Metals PDF

Material does not occur in its pure form in nature, but we do find it is **Ores (malmi)** which is metal oxides (bonds with oxygen). Ores are refined from raw material into usable material. Reduce is done by adding chemical carbon and heat. Mechanical properties though depend on materials "impuritie...

Material does not occur in its pure form in nature, but we do find it is **Ores (malmi)** which is metal oxides (bonds with oxygen). Ores are refined from raw material into usable material. Reduce is done by adding chemical carbon and heat. Mechanical properties though depend on materials "impurities". Gold, silver and platinum can occur still in their pure form. **Oxidizing/corroding** Starts returning to original state of ore. **Steel** Alloys are based on iron (Fe). **Processing Ore** Cleaningbreaking/sintering -bringing to equal sizespelleting - forming powder particlessorting -- iron /non-ironbaking Ore must be reduced (removing oxygen) so the pelletized iron oxide goes into a blast furnac (uuni) from above and the liquid steel collects at the bottom. Hot air +1000 Celsius and furnac has a load consisting of iron ore, coke and limestone. Since the iron in iron ore occurs as oxide, it can be released by removing the oxygen, i.e. by reduction. The coke in the furnace provides heat and at the same time also provides the reducing gas that chemically removes oxygen atoms from the iron oxide, thus creating the desired iron. **Crude iron** Is not usable as construction materials due to reason that it's very brittle and stiff material and it contents carbon only 4-5%. Excess admixture must be removed by reducing carbon and reducing silicon and phosphorus. **Crude iron to steel** Has higher amounts of carbon© which means it has high tensile strength/hardness, low toughness, elongation(venymä), malleability, machinability and melting therefore Crude iron is hard, but very brittle and difficult to process. To process it's mandatory to remove carbon. Pure iron contains 0.005% carbon (weak/ductile) and steel is type of iron with 0.06 to 2% carbon. If iron contains more than 2% carbon, it is classified as cast iron. **Refinement process** The process starts by adding oxygen again, which initiates oxidation. The oxygen binds with carbon in the iron. As a result, the carbon content in the metal decreases. Steel scrap is mixed into molten material to improve properties and reduce costs. **Open heart furnace** A mixture of fuel and air is blown over the molten bath of iron to maintain the heat required for the refining process. **Electric arcs process** The molten bath is kept warm by electric arcs that generate intense heat during the steel making process. **Basic oxygen steel** Pure oxygen is blown into the molten metal to reduce impurities and **process** control the carbon content, transforming crude iron into steel. **Purity of steel** Need to inclusion Oxides (aluminum oxide), sulfides and silicates which can be done by vacuum remelting (tyhjiösulattamalla) or chemical reaction. **Ingots** (harkot) Processing into ingots is after steel is good quality and it's further formed into a finished product. Product is called Ingots when steel is casted into large block shapes. This material is often temporarily stored before being further processed or used. **Issues in formation** Are its shrinkage cavities which are hollow spaces formed due to shrinking of material when solidified. **Chemical segregation** which occurs when different chemical elements separate during solidification uneven chemical composition**. Slink holes** are air bubbles or voids caused my material shrinkage, resulting in porosity. **Pitting at the top of the mold** means uneven solidification which can cause surface depressions or pits on the ingot. **Solutions for formation** Shrinkage can be mechanically removed to improve ingots integrity. Elements like aluminum and silicon are added to reduce chemical segregation. Also, can do process where deoxidizing elements are added to reduce gas porosity and ensure uniform solidification which is called **killed steel**. **Continuous casting** Process takes place in water-cooled molds to maintain temperature control during solidification. It results in fewer material losses compared to traditional casting methods. The structure of the cast material is more homogeneous which leads to better consistency. Steel is called calmed when the steel is evenly cooled down with porosity distributed uniformly throughout the material. A hot jet is used to cut the steel into desired lengths. Fewer rollers are needed to shape and guide steel through the process. **Rolling** The steel runs between rollers with the distance between them gradually decreasing to shape the material into desired thickness. hot and cold rolling difference happens to grains in the steel. **Hot rolling** Deforming happens when warm and recrystallisation (uudelleen kiteytys) happens in 1000-1250 Celsius. Grains regrow when pressed together. Layer of dark oxidized metal forms to surface. **sheet, strip, rectangular bars, structural sections and tubes** **Cold rolling** Grains are flattened in cold deformation which means distorting crystals and therefore steel becomes harder, but more brittle (hauras). **Metal structure** When metal is liquid, the atoms do not occupy a fixed position in relation to each other and only happens when metal solidifies. In cooling grains of solid particles form liquid mass and in further cooling solid particles until filled which is called crystalline. Crystals atoms have fixed position in relation to each other aspects are determined by properties of metal. Structure: Solidification process atoms arrange themselves to certain regular patterns (*cubic body centered, cubic face centered, hexagonal*) Mixing crystals Structure of mixture of 2 metals (theoretical model). Mixture of crystals occurs if the added atoms of the metals are present in excess (yli) and form bonds with themselves. In the liquid state metals A and B dissolve, but on solidification state they separate. Different types of crystals can form. Alloys (metalliseokset). **Solidification point** Pure metals have fixed melting and solidification point. When the material is solidified it cools further. Alloys will go through this, but Molten metal will not follow a rectilinear path. There are 3 situations for this alloys whose metals are *soluble, insoluble or partially soluble* in solid state. **Stopping point** Moment in time where the metal will not cool or will cool less rapidly when solidifying. (raudan/hiilen seos) Steel is an alloy of iron and carbon. Alloy contains less than 0.005% carbon at room temperature and no other considered pure iron. It's soft, ductile and not very strong and therefore used in engineering applications(magnetic appl.).