Rate analysis for structural fabrication

Great — let’s dive into rate analysis for structural fabrication.

🔧 What Is Rate Analysis in Structural Fabrication?

Rate analysis is the detailed computation of the cost per unit (usually per ton or per square meter) for fabricating structural steel. It includes materials, labor, consumables, equipment, and overheads.

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🧮 Sample Structural Fabrication Rate Analysis (Per Metric Ton)

Component Unit Qty Rate (INR) Amount (INR)

1. Labor (fabrication) Man-hours/ton 90 100 9,000

2. Welding electrodes Kg/ton 8 300 2,400

3. Gases (O₂ + DA) m³/ton 6 150 900

4. Power consumption kWh/ton 50 10 500

5. Machinery usage per ton - 1,500 1,500

6. Paint / surface prep per ton - 800 800

7. Bolts / fittings per ton - 600 600

8. Overhead & profit % of subtotal 15% - 2,238

Total 17,938

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⚙️ Notes:

Rates vary based on project size, region, and fabrication complexity.

Labor productivity depends on plate thickness, joint type (butt/fillet), and workshop conditions.

For site fabrication, costs will be 15–25% higher due to logistics and handling.

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🧰 Typical Productivity Norms:

Activity Productivity (per day per person)

Manual SMAW welding 1.5 to 2.5 m/hr

Assembly & fitting (heavy) 0.8–1.2 MT/day

Oxy-acetylene cutting 1–2 m/hr (20mm plate)

Grinding & finishing 8–10 m²/day

Selecting the appropriate argon gas mixture for welding

 Selecting the appropriate argon gas mixture for welding involves considering the type of welding process, the materials being welded, and the desired weld characteristics. Here's a step-by-step guide to help you choose the right argon gas or argon gas mixture for your welding needs:

1. Identify the Welding Process

Different welding processes may require different gas mixtures:

• GMAW (MIG/MAG Welding): Commonly uses argon or argon-based mixtures.
• TIG Welding: Typically uses pure argon for most metals.
• Plasma Arc Welding: Often uses argon as a primary gas, sometimes with hydrogen or helium added.

2. Determine the Base Material

The material you are welding significantly influences the choice of gas:

• Mild Steel: Often welded with a mixture of argon and CO2 (e.g., 75% Argon, 25% CO2) or argon and oxygen.
• Stainless Steel: Typically uses argon with small additions of oxygen or CO2 (e.g., 98% Argon, 2% CO2) to stabilize the arc and improve penetration.
• Aluminum: Pure argon is usually preferred, though argon-helium mixtures can be used for thicker sections to improve heat input and weld quality.
• Copper and Nickel Alloys: Pure argon or argon-helium mixtures can be used.

3. Assess the Desired Weld Characteristics

Consider the specific requirements of your weld, such as:

• Penetration: Adding CO2 or helium can increase penetration.
• Arc Stability: Small amounts of oxygen can improve arc stability.
• Weld Appearance: Pure argon tends to produce cleaner welds, especially on non-ferrous metals.
• Spatter Levels: Argon-based mixtures generally produce less spatter compared to pure CO2.

4. Select the Gas Mixture

Based on the above factors, choose an appropriate gas mixture:

• Pure Argon (100% Ar): Commonly used for TIG welding and MIG welding of non-ferrous metals like aluminum and copper.
• Argon-CO2 Mixture (e.g., 75% Ar, 25% CO2): Widely used for MIG welding of carbon steel and provides good penetration and arc stability.
• Argon-Oxygen Mixture (e.g., 98% Ar, 2% O2): Used for MIG welding of stainless steel to improve arc stability and reduce spatter.
• Argon-Helium Mixture (various ratios): Used for materials requiring higher heat input, such as thicker aluminum or copper.

5. Check Gas Availability and Cost

Ensure the selected gas mixture is readily available and consider the cost, as some mixtures may be more expensive or harder to source than others.

6. Test and Optimize

Before starting your project, test the selected gas mixture on a sample piece to ensure it meets your requirements for weld quality, appearance, and mechanical properties. Adjust welding parameters as needed:

• Voltage and Amperage: Fine-tune to match the gas mixture and material thickness.
• Wire Feed Speed: Adjust to control deposition rate and penetration.
• Travel Speed: Balance to avoid defects such as porosity or burn-through.

Example Procedures for Common Scenarios

• MIG Welding Mild Steel:

  1. Select a 75% Argon / 25% CO2 mixture.
  2. Set appropriate welding parameters (e.g., 18-22 volts, 200-300 inches per minute wire feed speed).
  3. Test on a sample piece, adjusting settings for optimal results.

• TIG Welding Aluminum:

  1. Use 100% pure argon.
  2. Set the AC balance and frequency for your TIG welder.
  3. Test weld and adjust amperage and travel speed as needed.

By following these steps, you can select the appropriate argon gas mixture for your specific welding needs, ensuring high-quality and efficient welding operations.

E70s-2 welding wire Gas Metal Arc Welding (GMAW)

 The E70s-2 is a classification of welding wire used in Gas Metal Arc Welding (GMAW) and is a part of the American Welding Society (AWS) specifications. Here's a breakdown of what E70s-2 stands for:

• E: Electrode (or filler metal).
• 70: Indicates a tensile strength of 70,000 psi.
• S: Solid wire (as opposed to flux-cored wire).
• 2: Indicates the chemical composition of the wire, specifically the deoxidizers used.

The E70s-2 welding wire is characterized by its triple deoxidized composition, meaning it includes elements like aluminum, titanium, and zirconium in addition to manganese and silicon. This combination makes it suitable for welding over rust, mill scale, or slightly contaminated surfaces, providing good performance in less-than-ideal conditions.

Here are some of the key features and benefits of E70s-2 welding wire:

1. Versatility: Can be used in a variety of applications, including automotive, structural, and general fabrication.
2. Good for Out-of-Position Welding: Suitable for all position welding (flat, horizontal, vertical, overhead).
3. High Deposition Rates: Efficient in terms of material usage and welding speed.
4. Smooth Weld Bead Appearance: Produces welds with a smooth bead appearance, reducing the need for post-weld cleaning.
5. Good Mechanical Properties: Provides good tensile strength and impact resistance.

Common Applications

• Construction: Suitable for structural steel projects.
• Automotive Industry: Used for welding vehicle parts and assemblies.
• General Manufacturing: Applied in the fabrication of machinery, tools, and other industrial components.

Usage Tips

• Shielding Gas: Typically used with an Argon-CO2 mix (often 75% Argon and 25% CO2) to protect the weld area from contamination.
• Welding Parameters: Adjust voltage, amperage, and wire feed speed according to the thickness of the material and the welding position to optimize performance.
• Surface Preparation: While it can handle some surface contamination, cleaner surfaces result in higher quality welds.

Overall, E70s-2 is a reliable and versatile welding wire, favored for its strong mechanical properties and adaptability to various welding conditions.

Characteristics of E6010 Electrodes

 E6010 is a widely used electrode for Shielded Metal Arc Welding (SMAW) known for its deep penetration and ability to handle dirty, rusty, or painted surfaces. Here are the detailed characteristics, applications, and guidelines for using E6010 electrodes:

Characteristics of E6010 Electrodes

1. Composition and Coating : E6010 electrodes have a cellulose-sodium coating which produces a forceful, deep penetrating arc.

2. Current Type: Designed for Direct Current Electrode Positive (DCEP), also known as reverse polarity.

3.Penetration: Offers deep penetration, making it suitable for welding through surface contaminants.

4. Arc Characteristics: Provides a fast-freezing slag that helps in vertical and overhead welding.

5. Mechanical Properties: The tensile strength of the weld metal is typically 60,000 psi.

Applications of E6010 Electrodes

Root Pass Welding: Commonly used for the root pass in pipe welding, especially in the pipeline and oil industries.

Structural Welding: Suitable for construction where strong welds are required, and the surfaces may not be clean.

Repair Work: Ideal for maintenance and repair welding where the base material might be coated with rust or paint.

Field Erection and Fabrication: Useful in outdoor environments where conditions may not be ideal.

 Welding Positions

E6010 electrodes are versatile and can be used in all positions:

Flat

Horizontal

Vertical Up

Overhead

Technique and Guidelines

1. Preparation: Minimal surface preparation is required, but removing excessive rust or paint can improve results.

2. Current Setting: Generally used with DCEP at higher current settings to achieve deep penetration. Typical amperage ranges are:

 1/8 inch (3.2 mm)  rod: 75-130 amps

 5/32 inch (4.0 mm) rod: 110-165 amps

 3/16 inch (4.8 mm) rod: 140-210 amps

3. Arc Length: Maintain a short arc length to ensure stable arc and proper penetration.

4. Travel Speed: Use a steady travel speed. Too fast can lead to insufficient penetration, while too slow can cause excessive spatter.

5. Electrode Angle: For vertical up welding, maintain a slight upward angle (5-15 degrees) to control the molten pool.

 Advantages and Limitations

Advantages:

- Excellent penetration capabilities.

- Effective on contaminated surfaces.

- Versatile for various positions and conditions.

Limitations:

- Can be challenging for beginners due to the need for precise control.

- Produces significant spatter and a rough weld bead.

- Requires careful slag removal between passes.

 Example Welding Procedure with E6010

Objective: Welding a root pass on a carbon steel pipe.

1. Preparation: Clean the joint area to remove loose rust or paint. Ensure a proper fit-up of the joint.

2. Setup: Set the welding machine to DCEP and adjust the amperage based on the electrode diameter.

3. Welding:

   - Strike the arc and establish a stable bead.

   - Use a whipping or circular motion to control the molten pool and achieve proper fusion.

   - Maintain a short arc length and consistent travel speed.

   - Clean the slag between passes to avoid inclusions.

By following these guidelines, you can effectively use E6010 electrodes to achieve strong, reliable welds in various applications and positions.

Selecting the appropriate welding rod for an arc welding

 Selecting the appropriate welding rod for an arc welding procedure involves considering various factors such as the base material, welding position, joint design, and desired mechanical properties of the weld. Here are the key steps and considerations for selecting the right welding rod:

1. Identify the Base Material

The type of metal you are welding is crucial in selecting the appropriate welding rod. Common base materials include:

• Carbon Steel
• Stainless Steel
• Aluminum
• Cast Iron
• Nickel Alloys

2. Determine the Welding Process

Different welding processes may require different types of rods:

• Shielded Metal Arc Welding (SMAW): Uses consumable electrodes (welding rods) coated with flux.
• Gas Metal Arc Welding (GMAW/MIG): Uses a continuous solid wire electrode.
• Flux-Cored Arc Welding (FCAW): Uses a continuous tubular wire filled with flux.

3. Choose the Electrode Type and Size

For SMAW, commonly used electrodes include:

• E6010: Deep penetration, good for dirty or rusty steel.
• E6011: Similar to E6010 but can be used with AC current.
• E6013: Smooth arc, good for thin materials and general-purpose welding.
• E7018: Low-hydrogen rod, provides strong welds with good crack resistance, suitable for structural steel.

The electrode size affects the weld penetration and the amount of filler metal deposited:

• 1/16 inch (1.6 mm)
• 5/64 inch (2.0 mm)
• 3/32 inch (2.4 mm)
• 1/8 inch (3.2 mm)
• 5/32 inch (4.0 mm)

4. Consider the Welding Position

Different electrodes perform better in different positions:

• Flat and Horizontal Positions: E7018, E7024
• Vertical and Overhead Positions: E6010, E6011

5. Assess the Joint Design and Thickness

• Thin Materials: Smaller diameter rods like E6013.
• Thicker Materials: Larger diameter rods like E7018.
• Joint Types: For example, a butt joint might require different penetration characteristics compared to a fillet joint.

6. Desired Mechanical Properties

The mechanical properties of the weld metal should match or exceed those of the base material:

• Tensile Strength
• Ductility
• Impact Resistance
• Corrosion Resistance (for specific applications)

7. Other Considerations

• Power Source Compatibility: Ensure the rod matches your welding machine’s capabilities (AC or DC).
• Skill Level: Some rods are easier to use and better suited for beginners (e.g., E6013).

Example Selection Process

Welding Carbon Steel with SMAW in Vertical Position

1. Base Material: Carbon Steel
2. Welding Process: SMAW
3. Electrode Type: E6010 or E6011 for good penetration and ease of use in vertical positions.
4. Electrode Size: 3/32 inch (2.4 mm) or 1/8 inch (3.2 mm), depending on the thickness of the material.
5. Welding Position: Vertical, so E6010 or E6011 is appropriate.
6. Mechanical Properties: E6010 and E6011 provide sufficient tensile strength for general carbon steel applications.

By following these steps and considering each factor, you can select the most suitable welding rod for your specific arc welding procedure.

Butt welding Joint configuration

ROOT OPENING : 

 The distance between the two pieces at the root of the weld (or) A seperation at the joint root between two work pieces 

ROOT FACE  : 

The distance from the root of the joint to the point where the bevel angle begins or The portion of the groove space adjacent to the joint root. 

Common interview questions for a structural fabrication

common interview questions for a structural fabrication:

1.Can you describe your experience with structural fabrication?

2.What types of materials are you most experienced with in structural fabrication?

3.How do you ensure accuracy and precision in your fabrication work?

4.Can you explain your process for interpreting technical drawings and blueprints?

5.Have you ever encountered challenges in a fabrication project? How did you overcome them?

6.What safety measures do you prioritize in a fabrication environment?

7.Can you discuss any experience you have with welding techniques relevant to structural fabrication?

8.How do you stay updated on advancements and best practices in structural fabrication?

9.Can you provide examples of projects where you demonstrated innovation or problem-solving skills in fabrication?

10.How do you approach quality control and inspection in structural fabrication work?

11.Can you discuss your experience working with different tools and equipment used in structural fabrication?

12.Have you ever worked on a team for a fabrication project? How do you contribute to team success?

13.What motivates you in a fabrication role, and why are you passionate about this field?

14.How do you prioritize tasks and manage your time effectively in a fast-paced fabrication environment?

15.Can you describe a time when you had to adapt to changes or unexpected challenges in a fabrication project?

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