Alloying in Steel

Alloying in SteelAlloy SteelHigh Strength, Low Alloy (HSLA)Kelompok 3Patricia BagusAlviNurulAiprijalAnam

introductionKeterbatasan Baja Karbon:a) A high critical cooling rate which leads to cracking when quenching hardening.b) Poor Hardenability.c) Ultimate Tensile Strength rendahJika di Heat Treatment Elongasi RendahToughness Rendahd) Ketahahan Korosi (Corrosion Resistant) RendahKetahanan Aus (Wear Resistant) RendahKetahanan Panas (Heat Resistant) RendahPlain carbon steel (non alloyed), numberof alloying elements is very limited: Manganese: 1.00% max Sulfur 0.05% max Phosphorus 0,04% max Silicon 0,03% max

Alloy Steel : campuran antara baja karbon dgn unsur-unsur lain. Paduan ini mempengaruhi sifat mekanik, kecepatan membeku, titik cair, dan bertujuan memperbaiki kualitas dan kemampuannya

Why are metals treated further after casting?

to modify the microstructure.The real importance of alloys is that they can be designed to have properties for specific uses.In the alloy, some of the added ions may be larger than most of the ions making up the metal lattice. They disrupt the regular arrangement of ions and make it more difficult for the layers to slide over each other. This makes the alloy harder and less malleable and ductile than the pure metal (in which the layers slip over each other more easily).

Improving mechanical properties by increasing the depth to which a steel can be hardened (hardenability) allows advantage of tempered martensitic throughout allows slower quench To allow higher tempering temperatures while maintaining high strength and good ductilityImproving strength at room temperatureImproving mechanical properties at high and lowtemperatures Improving corrosion resistance and elevatedtemperatureoxidationImproving special properties such as abrasion resistance and fatigue behavior Improving magnetic propertyPenambahan unsur paduan pada baja memberikan pengaruh yang signifikan terhadap diagram fasa Fe Fe3CPengaruh tersebut dapat merubah batas fasa dan ukuran daerah fasa pada diagram fasa Fe Fe3C, hal tersebut bergantung pada jenis unsur paduan dan konsentrasi unsur paduan yang ditambahkan pada bajaFerrit Stabilizer: biasanya ferrit akan bertransformasi menjadi austenite pada suatu temperature tertentu, temperature transformasi akan naikAustenite stabilizer: unsur paduan yang membuat austenite menjadi lebih stabil pada tempertatu lebih rendah.Carbide forming element: karbida yang terbentuk ini dapat berupa karbida sederhana/kompleks. Dengan adanya karbida, akan menaikkan sifat tahan ausCarbide stabilizer: unsur paduan yang membuat karbida lebih stabil, tidak mudah terurai/ larut ke dalam suatu fase.Nitride forming element: dengan adanya nitriding, akan menaikkan kekerasan.

Pengaruh pada ferriteNickel, aluminium, silicon, copper and cobalt are group 1 elements and are found largely dissolved in ferrite. In the absence of carbon, considerable proportions of the group 2 elements will be found dissolved in ferrite. Manganese, chromium, tungsten, molybdenum, vanadium and titanium are group 2 elements. The carbide forming tendency is apparent only when there is a presence of significant amount of carbon. Any element dissolved in ferrite increases its hardness and strength in accordance with the general principles of solid solution hardening. The figure given below shows probable hardening effect of the various elements dissolved in alpha iron. Pengaruh pada carbideAll carbides found in steel are hard and brittle, their effect on the room-temperature tensile properties is similar regardless of the specific compositionchromium and vanadium carbides are outstanding in hardness and wear resistanceThe hardness and wear resistance of alloy steels rich in carbides are in a large measure determined by the amount, size and distribution of these hard particles. These factors, in turn, are controlled by chemical composition, method of manufacturing and heat treatment. The presence of elements that form carbides influences the hardening temperature and soaking time. The carbide-forming elements are very powerful deep-hardening elements when they are dissolved in austenite.