Junior foundry worker technology

Author: Chief Editor: Liu Jirong
Publisher:
Publish Date: 2004-02-01
Features: This book is based on the "Technical Skill Level Standards for Workers" and "Occupational Skill Appraisal Specifications" jointly issued by the former Ministry of Machine Industry and the Ministry of Labor. The main content includes: metal materials and heat treatment, mold materials, molding, core making, drying, assembly, pouring, and finishing of molds (cores); casting alloys and their melting; gating systems, risers, chills, and casting fins; casting defects, machine molding, and special casting. The book strives to meet practical needs in content writing, with strong industry relevance and a focus on practicality. It adopts the latest national standards, legal metrological units, and new terms and terminology, emphasizing the integration of theory and practice. It organically combines "professional knowledge" and "operational skills," facilitating training and skill assessment for foundry workers in various enterprises.
Excerpt:
III. Melting The process of heating metal from a solid state to a molten state is called melting. There are various types of melting equipment, such as arc furnaces, open-hearth furnaces, induction furnaces, crucible furnaces, and reverberatory furnaces. In production, the choice of melting equipment depends on the type of alloy, scale, and economic considerations.
IV. Drying of Molds (Cores) For some large or high-quality castings, dry-mold casting is generally used, meaning the molds (cores) need to be dried. The drying process is typically carried out in a drying furnace, consisting of three stages: heating, holding, and cooling.
V. Pouring The operation of pouring molten metal from a ladle into a mold is called pouring. A ladle refers to a container used for holding, handling, and pouring molten metal. Ladles are made with a steel shell and lined with refractory materials. They are divided into two types based on the alloy being poured: one for pouring iron and non-ferrous metal melts (called ladles), which include manual and electric ladles; the other for pouring steel melts (called steelmaking ladles), which are further divided into single-eye and double-eye ladles. The capacity of various ladles also varies, ranging from a few tens of kilograms to several tens of tons. In actual production, the appropriate ladle must be selected based on the type and weight of the alloy being poured, as well as the workshop's facilities.
VI. Finishing The process of removing surface scale, mold sand, excess metal, and other residues from the casting after sand removal is called finishing. The removal of casting runners and risers is often done using gas cutting or hammering, while surface finishing can be achieved using methods such as grinding wheels, tumblers, shot peening, or sandblasting.
VII. Heat Treatment of Castings The process of heating a casting to a certain temperature range, holding it for a period, and then cooling it to an appropriate temperature at a specified rate is called heat treatment. The purpose of heat treating castings is to eliminate casting stresses, prevent deformation or cracking, and improve the mechanical and machining properties of the castings. Heat treatment methods include annealing, normalizing, and tempering. The choice of heat treatment method depends on the material and technical requirements of the casting.
Section II: Common Tools and Process Equipment for Molding
I. Molding Tools
1. Shovel (also called a spade) Used for mixing mold sand and lifting it to a designated location.
2. Sieves There are two types: rectangular and circular (see Figure 1-1). The rectangular sieve is used for sieving base sand or mold sand. When in use, two people hold the handles at both ends of the sieve, lift it, and move it back and forth to sieve the sand. The circular sieve is usually a hand sieve, used for sieving facing sand onto the pattern by holding it in the hand and shaking it left and right.
3. Rammer Used for compacting mold sand during molding (see Figure 1-2). The head of the rammer is divided into flat and flat types. The flat head is used for compacting mold sand around the pattern and along the mold box edges or in narrow areas, while the flat head is used for compacting the surface of the mold.
4. Scraper (also called a straightedge) Made of flat wooden or metal plates, with a length slightly longer than the width of the mold box. After the mold sand is compacted, it is used to scrape off excess sand above the mold box.
5. Vent Pin (also called a vent needle) There are straight and bent types (see Figure 1-3).