High-strength deformed steel bars and wires for concrete reinforcement

IS 1786 Scope: Key Specifications & Tables

• Nominal Sizes (Clause 6.1):
  4, 5, 6, 8, 10, 12, 16, 20, 25, 28, 32, 36, 40, 45, 50 mm
  (Other sizes by mutual agreement)

• Cross-Sectional Area & Mass (Table 1):

• Effective Cross-Sectional Area (Clause 6.3.1):
  [ A = \frac{W}{0.00785 \times L} ]
  where,
  (W) = mass in kg (±0.5%),
  (L) = length in m (±0.5%)

• Mechanical Properties (Table 3):
  Yield stress ranges from 415 to 600 N/mm² depending on grade (Fe 415 to Fe 600).
  TS/YS ratio ≥ 1.06 to 1.25; elongation minimum varies from 10% to 20%.

• Mandrel Diameter for Bend Tests (Clause 9.4.1):

IS 1786 Key References:

1. Nominal Sizes, Cross-Sectional Area & Mass (Clause 6.1, Table 1)

2. Effective Cross-Sectional Area Calculation (Clause 6.3.1)

[ \text{Gross cross-sectional area (mm}^2) = \frac{W}{0.00785 \times L} ]

• W = mass in kg (±0.5%)
• L = length in meters (±0.5%)

3. Mechanical Properties of High Strength Deformed Bars (Clause 8.1, Table 3)

IS 1786: Definitions & Key Specifications

1. Effective Cross-Sectional Area (Clause 6.3.1)

For uniform deformation bars/wires: [ A_{effective} = 0.00785 \times \frac{W}{L} \quad (\text{in } mm^2) ]

• W = mass in kg (±0.5%)
• L = length in m (±0.5%)

2. Nominal Sizes, Cross-Sectional Areas & Mass (Clause 6.1 & Table 1)

Other sizes available by mutual agreement.

3. Mechanical Properties (Table 3, Clause 8.1)

4. Mandrel Bend Test Diameter (Clause 9.4.1)

| Nominal Size (mm) | Max Mandrel Dia for Fe 415/500 | Max Mandrel Dia for Fe

IS 1786: Manufacture & Chemical Composition Key Points

1. Chemical Composition Limits (Max %)

2. Carbon Equivalent (CE) for Weldability

• With microalloys/low alloys:

[ CE = C + \frac{Mn + (Cr + Mo + V)}{5} + \frac{Ni + Cu}{15} \leq 0.53% ]

• Without microalloys/low alloys:

[ CE \leq 0.42% ]

Bars with CE > 0.42% require welding precautions (use low hydrogen electrodes).

3. Microalloying Elements

• Total Nb, V, B, Ti ≤ 0.30%
• Manufacturer must certify content.

4. Low Alloy Steel

• Alloy elements (Cr, Cu, Ni, Mo, P) total ≥ 0.40%
• P ≤ 0.12% if used
• If P > 0.12%, C ≤ 0.15% and other restrictions relaxed.

5. Nitrogen Content

• Max N = 0.012%
• Up to

IS 1786: Mechanical Properties & Bond Requirements Summary

Mechanical Properties (Clause 8.1 & Table 3)

• Tensile tests on bars ≥28 mm allow machining deformations only; properties calculated on actual area (Clause 9.1.2.1).
• Effective cross-sectional area per Clause 5.3 is used for calculations.

Bond Requirements (Clause 5.7)

• Bond strength (pull-out test per IS 2770 Part 1) for deformed bars must exceed plain bars by:
  • 40% at 0.025 mm slip
  • **80% at 0.

IS 1786: Nominal Sizes and Mass

Key Specifications:

• Nominal Mass (Clause 3.6):
  Mass per meter = Cross-sectional area × Density
  Density = 0.00785 kg/mm³

• Nominal Mass Calculation:
  [ \text{Nominal Mass (kg/m)} = \text{Area (mm}^2) \times 0.00785 ]

• Nominal Cross-sectional Area & Mass:
  Given in Table 1 (not provided here), typically based on bar diameter.

Tolerances on Nominal Mass (Table 2, Clauses 6.2 & 7.2.2):

Summary:

• Use 0.00785 kg/mm³ as steel density.
• Nominal mass depends on cross-section and length.
• Tolerances tighten with increasing bar size.
• Coiled bars have slightly different individual sample tolerances.

flowchart TD
    A[Nominal Diameter] --> B[Cross-sectional Area]
    B --> C[Nominal Mass = Area × 0.00785 kg/mm³]
    C --> D[Tolerance Applied per Size Category]
    D --> E{Batch / Individual / Coil}

This ensures quality control in steel reinforcement mass for structural reliability.

IS 1786: Tolerances on Nominal Mass (Clause 7.2.2 & Table 2)

• Tolerances apply to nominal mass per meter of bars/wires unless otherwise agreed.
• For bars/wires with effective cross-section per 6.3.2(b), nominal mass = gross mass; Table 2 tolerances apply.

Table 2: Tolerances on Nominal Mass (%)

¹ Single sample from batch not considered individual sample.
² For coils, batch tolerance not specified.

Key Notes:

• Nominal mass and cross-sectional area per Table 1 (Clause 6.2).
• Tolerance ensures quality control of steel bars/wires mass.
• Use these tolerances in acceptance criteria during inspection.

flowchart LR
    A[Nominal Mass per Meter] --> B{Nominal Size (mm)}
    B -->|≤10| C[Apply ±7% Batch Tolerance]
    B -->|10 < size ≤ 16| D[Apply ±5% Batch Tolerance]
    B -->|>16| E[Apply ±3% Batch Tolerance]
    C --> F[Individual Sample: Not specified]
    D --> G[Individual Sample: -6%]
    E --> H[Individual Sample: -4%]

Use these tolerances for quality checks during manufacturing and procurement.

IS 1786: Mechanical Tests - Key Formulas & Specifications

1. Test Types Referenced

• Tensile Test: IS 1608 (ISO 6892)
• Bend Test: IS 1599 (ISO 7438 & 15630-1)
• Re-bend Test: IS 1786 (ISO 15630-1)

2. Sample Preparation (Clause 9.1.2.1)

• For bars ≥ 28 mm diameter, machine the deformation zone only.
• Calculate physical properties based on the actual cross-sectional area after machining.

3. Mechanical Properties (Table 3, Clause 8.1)

• Tensile strength is typically ≥ 10% above yield stress, but not less than the specified minimum.
• % Elongation is measured on gauge length ( L_0 = 5.65 \sqrt{A} ), where ( A ) = cross-sectional area.

4. Key Formula for Tensile Strength Calculation

[ \sigma_t = \frac{P_{max}}{A} ]

• ( \sigma_t ) = Tensile strength (N/mm²)
• ( P_{max} ) = Maximum load (N)
• ( A ) = Actual cross-sectional area (mm²) after machining

Summary Diagram: Mechanical Test Flow

flowchart TD
    A[Sample

IS 1786: Selection and Preparation of Test Samples

Key Clauses:

• Clause 9.1: Sample selection follows IS 2062 unless otherwise specified.
• Clause 9.5:
  • If a test piece fails, select 2 additional samples.
  • If both pass, material passes.
  • If either fails, material fails the test.

Sample Preparation (Clause 9.1.2.1):

• For bars ≥ 28 mm diameter, only the deformations are machined for tensile, proof stress, and elongation tests.
• Calculate physical properties using the actual machined cross-sectional area.

Mechanical Properties Table Extract (Clause 8.1):

Summary:

• Test pieces must be representative and prepared as per IS 2062.
• Use actual cross-sectional area for properties calculation after machining.
• Follow retest protocol on failure: 2 additional samples.
• Maintain test records and supply certificates with material.

flowchart TD
    A[Select Initial Test Sample] --> B{Pass Test?}
    B -- Yes --> C[Material Complies]
    B -- No --> D[Select 2 Additional Samples]
    D --> E{Both Pass?}
    E -- Yes --> C
    E -- No --> F[Material Does Not Comply]

IS 1786: Inspection and Testing - Key Points

1. Sampling & Retesting (Clause 9.5)

• If the first test piece fails, two additional samples are tested.
• If both additional samples pass, material passes.
• If either fails, material fails the test.

2. Routine Inspection & Testing (Clause 10)

• All materials must undergo routine tests by manufacturer/supplier.
• Test records must be maintained and available for purchaser inspection.
• For supplied materials, a test certificate with all results must be provided.

3. Test Specimens & Methods (Clause 11)

• Frequency of bond tests (Clause 5.7) to be agreed upon between manufacturer & purchaser.

4. Delivery & Testing Facilities (Clause 12)

• Inspection/testing facilities and supply requirements follow IS 1387 unless specified otherwise.

Summary Diagram: Inspection & Testing Flow

flowchart TD
    A[Select 1st Test Piece] --> B{Pass?}
    B -- Yes --> C[Material Accepted]
    B -- No --> D[Select 2 Additional Samples]
    D --> E{Both Pass?}
    E -- Yes --> C
    E -- No --> F[Material Rejected]

Keep records, comply with IS 1387 for facilities, and ensure certificates accompany supplied materials.

IS 1786: Selection of Test Specimens - Key Points

1. Frequency of Test Specimens (Clause 11.1)

• Specimens are cut randomly from each size of finished bars/wires.
• Tests include nominal mass, mechanical properties, bend and rebend tests.

2. Retesting Procedure (Clause 9.5)

• If a test specimen fails, select 2 additional samples for the failed test.
• If both pass, the batch complies.
• If either fails, the batch is rejected.

3. Machining for Tensile Tests (Clause 9.1.2.1)

• For bars ≥ 28 mm diameter, machine only the deformations.
• Calculate properties based on actual cross-sectional area after machining.

4. Mechanical Properties (Table 3, Clause 8.1)

5. Relevant IS Standards for Testing

flowchart TD
    A[Finished Bars/Wires] --> B[Random Sampling]
    B --> C{Quantity per Cast}
    C -->|<100 tonnes| D[2 Specimens]
    C -->|≥100 tonnes| E[3 Specimens]
    D --> F[Tests: Mass, Mechanical, Bend,

IS 1786: Delivery, Inspection, and Testing Facilities - Key Points

• Frequency of Bond Test (Clause 5.7):
  As agreed between manufacturer and purchaser/testing authority.

• Testing Procedure for Failures (Clause 9.5):

  • If the first test piece fails, test two more samples.
  • If both pass, material complies.
  • If either fails, material does not comply.

• Routine Inspection & Testing (Clause 10):

  • Manufacturer must perform routine tests per IS 1786.
  • Maintain test records available for purchaser inspection.
  • Certificate of test results must accompany delivered material.

• Selection of Test Specimens (Clause 11 & 12):

  • Follow IS 1387 for general supply, inspection, and testing requirements.
  • Material cannot be dispatched without purchaser certification or Standard Mark on bundles.

Summary Table: Testing & Certification Process

flowchart TD
    A[Select First Test Piece] --> B{Pass?}
    B -- Yes --> C[Material Accepted]
    B -- No --> D[Test Two More Samples]
    D --> E{Both Pass?}
    E -- Yes --> C
    E -- No --> F[Material Rejected]

This ensures quality control and compliance with IS 1786 standards for high strength deformed bars.

IS 1786: Identification and Marking Summary

Identification & Marking (Clause 13.3 & 13.3.1)

• Bars/wires must have identification marks (brand name, trademark) introduced during rolling.
• Marks should not affect the bar's performance.
• Marks indicate the manufacturer or brand.

Manufacturer's Certificate (Clause 12.4)

Certificate must include:

• Place of manufacture
• Nominal diameter
• Grade of steel
• Rolled-in marking
• Cast/heat number
• Date of testing
• Mass of tested lot
• Individual mechanical & chemical test results

Nominal Sizes & Mass (Clause 6.1)

Mechanical Properties (Table 3, Clause 8.1)

IS 1786: Controlled Cooling Process Overview

• Applicability: Controlled cooling is an optional manufacturing step after hot rolling, used to enhance mechanical properties (Clause 1.3, 4.1.3).
• Purpose: Achieves higher strength and elongation by refining microstructure without cold twisting.
• Process: Bars are cooled at a controlled rate immediately after hot rolling, avoiding rapid quenching or slow air cooling.
• Manufacturer's Discretion: The standard allows manufacturers freedom to use controlled cooling or other processes to meet performance criteria.

Key Points from Annex A (Informative):

• Controlled cooling produces micro-alloyed steel with improved tensile strength and ductility.
• Cooling rates are optimized to prevent coarse grain formation.
• Typical mechanical properties achieved:
  • Yield Strength: Up to 500 MPa or more.
  • Elongation: Minimum 12-14% depending on grade.

Typical Mechanical Properties Table (Indicative):

Process Flow (Simplified):

flowchart LR
    A[Hot Rolling] --> B[Controlled Cooling]
    B --> C[Cold Working (optional)]
    C --> D[Final Steel Bars]

Summary: IS 1786 permits controlled cooling as a key process to improve high strength deformed bars' mechanical properties, with manufacturer flexibility on process parameters to meet specified grades.

IS 1786: Committee Composition & Related Specifications

Committee Composition (Annex B)

• The Concrete Reinforcement Sectional Committee, CED 54, includes representatives from key organizations such as:
  • Ministry of Shipping, Road Transport and Highways (Chairman: Shri G. Sharan)
  • Steel Plants (SAIL: Bhilai, Durgapur)
  • Research Institutes (CBRI Roorkee, CRRI New Delhi)
  • Construction Industry, Steel Development Associations, and others
• This multi-disciplinary committee ensures comprehensive standard formulation.

Key Specifications & Tables Related to Committee Work (from IS 1786)

Carbon Equivalent (CE) Formula for Weldability

[ \text{CE} = C + \frac{Mn + (Cr + Mo + V)}{5} + \frac{(Ni + Cu)}{15} ]

• Max CE:
  • 0.53% when microalloys/low alloys are used
  • 0.42% without microalloys (welding precautions required if exceeded)

Notes on Microalloying & Low-Alloy Steel

• Total microalloying elements (Nb, V, B, Ti) ≤ 0.30%
• Low