Could that person talk about the issues related to welding common types of steel?

In the welding process, in addition to proper preparation of the area to be welded, great care must be taken during the actual welding operation as well as during the appropriate heat treatment after welding; otherwise, even with the best equipment and the most suitable welding rods, it is difficult to achieve successful welding of tool steel. Preparation of the welding area: Careful preparation of the joint is very important. The cracks should be ground away to create a slope at an angle of at least 30 degrees with the vertical direction at the joint. The width at the bottom of the interface should be at least 1 millimeter, and it must be larger than the diameter of the largest electrode used. The eroded and hot-cracked areas of the hot-work tool steel should be completely ground off. The surface around the tool welding area and the surface of the joint itself must be thoroughly ground. Before welding begins, the relevant surfaces should be inspected with a penetrant to ensure that all defects have been completely removed. Once the interface is ready, the tool should be welded immediately; otherwise, there is a risk that the surface of the interface will be contaminated by dust, dirt, or moisture. Formation of the weld zone: Appropriate multi-layer welding is used to weld first on the surface of the joint. This initial layer is initially completed using small-diameter MMA electrodes (≦3.25 mm–1/8 inch in diameter) or by TIG welding (with a maximum current of 120 A). The second layer is welded using welding rods and current of the same diameter as those for the first layer, in order to prevent a too large heat-affected zone. This assumption is based on the idea that any hard and brittle microstructure formed in the heat-affected zone of the first weld layer will be tempered by the heat generated by the second weld, thereby reducing its tendency to crack. The remaining part of the joint can be welded using angles, high current, and electrodes with a larger diameter. The last few layers should extend beyond the surface of the tool steel; even small welding areas should be welded with at least two layers. Grind off the last few layers that protrude above the surface. During welding, the arc should be short, and the layers of the weld seam should be well-defined. The welding rod should be at a 90-degree angle to the surface of the joint edge in order to reduce undercutting. Additionally, the welding electrode should form an angle of 75-80 degrees with the forward movement direction. Arc initiation should take place at the welding joint, rather than on any surface where welding is not required. Cracking is likely to start at the spark initiation point. To avoid the formation of pores, at the start of welding the sparking area must be completely melted. If welding is resumed using used MMA electrodes, the impurities in the sparking area must be removed; similarly, pores in that area should be eliminated after sparking. When welding edges and corners, using a piece of copper plate or graphite as a support for the metal in the welding area helps to save both welding rods and time. Using such a support keeps the molten pool hotter, thereby reducing the risk of porosity (a low current is required when welding edges and corners). If copper or graphite is used as a support, a 1.5 mm gap must be left between the support and the surface to be welded, as slag requires space (MMA welding). For the repair or welding of more expensive tool steels, in cases where plastic mold cavities need to be polished or textured, a good bond must exist between the welded metal and the mold. Combining defects can cause problems in subsequent sparking. Expensive surfaces can be damaged by spark pores. This tool should be placed on a copper plate, with good contact required. The copper plate needs to be preheated along with the tool. Before allowing the tool to cool down, the entire welding area should be carefully cleaned and inspected. Any defects such as arc marks and burrs should be addressed immediately. Only after the tool has cooled down can the surface of the welded area be ground to be level with the surrounding surfaces, after which the next processing step can be carried out. For molds that require polishing of lake-pattern etchings, TIG welding should be used for the final layers, so as to minimize the risk of pores or slag inclusions in the welded areas.