How to Weld Hardox 400, 450 and 700?

What is Hardox 400 material?

Hardox 400 is abrasion-resistant steel material created by SAAB company having a hardness value of of 400 HBW or 589 HV or 54 HRC level. The hardox material provide high hardness for abrasion resistance, have good toughness, ductility and weldability.

Material Specification

EN 10029, EN 10051

Chemical and mechanical properties

Chemical and mechanical properties of Hardox 400 material are given in below Table.

Carbon Equivalent for Hardox 400 Steel

The CE Value of Hardox 400 is typically depend on material thickness. The CE value increase with increase in plate thickness. The hardox CE value can be 0.41 to 0.92 as given in below table.

Welding Electrode for Hardox 400

SMAW or stick Welding of Hardox 400 can be done using E7018 or E8018 type electrode. TIG and MIG welding of Hardox shall be done using ER70S-6 or ER80S-G type consumables. These low alloy or carbon steel consumable have low hardness thus good to weld hardox to avoid hydrogen cracking during welding. The final layer or also called capping layers need to be deposited using hard metal metal (Hard facing) which need to be having similar hardness to Hardox material. Usually, Hard facing is one on the top surfaces for this purpose.

Below table give the summary of welding consumable for Hardox welding.

Hard Facing consumables for Hardox material

Different type of consumables can be used for hard facing on Hardox material such as Iron base, Nickel and Cobalt base, and copper base. A summary of mostly used Nickel and cobalt base consumables are given in below table. More details about these consumables can be found in ASME Section IIC, SFA 5.13.

Before depositing the hard facing weld metal, it is advised to weld a buffer layer of E307 or E309L (SFA 5.4) with SMAW or stick welding. TIG or MIG welding buffer layer can be deposited using ER307 or ER309L according to SFA 5.9 as shown in below figure.

Selection of electrode for hard facing is based on the hardness value required for the weld deposit.

Typical hardness values for multilayer welds made using cobalt base electrodes are:
1. ECoCr-A 23–47 HRC
2. ECoCr-B 34–47 HRC
3. ECoCr-C 43–58 HRC
4. ECoCr-E 20–32 HRC
Hardness values for single layer deposits will be lower because of dilution from the base metal.

Preheat and interpass temperature for Hardox welding

Preheat and interpass temperature control is very important for Hardox welding. Due to their high carbon equivalent, they are very prone to weld cracking. so high preheat is usually required. Preheat temperature for Hardox material is given in below table in inches-Fahrenheit. The temperature is dependent on material thickness. Higher the thickness, higher the preheat temperature.

The below table gives the temperature in mm-Celsius.

Post-Heating of Hardox material

Post heating of hardox 400, 500 or other materials is not required and also not recommended. As PWHT can change the mechanical properties of the base material.

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