Applied Welding Engineering

Processes, Codes, and Standards

Ramesh Singh

• Publisher: Butterworth-Heinemann
• Year: 2020
• ISBN:
  9780128223994
• Edition: 3
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

Applied Welding Engineering: Processes, Codes and Standards, Third Edition, provides expert advice on how to comply with international codes and work them into "day-to-day" design, construction and inspection. This new edition covers advances in automation and robotic welding in advanced manufacturing, the applications of friction stir welding, and standards and codes. The science of metallurgy, including Alloys, Physical Metallurgy, Structure of Materials, Non-Ferrous Materials, Mechanical Properties and Testing of Metals and Heal Treatment of Steels is also considered, as are Welding Metallurgy, Welding Processes, Nondestructive Testing and Codes and Standards. Case studies bridge the gap between theory and the world of welding engineering.

Other topics cover Mechanical Properties and Testing of Metals, Heat Treatment of Steels, Effect of Heat on Material During Welding, Stresses, Shrinkage and Distortion in Welding, Welding, Corrosion Resistant Alloys-Stainless Steel, Welding Defects and Inspection, Codes, Specifications and Standards.

• Includes the very latest on automation and robotic welding in advanced manufacturing environments
• Explains how to weld a range of common metals, also including technical instructions
• Provides coverage of international codes and standards relevant to welding
• Addresses a wide range of practical welding themes, including stresses and distortion, corrosion, weld defects and nondestructive testing

Section 1

Introduction to Basic Metallurgy

1

Introduction

Abstract

This chapter is an introduction to metallurgy, with definitions and explanations of a few very commonly used terms related to material extraction and processing.

Keywords

Process metallurgy; Physical metallurgy; Mechanical metallurgy; Iron; Smelting

When we talk of metallurgy as a science of the study of metals, the first question that arises in the mind is “What is a metal?” Most of us can recall the introductory study of metals in basic physics in school.

Metals are best described by their properties. Metals are crystalline in the solid state. Except for mercury, metals are solid at room temperature; mercury is a metal but in liquid form at room temperature. Metals are good conductors of heat and electricity, and they usually have comparatively high density. Most metals are ductile, a property that allows them to be shaped and changed permanently without breaking by the application of relatively high forces. Metals are elements, and metal are also alloys created by man in pursuit of specific properties. Aluminum, iron, copper, gold, and silver are examples of metals as elements, and brass, steel, bronze, etc. are examples of alloys, the man-made metals.

Metallurgy is the science and technology of metals and alloys. The study of metallurgy can be divided into three general groups:

1. 1. Process metallurgy
   Process metallurgy is concerned with the extraction of metals from their ores and the refining of metals. A brief discussion on production of steel, castings, and aluminum is included in this section.
2. 2. Physical metallurgy
   Physical metallurgy is concerned with the physical and mechanical properties of metals affected by composition processing and environmental conditions. A number of chapters in this section specifically address this topic.
3. 3. Mechanical metallurgy
   Mechanical metallurgy is concerned with the response of metals to applied forces. This is addressed in subsequent chapters of this section.

Pure metals and alloys

Pure metals are soft, weak, and used only for specialty purposes such as laboratory research work and electroplating. Foreign elements (metallic or nonmetallic) that are always present in any metal may have beneficial, detrimental, or no influence on a particular property. Whereas disadvantageous foreign elements are called impurities, advantageous foreign elements are called alloying elements. When alloying elements are deliberately added, the resulting metal is called an alloy. Alloys are grouped and identified by their primary element metal, e.g., aluminum alloy, iron alloy, copper alloy, nickel alloy, and so on.

Most of the metals as elements are not found in nature in their usable form. They are generally found in their various oxide forms called ores. The metals are recovered from these ores by thermal and chemical reactions. We shall briefly discuss some of these processes. The most common and abundantly used metal is iron, and its recovery from nature by various means is discussed in the following paragraphs.

Smelting

Smelting is an energy intensive process used to refine an ore into a usable metal. Most ore deposits contain metals in a reacted or combined form, such as magnetite (Fe₃O₄), hematite (Fe₂O₃), goethite (αFeO(OH)), limonite (generic formula for limonite is FeO(OH)·nH₂O), and siderite (FeCO₃), which are iron ores, and Cu₅FeSO₄, which is a copper ore. The smelting process melts the ore, usually for a chemical change to separate the metal, thereby reducing or refining it. The smelting process requires a lot of energy to extract the metal from the other elements.

There are other methods of extraction of pure metals from their ore. Some of these use an application of heat, leaching in a strong acidic or alkaline solution, or by electrolytic processes.

Iron

The modern production processes for recovery of iron from ore includes blast furnaces to produce pig iron, which contains carbon, silicon, manganese, sulfur, and phosphorous, and many other elements and impurities. Unlike wrought iron, pig iron is hard, brittle, and cannot be hammered into a desired shape. Pig iron is the basis of a majority of steel production. A majority of steel produced in the world is created through pig iron production.

Sponge iron

Removing oxygen from the ore by a natural process produces a relatively small percentage of steels in the world. This process uses less energy and is a natural chemical reaction method. The process involves heating the naturally occurring iron oxide in the presence of carbon, which produces “sponge iron.” In this process, the oxygen is removed without melting the ore.

Iron oxide ores extracted from the Earth are allowed to absorb carbon by a reduction process. In this natural reduction reaction, as the iron ore is heated with carbon, it results in a pop-marked surface, hence the name “sponge iron.” The commercial process is a solid solution reduction, also called direct-reduced iron (DRI). In this process, the iron ore lumps, pellets, or fines are heated in a furnace at 800–1500°C (1470–2730°F) in a carburizing environment. A reducing gas produced by natural gas or coal, and a mixture of hydrogen and carbon monoxide gas, provides the carburizing environment.

The resulting sponge iron is hammered into shapes to produce wrought iron. The conventional integrated steel plants of less than one million tons annual capacity are generally not economically viable, but some of the smaller capacity steel plants use sponge iron as a charge to convert iron into steel. Because the reduction process of sponge iron is not energy intensive, the steel mills find it a more environmentally acceptable process. The process also tends to reduce the cost of steelmaking. The negative aspect of the process is that it is slow and does not support large-scale steel production.

Iron alloys that contain 0.1% and 2% carbon are designated as steels. Iron alloys with greater than 2% carbon are called cast irons.

2

Alloys

Abstra...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• Preface to the first edition
• Preface to the second edition
• Preface to the third edition
• Acknowledgments
• Section 1: Introduction to Basic Metallurgy
• Section 2: Welding Metallurgy and Welding Processes
• Section 3: Nondestructive Testing
• Section 4: Codes and Standards
• Index