Micro-jet cooling is an innovative method of forced cooling. It could be used to cooling after welding immediately. It allows to obtain welds with better properties in comparison to ordinary welding method. Favourable structure of weld metal deposit (WMD) with higher content of acicular ferrite (AF) could be obtained. These properties can be controlled by several variables (e. g. type of cooling gas, number of jets). Plastic properties are particularly important in case of impact load. This type of strength is very dangerous for the structure and for safety of users (ex. car body during car crash). This article presents the influence of the cooling gas and the number of jets on plastic properties of the weld joint for impact load. It is described by restitution coefficient and plastic strain.

Until that moment micro-jet technology was tested only for MIG welding process with argon as a shielded gas. An article presents actual information about innovate welding technology with micro-jet cooling. There are put down information about gases that could be chosen both for MIG/MAG welding and for micro-jet process. There were given information about influence of various micro-jet gases on metallographic structure of steel welds. Mechanical properties of weld was presented in terms of oxygen amount in WMD (weld metal deposit).

An article presents actual information about innovate welding technology with micro-jet cooling. There are put down information about gases that could be chosen for micro-jet process. There were given information about influence of various micro-jet gases on metallographic structure of steel welds.

Low carbon steel weld structures generally exhibit a very linear stress-strain relationship. In the study of strength of materials, the compressive strength is the capacity of a material or structure to withstand loads tending to reduce size of structure. It is mainly measured by plotting applied force against deformation in a testing machine. Compressive strength is a main key value for design of welded structures.The main goal of that paper was analysing of plastic properties of frame welds which were made with various parameters of micro-jet cooling. New technology of micro-jet welding could be regarded as a new way to improve plastic properties of welds. It allows to obtain welds with better mechanical properties in comparison to ordinary welding method. Furthermore it is possible to steering of weld structure and properties of the weld. There were given main information about influence of various micro-jet gases on metallographic and properties of structure steel welds.

The paper focuses on low alloy steel after innovate welding method with micro-jet cooling. Weld metal deposit (WMD) was carried out for welding and for MIG and MAG welding with micro-jet cooling. This method is very promising mainly due to the high amount of AF (acicular ferrite) and low amount of MAC (self-tempered martensite, retained austenite, carbide) phases in WMD. That structure corresponds with very good mechanical properties, ie. high impact toughness of welds at low temperature. Micro-jet cooling after welding can find serious application in automotive industry very soon. Until that moment only argon, helium and nitrogen were tested as micro-jet gases. In that paper first time various gas mixtures (gas mixtures Ar-CO₂) were tested for micro-jet cooling after welding.