Materialval och materialegenskaper

• Text is about materials science, covering topics from material selection to environmental impact

Selecting Materials

• An example is provided about selecting the best materials for parts of an ironing board
• Considerations include heat resistance, friction, bending and moisture resistance
• The material for the board should not stain, let moisture through, or reflect heat
• The frame needs to have a stable and lightweight construction and resistant to rust
• Material should be affordable to keep the product competitive
• Achieving these manufacturing goals requires understanding material properties and processing

Material Properties

• Material properties are critical for material selection and broadly categorized as physical, chemical, and mechanical
• Physical properties include density, thermal expansion, heat conductivity, and resistivity
• Chemical properties include solubility and reactivity with other substances
• Mechanical properties include tensile strength, compressive strength, impact strength, torsion, fatigue strength, and how the material deforms under stress

Material Structure

• Material properties depend on material structure
• All materials are composed of atoms
• An element consists of only 1 type of atom
• Different atoms can combine to form chemical compounds, where atoms are held together by molecules
• Substances made of atoms or molecules are connected in different ways
• Metals have a crystalline structure, where atoms are arranged in a 3D pattern called a lattice
• Atoms are held together by an "electron cloud," which makes metals good electrical conductors
• These atomic lattices are large and form crystals/grains containing 10^15 - 10^25 atoms; the crystals give the metal it's properties
• Grains in a metallic microscope are often oriented differently and refract light differently, revealing grain boundaries
• Other materials such as wood and plastic are made of molecules held by electron pair bonds and/or ionic bonds
• In construction materials, atoms bond into long molecules - for example, with a mass of 1.6 x 10^-15 mg
• Wood has naturally structured long molecules, while plastic is created through polymerization of shorter molecules

Material Standards

• Material standards are important so parts fit, even if manufactured in different countries
• Standards ensure consistent quality, readability, and compliance and help businesses guarantee work is done correctly
• Standards are used in diverse fields, including metals, electrical components, drawings, testing, chemicals, measurement, and manufacturing
• The Swedish Standards Institute (SIS) standardizes products/services in Sweden
• SIS's role is to represent standardization nationally and internationally
• SIS Forum AB provides training and consultation, and SIS publishes standards
• Approximately 1500 new national, European (CEN), and global (ISO) standards are developed annually

Standard Organizations

• Various committees propose standards
• Proposals are further processed by European/International committees
• The European Committee for Standardization (CEN) manages all standards, except for electrical and telecommunications
• The European Committee for Electrotechnical Standardization (CENE-LEC) handles electrical standards
• The European Telecommunications Standards Institute (ETSI) handles telecommunication standards

Global Standard Organizations

• The International Organization for Standardization (ISO) handles all standards except electrical and telecommunications
• The International Electrotechnical Commission (IEC) handles electrical standards
• The International Telecommunications Union (ITU) handles standards related to telecommunications

Standard Classification

• Different texts discuss standardization
• Standards are divided into groups based on what they address
• Basic standards address general requirements in technology areas like terminology, measurement systems and math
• Product standards detail the properties of a product, like dimensions and strength
• Functional standards focus on a product's properties, like its purpose
• Construction standards describe dimensions and materials
• Standards for testing methods describe different methods for testing materials and products
• Standards for management systems deal with organizations, quality control, and environmental considerations

Swedish Standards

• Sweden previously used a numerical system with three groups of numbers to categorize standards
• SS stands for Swedish Standard
• The first two numbers relate to a specific area (ex: SS 14 for metallic material)
• Later numbers indicate material type and properties (SS 1415 xx = unalloyed steel)
• New standards are now coordinated with EU/ISO and will be marked with SS-EN or SS-ISO

European standards

• The EU tries to standardize products
• The goal of standardization is to see details of a material by looking at the product name
• The first part of the European Standard name (like SS-EN) varies by country
• The rest of the name remains consistent so the country code is often dropped

Standard Systems for Steel

• Steel follows an alphanumeric and a numerical standard
• These standards are SS-EN 10027-1 and SS-EN 10027-2
• SS-EN 10 027-1 classifies steel by application and properties (group 1) and chemical composition (group 2)

SS-EN 10 027-1 Classification system

• Group 1 uses a letter for steel type and numbers for properties (S355 J2 C), in the example, steel and yield strength, charpy test and forming
• Group 2 categorizes by alloy content using a chart
• Steel is designated as Unalloyed with manganese under 1%
• This excludes automatic steel, Alloyed with manganese up to 1% (including automatic steel)
• In this steel, no alloying element exceeds 5%
• Alloyed steel has at least one alloying element exceeding 5%

Other Standardization

• Other metals use similar standardization methods
• Aluminum has both numerical and chemical composition-based standards
• Numerical systems are the main approach, with chemical details as extra info

Markings

• CE marking shows an item follows standards and directives for safety
• Different levels of certification are possible, with or without the involvement of accredited 3rd parties
• ISO 9000 builds a leadership system by controlling all of an organization's functions (production, work)
• ISO 14000 is a series of standards for environmental management systems, including eco-management and audit schemes

Standard Certifications

• Certification (inspection) must be done by accredited companies
• Swedac (the Swedish Board for Technical Accreditation) handles this in Sweden

Material Testing

• Material testing is essential because construction materials can fail
• Examples of this failing can be seen with wing supports for planes, springs and bogies in train wagons
• Material testing seeks to be a complex process
• Complete material tests can be destructive (where the material is tested until broken) or non-destructive (ex: using radiography or ultrasound)

Destructive testing

• Destructive testing can not be used for materials after the material has been tested
• It uses a specific set of processes

Tensile Testing

• Testing for how much tension a material withstands
• The same amount of material used in a project is strained, measuring the point at which it breaks
• Stress values are measured in N/mm^2 and length increases are measured in mm
• Special rods are created for material tests and attached to a machine so it can measure strength
• The tool registers stress, length, and a writing implement graphs the data

Diagram Analysis

• The initial curve on a stress/strain diagram is elastic deformation, and the material returns if the stress is below the yield strength
• Plastic deformation is when the material does not return to its original shape
• The crystal structure is altered so that the material will likely fail
• Materials that will undergo use must remain in that elastic area

Hardness Testing

• Hardness testing involves pressing a hard ball/cone into the material and measuring the size of the impression
• This primarily tests the surface of a layer
• Common methods are Brinell, Vickers, and Rockwell testing
• It does not work on elastic materials like rubber, so you measure how far the test object falls

Hardness Measurement types and applications

• Brinell tests soft materials with steel balls measuring diameter and area of impression based on force
• Vickers tests hard and soft or thin objects and measures the diagonals of an impression on the object
• Rockwell provides additional options and uses a ball or diamond-shaped indentor

Impact Testing

• Some materials react differently when struck, tested using impact testing
• Impact testing uses a pendulum to strike a notched sample while measuring the energy required to break it

Impact Measurement

• Impact tests are performed by securing a test object and hitting with a weighted pendulum
• Energy absorption is measured, which relates to it's strength
• The impact resistance depends on temperature, making it essential to use low temperatures

Impact transition temperature

• Due to cooling, impact transition temperature may change
• Lower temperatures cause this reaction
• This testing is an important consideration when manufacturing components

Fatigue Testing

• Materials can break even if the math is correct and the design isn't always still
• Bridges and axles, for example, go through consistent rotation, so they need to be tested
• To find material characteristics in relation to fatigue, you can use a rotating test bar
• The bar is loaded down until the test finds that the sample falls apart
• Data is then graphed using a Wohler diagram

Non-Destructive Testing

• Involves techniques that preserve usability, such as ultrasound and radiography
• Ultrasound uses sound waves between 0.5-10MHz to locate internal cracks, recording signals on an oscilloscope
• Radiography projects radiation through a object, and a film on the far side detects cracks.
• Surface defects with magnetic materials can be found with magnetization and iron powder in oil

Liquid Penetration Testing

• A liquid with low viscosity is placed on non-magnetic materials, and the residue is wiped off after
• After it dries, the cracks can be seen through the residue

Iron and Steel

• Steel, an iron alloy with up to 2% carbon, is the most common metal used in construction
• Iron with >2% carbon is cast iron
• Alloy steels contain other metals like silicon, managanese, chromium, nickel, molybdenum and lead to enhance properties
• The most abundant iron ores are magnetite (Fe3O4) and hematite (Fe2O3); steel products are formed in two steps
• Iron ore is reduced using carbon, traditionally through a blast furnace, where sinter, carbon, and slag are added
• As the slag cools, the molten iron is separated and tapped for future oxidation in other processes to reduce carbon

Specialized Steel Production

• Iron sponge melts in various ovens and reduces oxide
• The product is unstable
• Corex-processes offer an alternative route to produce molten raw metal
• The processes include the usage of natural gas, carbon and oxygen

Steel Furnaces

• Converters tilt to add molten iron with oxygen or a mix with argon
• The Martin process used a chamber to refine additional metals

Steel Refinement

• Electric arc furnaces can make steel under vacuum conditions
• The steel can then be cast under carefully controlled conditions, where gas bubbles and non-homogenous materials can form

Material Properties

• Metallic lattices vary with the amount of carbon
• Properties of a material depend on various dimensions
• Alpha Iron, also known as Ferrite, exists below 910 degrees celcius and has a solution of about .05% carbon and can be easily resolved
• Gamma Iron, also known as Austenite, exists above 720 degrees celcius and can contain 2% carbon
• Cementite or Iron Carbide contain a mix of Iron and Carbon
• Pearlite or Ferrite is a derivative and contains different amounts of these products given carbon properties

Descriptive graph

• A diagram charts the content of these phases, including carbon
• Chemical composition is easier with high carbon
• Steel exists as alloy or nonalloy
• Those materials, alongside cast-iron can be used in the construction of other materials due to the use of alloys

Standard Steel

• Generic Structural Steel alloys generally involve a low quantity of carbon, making them suitable for buildings, bridges, lifts etc.
• Processing includes sheet metal, rods, forging and construction
• Machine Steel processes primarily involve machining with a medium level of carbon
• Spring, Screw or more secure designs are able to withstand larger products
• Hard Scaffolding involves both Alloy and Non-Alloy solutions, which are useful for small pieces or screws

Special steel properties

• Sätthärdningsstål is low-carbon for surface hardening, making it more durable
• Automatic steel consists of low carbon for machining
• Spring Steel is the most appropriate choice for high load, high flexibility and good returning of various materials
• Kallvalsad Tunnplåt often consists of a thin form factor for car bodies and certain uses

Heat Treatment

• Heat treatment changes steel by heating, holding, and cooling the material to alter it's characteristics
• Heat treatments can be used for hardening and resilience
• Different processes may affect carbon strength and heat/cooling levels

Annealing

• Annealing can be used for wire work where steel is heavily strained
• This means heating components to 500C-600C to allow the steel to normalize
• Recrystallization Annealing helps with structure
• A process heats up and normalizes the material, allowing materials to be thoroughly tempered

Steel processing

• Soft Annealing assists hard to manufacture levels, and the processing heats and cools the metal
• Normalizing is used in Steel and Forging, so heating the object returns it to normal size.
• Steel is normally heated between 750C-1050C, and then the air is allowed to freely circulate

Hardening Steel

• Hardening can be beneficial to many areas
• High carbon Steel is required and heated to harden
• This does not convert to cementite
• Martensite results from a higher volume of carbon and fast cooling around air
• The surface area is typically the most hardened area

Temper

• The hardening of the metal should cause less brittleness and heat the material upwards of a certain amount.
• A hardening treatment is done similarly to surface hardening
• Steel is heated in high carbon areas like Ammonia to a high temperate

Nitriding

• The process is very effective on small parts