AWS C3.6M:2016 pdf download.Specification for Furnace Brazing
4.1 Method of Clasification. Furnace brazed joints are classified in this specification based on two criteria: the design requirements and the consequences of their failure. It is the responsibility of the Organization Having Quality Responsibility to evaluate these or other factors and assign the proper classification. This classification controls which inspection methods and limits are required.
4.2 Class A Joints. Class A is typically chosen for joints subjected to high stresses, cyclic stresses, or both, the failure of which could result in significant risk to persons or property, or significant operational failure.
4.3 Class B Joints. Class B is typically chosen for joints subjected to low or moderate stresses, cyclic stresses, or both,the failure of which could result in significant risk to persons or property, or significant operational failure.
4.4 Class C Joints. Class C is typically chosen for joints subjected to low or moderate stresses, cyclic stresses, or both,the failure of which would have no risk to persons on property.
4.5 No Class Specified. When no class is specified on the engineering drawing or other applicable document approved by the Organization Having Quality Responsibility, Class A requirements shall apply. However, because of the confusion that can result, all engineering drawings referencing this specification should state the class of the brazed joint in the brazing symbol. Symbols shall be in accordance with AWS A2.4, Standard Symbols for Welding, Brazing, and Nondestructive Examination.
5.1 Process Description. Furnace brazing is a process in which assembled components, with brazing filler metal preplaced, are loaded into a furnace. The furnace is then purged with a neutral or reducing atmosphere, or evacuated of air, and assembled components are uniformly heated to a certain temperature (generally above the liquidus of the brazing filler metal, but less than the melting point of the base metals). The brazements are then cooled or quenched at an appropriate rate so as to minimize distortion and produce the required properties in the brazing filler metal and base material. This cycle is designed to produce the melting and solidification of the brazing filler metal required to join the components without melting or damaging the base metals.
5.2 Equipment
5.2.1 General Furnace Requirements. All brazing furnaces shall have automatic temperature control and recording devices in good working order capable of controlling the temperature profile of the furnace to the requirements of this specification. Furnaces shall have adequate capacity to accomplish uniform heating of the load at the rate required to prevent both unacceptable thermal distortion of the assemblies and liquation of the brazing filler metal. The furnace and associated equipment shall be properly maintained in good working order.AWS C3.6M pdf download.