ENGINEERING MATERIALS molybdenum (0.5% to 0.8%) to make molybdenum steel. is generally used with chromium and manganese Mo increase hardenability and strength Mo-carbides help increase creep resistance at elevated temps typical application is hot working tools It can replace tungsten in high speed steel. 8. Silicon: It increases the strength and hardness of steel without lowering its ductility. Silicon steel containing from (1% to 2% silicon and 0.1% to 0.4% carbon) have good magnetic properties and high electrical resistance. It can withstand impact and fatigue even at elevated temperature. These steel are used for generator and transformers in the form of laminated cores. University of Baghdad / Mechanical Engineering Department Dr. Suhair G. Hussein 14 ENGINEERING MATERIALS Tool Steel Introduction: These are the steel used in making tools and dies which are required for cutting, shaping, forming, and blanking of materials.

These resistance, conductivity, low coefficient of friction. steels should have high hardness, greater abrasion or wear thermal impact greater toughness, high strength, high Types of tool steel: The tool and dies steels are of the following types:1. Plain carbon steels: These steels contain carbon from (0.60% to 1.4%) and are hardened either by oil or water quenching. The important advantage of these steel is that they low cost, good machinability, and high impact resistance. The main disadvantage of carbon tool steel is poor hardenability. It needs quenching with water, brine or caustic water. Distortion and cracking tend to be large, and wear resistance and thermal strength are very low. Therefore, carbon to make small tool steel can only be used handmade tools or woodworking tools, as well as small cold working dies with low precision, simple shape, small size and light load. These steels are used for: keys, stamping dies, twist drills, general

University of Baghdad / Mechanical Engineering Department Dr. Suhair G. Hussein 15 ENGINEERING MATERIALS wood and leather cutting tools. Plain carbon tool steel 2. Low alloy tool steel: These vanadium, alloying chromium, tungsten, and silicon. The presence of alloying elements impact increases refine resistance. Compare with carbon tool steel, its hardness, toughness and wear-resistance are raise. And its hardenability and hot hardness are raised dramatically. steels containing elements like: the structure and the toughness and University of Baghdad / Mechanical Engineering Department Dr. Suhair G. Hussein 16

ENGINEERING MATERIALS The low alloy tool steel are used for heavy duty pneumatic tools, pavement breakers. it was used to make measuring tools, molds and blade tools with big size, complex shape and high requirement of performance. Different levels for alloy steel because of the different total amount of alloy elements. And if the alloy elements amount is less than 5%, then it is low alloy tool steel. The medium alloy tool steel is at the range of 5%-10%. And the high alloy tool steels are higher than 10%. At the present time, most of the alloy tool steel is low alloy tool steel. 3. High speed steels: