scanning from two surfaces perpendicular to each other        
               
        150 < t ≤ 400 3 line at 2 surface d        
               
               
        Hexagon t ≤ 150 1 line at 2 surface 100% scanning from at least half adjacent surface        
               
        150 < t ≤ 400  1 line on at least half of the faces        
               
               
        a) Additional screening can be done if specifically specified in the inquiry or order.        
        b) 100% inspection means at least 10% overlap on consecutive probe lines.        
               
        c) For Type 1a or 1b, if the presence of a hole prevents reaching the opposite surface, the number of scan lines should be doubled symmetrically.        
               
        d) The distance between the guide lines should be equal to the wall thickness for parts up to 200 mm thick.        
               
        Manual scanning speed should not exceed 150 mm/s.        
 
  Classification of Discontinuities
  Discontinuities are classified according to ecodynamic models as follows.
a) Point Discontinuity;
  If the echodynamic pattern is less than or equal to 1 and / or a beam width of –6 dB, it is called point discontinuity.
b) Extended Discontinuity;
  If the echodynamic pattern is greater than 2 and / or the dimension –6 dB width, it is called extended discontinuity.
c) Isolated Discontinuities;
  If the distance d between points corresponding to the maximum of indications of adjacent discontinuities exceeds 40 mm, they are called isolated discontinuities.
 
d) Grouped Discontinuities;
  If the distance d between points corresponding to the maximum of indications for adjacent discontinuities is less than or equal to 40 mm, they are called grouped discontinuities.
 
 
        Table-2. Quality Classes, Registration Level and Acceptance Criteria for Ferritic and Martensitic Steel Bars        
               
        Parameters Quality Classes        
        1 2 3 4        
        Recording Level   > 8   > 5   > 3   > 2        
        Equivalent disc-shaped reflector diameter (EFBH) deq mma        
               
        The rate of decrease in rear wall echo height, R b,c   ≤ 0,10   ≤ 0,30   ≤ 0,50   ≤ 0,50        
               
        Accept conditions   ≤ 12   ≤ 8   ≤ 5   ≤ 3        
        EFBH (for isolated point discontinuities) deq mma        
               
        EFBH (for large or clustered point discontinuities) deq mma   ≤ 8   ≤ 5   ≤ 3   ≤ 2        
               
        a)   deq = Equivalent disc-shaped reflector diameter.        
        b) R = Fn / F o,n        
               
           Here;        
           For t ≥ 60 mm, n=1;        
           For t < 60 mm, n=2;        
           Fn = amplitude of the nth back wall echo (screen height)        
           F o, n = the amplitude (screen height) of the nth back wall echo in an accurate region at the same sound distance as Fn        
               
        c)   If the decrease in the height of the rear wall echo exceeds the recording level, this should be examined in more detail. The R rate is applicable only in case of a sudden decrease in reverb height due to a discontinuity.        
               
               
 
        Table-3. Quality Classes, Registration Level and Acceptance Criteria for Austenitic and Austenenoferritic Steel Bars        
               
        Bar Thickness Record Level deqa Acceptance Criteria for Isolated Point Type Discontinuities deqa Acceptance Criteria for Expanded or Grouped Point Type Discontinuities deqa        
               
               
               
               
        mm mm mm mm        
        Class 1        
        t ≤ 75 > 5 ≤ 8 ≤ 5        
        75 < t ≤ 250 > 8 ≤ 11 ≤ 8        
        250 < t ≤ 400 > 14 ≤ 19 ≤ 14        
        Class 2        
        t ≤ 75 > 3 ≤ 5 ≤ 3        
        75 < t ≤ 250 > 5 ≤ 8 ≤ 5        
        250 < t ≤ 400 > 8 ≤ 11 ≤ 8        
        Class 3        
        t ≤ 75 > 2 ≤ 3 ≤ 2        
        75 < t ≤ 250 > 3 ≤ 5 ≤ 3        
        250 < t ≤ 400 > 5 ≤ 8 ≤ 5        
        a)   deq = Equivalent diameter of the flat bottom hole.        
 
Surface Quality Class Nominal Diameter, dN*, mm Allowable Max. Of Surface Discontinuities Depth**, mm
A 5 ≤ dN ≤ 25 0,50
25 ≤ dN ≤ 150 0,02 x dN
B 5 ≤ dN ≤ 12 0,20
12 ≤ dN ≤ 18 0,25
18 ≤ dN ≤ 30 0,30
30 ≤ dN ≤ 120 0,01 x dN
C 5 ≤ dN ≤ 12 0,17
12 ≤ dN ≤ 30 0,23
30 ≤ dN ≤ 120 0,0075 x dN
D 5 ≤ dN ≤ 12 0,15
12 ≤ dN ≤ 40 0,20
40 ≤ dN ≤ 60 0,005 x dN
60 ≤ dN ≤ 80 0,30
E 5 ≤ dN ≤ 60 ***
* The maximum bar diameter is between 30mm and 60mm depending on the rolling direction. Depending on the rolling direction, wire rods are generally not rolled below 15mm.
** The depth of surface discontinuities is measured in the radial direction on the real surface of the product. Dimensional tolerances should also be taken into account when determining the cross-section of the final part, which should be free of discontinuities and imperfections.
*** This Surface quality class should be better than Class D. Specifications and inspection methods should be agreed between the parties.
NOTE-1: Regional imperfections and defects can be removed by grinding within the limits specified in the table.
NOTE-2: Resolving defects by welding can only be permitted if the customer agrees. This process should not cause deterioration in material properties (such as excessive hardening, crack formation).
NOTE-3: If the products are ordered for towing purposes, shallow discontinuities and regional repairs that cannot be destroyed by pulling are not allowed.
          Several quality classes can be applied to the inspection of bars. The applicable quality class must be agreed between the buyer and the supplier. Tables 2 and 3 detail the registration level and acceptance criteria applicable to the three quality classes for normal probes.
      Table-1. Scanning Scope with Normal Probes        
      Shape Scanning Gridlines a, b % Scan a, b        
             
      Diameter D or Thickness t, mm Scan Line c        
             
      Round – Exterior Surface D ≤ 200 2 directions with 90 ° 100% scanning in an area of ​​at least 180 ° on the cylindrical surface        
      200 < D ≤ 500 3 directions with 60 °        
      500 < D ≤ 1000 4 directions with 45 °        
      1000 < D 6 directions with 30 °        
      Square – Exterior Surface Scanning from two perpendicular surfaces on square grid lines c,d 100% scanning from two surfaces perpendicular to each other        
             
             
             
             
      Round – Head Scanning 360 ° from cylindrical surface and scanning a side surface on square grid lines d 100% scanning in an area of ​​at least 180 ° on the cylindrical surface and 100% scanning from one of the flat surfaces        
             
             
             
             
      Pipe – Exterior Surface 360 ° sweep from outer cylindrical surface on square-shaped gridlines d 100% scanning 360 ° from the outer cylindrical surface        
             
             
             
      Pipe – Head Scanning on square grid lines, 360 ° from the outer cylindrical surface and guide lines from a flat surface d Scanning 360 ° from a cylindrical surface and 100% from a flat surface        
             
             
             
      a) Additional screening can be done if specifically specified in the inquiry or order.        
      b) 100% inspection means at least 10% overlap on consecutive probe lines.        
             
      c) For Type 1 or 2, if the presence of a hole prevents reaching the opposite surface, the number of scan lines should be doubled symmetrically.        
             
      d) The distance between the guide lines should be equal to the wall thickness for parts up to 200 mm thick.        
             
      Manual scanning speed should not exceed 150 mm/s.        
 
  Classification of Discontinuities
  Discontinuities are classified according to ecodynamic models as follows.
a) Point Discontinuity;
  If the echodynamic pattern is less than or equal to 1 and / or a beam width of –6 dB, it is called point discontinuity.
b) Extended Discontinuity;
  If the echodynamic pattern is greater than 2 and / or the dimension –6 dB width, it is called extended discontinuity.
c) Isolated Discontinuities;
  If the distance d between points corresponding to the maximum of indications of adjacent discontinuities exceeds 40 mm, they are called isolated discontinuities.
 
d) Grouped Discontinuities;
  If the distance d between points corresponding to the maximum of indications for adjacent discontinuities is less than or equal to 40 mm, they are called grouped discontinuities.
 
 
      Table-2. Quality Classes, Registration Level and Acceptance Criteria for Normal Probes        
             
      Parameters Kalite Sınıfı        
      1 2 3 4        
      Recording Level   > 8   > 5   > 3   > 2        
      Equivalent disc-shaped reflector diameter (EFBH) deq mma        
             
      The rate of decrease in rear wall echo height, R b,c   ≤ 0,10   ≤ 0,30   ≤ 0,50   ≤ 0,50        
             
      Accept conditions   ≤ 12   ≤ 8   ≤ 5   ≤ 3        
      EFBH (for isolated point discontinuities) deq mma        
             
      EFBH (for large or clustered point discontinuities) deq mma   ≤ 8   ≤ 5   ≤ 3   ≤ 2        
             
      a)   deq = Equivalent disc-shaped reflector diameter.        
      b) R = Fn / F o,n        
             
         Here;        
         For t ≥ 60 mm, n=1;        
         For t < 60 mm, n=2;        
         Fn = amplitude of the nth back wall echo (screen height)        
         F o, n = the amplitude (screen height) of the nth back wall echo in an accurate region at the same sound distance as Fn        
             
      c)   If the decrease in the height of the rear wall echo exceeds the recording level, this should be examined in more detail. The R rate is applicable only in case of a sudden decrease in reverb height due to a discontinuity.        
             
             
 
      Table-3. Quality Classes, Recording Level and Acceptance Criteria for Transverse Wave Probes When Working with DGS Charts Prepared According to Disc Shaped Reflectors        
             
             
      Quality Class Record Level deqa Acceptance Criteria for Isolated Point Type Discontinuities deqa Acceptance Criteria for Expanded or Grouped Point Type Discontinuities deqa        
             
             
             
      mm mm mm        
      1        
      2 > 5 ≤ 8 ≤ 5        
      3 > 3 ≤ 5 ≤ 3        
      4 > 2 ≤ 3 ≤ 2        
      a)   deq = Equivalent diameter of the flat bottom hole.        

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