Tham khảo tài liệu 'welding materials handbook part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | lẵlTnnnilPTưw Section 2. WEARFACING INTRODUCTION Abrasion-resistant alloys have poor impact properties. Conversely impact-resistant alloys have poor abrasion resist ante. The higher an alloy s abrasion resistance the lower its ability to withstand impact and vice-versa. Between these two extremes are numerous wearfacing alloys that combine varying degrees of resistance to abrasion with the ability to absorb a fair amount of impact. The selection of a wearfacing alloy for a certain application is determined by the requirements of its anticipated service. The Seabee Welder can greatly extend the usable life of construction equipment by selecting the appropriate alloy and applying it with the correct procedure. A regular wearfacing program extends equipment life allows it to operate more efficiently with less down time and greatly reduces the need for spare parts. The following section illustrates various parts of construction equipment and describes the correct repair welding procedures to use on them. Each diagram provides one or more electrodes that maybe used as alternates whenever the most desirable rod is not available. The numeral given is the page number where information on the recommended rod can be found. WORKPIECE PREPARATION Remove dirt oil rust grease and other contaminants before welding. If you do not you are inviting porosity and possible spalling. Prepare a sound foundation by removing fatigued rolled-over metal. Repair cracks with compatible electrodes. PREHEAT Preheating of base metal is sometimes necessary to minimize distortion to prevent spalling or cracking or to avoid thermal shock. Preheat temperature is influenced by two important factors the carbon content and alloy content of the base metal. The higher the carbon content the higher the required preheat temperature. The same is true to a slightly lesser degree for the total content of other alloys. After the surface has been brought to the required 2-1 PREHEAT Continued preheat temperature
