Table of Contents
What is Preheat Temperature in Welding?
Importance of Preheating
Recommended Preheat Temperatures for Common Metals
Methods to Determine Preheat Temperature
What is Interpass Temperature in Welding?
Importance of Interpass Temperature
Final Note: Striking the Right Balance
Key Takeaways
In welding, both preheating and interpass temperature are critical parameters that significantly influence weld quality, mechanical strength, and overall structural performance. These practices are implemented before welding (preheat) and between welding passes (interpass) to control the material's heating and cooling rates.
Understanding and maintaining the correct preheat temperature for welding helps prevent cold cracking, improve arc stability, and reduce moisture-related defects. Similarly, regulating the interpass temperature in welding between passes ensures consistent metallurgical properties and prevents overheating, especially during multi-pass welds. By understanding these thermal practices, welders can avoid common welding issues such as distortion, hydrogen-induced cracking, and loss of toughness.
Preheating refers to the process of increasing the temperature of the base or parent material on both sides of the joint. The temperature in welding should be higher than the ambient temperature. In simple terms, preheat temperature is the minimum temperature required by the base metal before welding begins.
The purpose is to create optimal thermal conditions that allow controlled heat flow and reduce temperature differentials during welding, especially for thick or high-strength steels.
The preheat temperature for welding is necessary for the following reasons:
Decrease shrinkage stresses in the weld and Heat Affected Zone (HAZ).
Improve the microstructure of HAZ.
Slow down the cooling rate to reduce hardness.
Remove moisture to prevent hydrogen buildup, porosity, and the likelihood of cracking.
Reduce distortion that might occur due to thermal stresses.
Compensate for high heat loss.
Eliminate grease, oil and scale for the joints to enable quick welding speeds.
These benefits collectively contribute to a more reliable, defect-resistant, and higher-strength weld, especially in critical structural applications.
The required preheat temperature depends on several material and process factors. Below are general guidelines:
Steel: 30-50°C above the upper transformation temperature
Cast Iron: Approximately 200–310°C
Carbon Steel: Variable based on:
Chemistry of the base metal
Strength of the base metal
Thickness of the base metal
Use of the low-hydrogen process
Joint type, thickness and restraint
To ensure accuracy, welders can rely on a number of trusted methods to determine preheat temperature:
HAZ Hardness Control Method
Manufacturer’s Recommendations
Hydrogen Control Method
Slide Rule Preheat Calculator
Table 3.3 in the American Welding Society’s D1.1 Structural Welding Code
Interpass temperature refers to the base material’s temperature before the next pass is laid. It is measured in the region between two beads or layers and must remain within a defined temperature range throughout multi-pass welds.
The interpass temperature in this context refers to the controlled temperature maintained between successive weld passes. It is typically specified as a minimum and maximum temperature range.
Note: It is indicated in terms of minimum and maximum temperatures. The minimum interpass temperature should be at least as high as the maximum one.
Maintaining correct interpass temperature in welding is critical for ensuring weld quality, especially in high-strength and alloy steels. Key benefits include:
Avoid overheating.
Control the microstructural development of weld metal.
Ensure the consistency in all welds made in the procedural qualification.
Reduce the loss of alloying elements in welds.
Improve the notch toughness properties.
Prevent deterioration of mechanical properties of weld metal and HAZ.
Lower the probability of distortion.
Minimize the risk of hydrogen, solidification and liquid cracking.
Maintain sufficient wetting of the molten pool onto the base material.
Both preheat and interpass temperatures directly influence the cooling rate of the weld. From preventing cracking to enhancing weld toughness, these parameters help ensure durable and defect-free welds.
Looking to optimise your welding process with expert-grade consumables?
At D&H Sécheron, we offer a full range of advanced welding products engineered to meet the most demanding structural and industrial requirements.
Explore our welding consumables or consult our experts for tailored recommendations that support your application.
Preheat temperature prepares the base metal prepares it for controlled welding and reduces the risk of cracks.
The preheat temperature for welding varies with the material chemistry, thickness, and process type.
Tools like AWS D1.1 and hydrogen control methods help define optimal preheat values.
Interpass temperature ensures consistency between passes and avoids overheating.
Together, these controls enhance strength, minimise distortion, and improve weld quality.
27 July 2025 | Welding
An In-Depth Exploration of Low-Alloy Steel: Your Comprehensive Guide27 July 2025 | Welding
Nagpur - Bori - Tuljapur Road MSH-3 in Yavatmal District (Maharashtra)27 July 2025 | Welding
Guidelines to Understand Gas Welding: Applications, Advantages & Disadvantages27 July 2025 | Welding
3 Tips for Finding the Best Mild Steel Electrode for Your Application27 July 2025 | Welding
How to Select the Right Welding Filler Wires for Stainless Steel Welding?27 July 2025 | Welding
Building the Narendra Modi Stadium with Norma V and Autotherme-1 Electrodes27 July 2025 | Welding
Low Alloy Steel Welding in a (PEB) Pre Engineered Building Structure27 July 2025 | Welding
Welding Rods: Different Types and Tips for Properly Storing and Handling27 July 2025 | Welding
Tips for Flawless Welds with Stainless Steel Electrodes: Pros and Cons27 July 2025 | Welding
Exploring Applications and Benefits of Stainless Steel Welding Electrodes27 July 2025 | Welding
Welding Basics: Joining Metals with Heat and Pressure - A Beginners Guide27 July 2025 | Welding
Forehand vs. Backhand Welding Techniques: Choosing the Right Method27 July 2025 | Welding
Welding Innovations to Improve Manufacturing Productivity & Quality27 July 2025 | Welding
Distinguishing Low-Alloy Steel from High-Alloy Steel: Understanding the Variations27 July 2025 | Welding
Hard Facing Wire - Understanding the Process and Achieving Optimal Result27 July 2025 | Welding
Exploring the Advantages of Stainless Steel Electrodes in Welding Applications27 July 2025 | Welding
Weathering Steel vs. Traditional Steel: A Comparative Analysis of Performance27 July 2025 | Welding
Choosing the Right Welding Rod: Why 6013 Electrodes Might Be Your Ideal Option27 July 2025 | Welding
Why 7018 Electrodes Are Preferred for High-Strength Welds in Pipeline Construction27 July 2025 | Welding
Understanding Weathering Steel: Characteristics, Advantages, and Common Applications27 July 2025 | Welding
Filler Wire vs. Stainless Steel Filler Wire: Understanding the Key Differences27 July 2025 | Welding
What are Mild Steel Electrodes? A Detailed Explanation of Different Types with Examples27 July 2025 | Welding
Exploring the Impact of Filler Material on Welding Quality and Durability27 July 2025 | Welding
Choosing the Right Cast Iron Electrode for Different Welding Projects27 July 2025 | Welding
Top Advantages of Cast Iron Electrodes for Industrial Welding Applications27 July 2025 | Welding
Key Benefits and Challenges of Using TIG Welding in Industrial Projects27 July 2025 | Welding
Lotherme-601: A Game-Changer for Restoring Shoulder Pins in Heavy Machinery27 July 2025 | Welding
How D&H Sécheron Helped Repair a Rotary Kiln’s Cooler Section with LoTherme 35227 July 2025 | Welding
Piston Repair for Mining Industry: Cost-Effective Solutions with LoTherme 46827 July 2025 | Welding
Top 5 Advantages of Flux Cored Arc Welding for Heavy-Duty Applications27 July 2025 | Welding
5 Reasons Why 7018 Electrode is the Gold Standard for Welding Professionals27 July 2025 | Welding
Revitalising Power Plant Efficiency: The Role of LoTherme 470M in Drive Shaft Repairs