In order to effectively weld, you need to have a thorough understanding of various metals and their properties. Whether it’s preheating, interpass temperature, or determining whether a material needs a slow cooling rate. It’s critical that you understand the ideal temperature for each stage of your welding project. In this blog, you’ll learn why thermometers are important for effective welding. You’ll also compare and contrast the impact both contact or infrared thermometers have on a professional and effective weld.

Why You Need a Thermometer

Different metals require different temperatures for effective welding. Whether it is preheat or a need to monitor the maximum interpass temperature, it’s always important to check your work.

Preheating is one of the most important steps to many welding projects. Without proper preheating, many alloys have the potential to crack or harden. The expansion and contraction due to intense heat can cause abnormal stress on the project. In order to monitor preheat temperature, you need a reliable and convenient thermometer.

There are three main factors that typically call for preheating. Every welding application is unique, so consider your own situation carefully. You may need to preheat the material if you’re working with:

  • Weld joints that are highly restrained
  • Thicker materials susceptible to hydrogen-assisted cold cracking
  • Materials with a high carbon equivalent

If any of these apply to your project, consider using one of these ways to preheat. Most projects can easily reach appropriate temperatures with a heating torch. Larger projects however or those requiring higher preheat temperatures may require heating pads or coils.

In order to accurately assess the preheat most welders choose either a contact or infrared thermometer. Here are some of the advantages and disadvantages of both types for use with preheating.

Advantages of Contact Thermometers

The most popular thermometer is a contact thermometer. The contact device is very easy to use. Once you believe you have reached the preheat temperature, hold the thermometer against the metal. It will display the actual surface temperature after a short period of contact.

There is a wide range of contact thermometers available to welders. These typically provide an accurate temperature reading within a single degree and have a long-lasting battery.

Disadvantages of Contact Thermometers

Digital contact thermometers rely on batteries to operate. This can be frustrating if batteries run out during operation. Contact thermometers are also much more expensive than most infrared options. Because contact with the surface is required this generally requires the welder to cease preheating operations to check the temperature intermittently.

The type of contact thermometer being used also determines the reaction time of the temperature display. Some high tech thermometers display temperature within seconds while others take time to stabilise to the actual temperature.

Advantages of Infrared Thermometers

Non-contact thermometers, also known as infrared (IR) thermometers, obtain a temperature measurement from a distance. Fast, simple and affordable, an infrared welding thermometer is a great way to get hassle-free temperature readings.

An infrared thermometer offers unparalleled ease of use. Simply point and pull the trigger. You’ll be able to get a quick reading without making contact with any surface. The reading will be clear and easy to read. In fact, you can often get a reading from several feet away from the material.

Disadvantages of Infrared Thermometers

Infrared thermometers have one major disadvantage. This is that they do not generate accurate readings when being used on shiny or reflective surfaces.

The operator is also required to understand the relationship between distance to spot ratio. Distance to spot (D:S) is the diameter of the area being measured compared to the distance from the target. Measuring from distances not suitable to the specific type of thermometer you’re using can result in inaccurate readings. Be sure to check the instructions of each specific infrared thermometer.

Discover the Best Thermometer and Preheating Techniques

Whether you’re searching for tips and tricks for preheating alloys or need professional welding procedures or training, contact Technoweld. Our courses and expert inspectors are some of the most confident and effective in Australia. You’ll be able complete expert inspections or learn more about how thermometers can help you throughout the welding process.