Question

Steel design,

PROBLEMS 1-1 What is the steel and how can we change its properties? 1-2 What is the alloy steel? 1-3 What is the effect of increasing the percentage of carbon in steel? 1-4 Describe the process of quenching and tempering of steel. 1-5 What is the difference between anealing process and normalizing process? 1-6 What is the preferred type of steel to be used for C, L sections, plates and bars. 1-7 Which type of steel is used for plates only? 1-8 What are the jumbo sections? 1-9 What is the preferred steel type to be used for cold-formed HSS? 1-10 What is the steel type used for pipes? 1-11 What is the meaning of the following abbreviations: W610x92, C 230 x 22, L203x152x19, HSS 254x6.4? 1-12 What is the difference between standard, x-strong and xx-strong pipes? 1-13 What is the preferred type of steel used to produce W sections? 1-14 According to AISC specification, what is the difference between bar and plate?

Answer 1

1-1 Answer :

Steel : Steels are a large family of metals. All of them are alloys in which iron is mixed with carbon and other elements.Steel is an alloy of iron with typically a few percent of carbon to improve its strength and fracture resistance compared to iron. Steels are described as mild, medium- or high-carbon steels according to the percentage of carbon they contain, although this is never greater than about 1.5%.

Type of steel	% of carbon
Mild steel	up to 0.25%
Medium carbon steel	0.25% to 0.45%
High carbon steel	0.45% to 1.5%

To change the properties of a steel or metal, we have to change the microstructure of the metal. For a given alloy composition, there are two ways to change the microstructure:

1. Heat it

2. Beat it

  Changing the heat treatment of a steel will change the grain size, and the size, distribution, and morphology of the second phase particles, like carbides. Conducting cold working on a metal will increase the density of dislocations. Increasing the dislocation density of a metal will increase its yield strength, up to a point.

1-2 Answer :

Alloy Steel : Adding metals such as nickel, chromium, and tungsten to iron produces a wide range of alloy steels and also other elements comprising metals and non-metals are added to carbon steel, alloy steel is formed. The following are the types of alloy steel :

1. Low alloy steel

2. High alloy steel

1-3 Answer :

The floowing are the effects of increasing the percentage of carbon in steel :

• Increasing the percentage of carbon in steel increases hardness and strength and improves hardenability.
• Increasing the percentage of carbon in steel also decreases the plasticity and toughness.
• The lower the carbon content, the higher the plasticity and toughness of the steel.
• Increasing the percentage of carbon in steel increases brittleness and reduces weldability.

1-4 Answer :

  Quenching :

The process of quenching is also called as quench hardening. The process of quenching or quench hardening involves heating the material and then rapidly cooling it to set the components into place as quickly as possible. The process is tightly controlled, with the heating temperature, cooling method, cooling substance and cooling speed all dependent upon the type of material being quenched and the desired hardness. A typical heating range is between 815 and 900 degrees celcius, with extra care being taken to keeping the temperature as stable as possible. Variances in the degree of heat being applied during the process can result in distortion in the resultant metal.

Tempering :

After the material has been quenched to its hardest state, the process of tempering is used to achieve greater toughness and ductility by decreasing hardness. Tempering is achieved by heating the quenched material to below the critical point for a set period of time, then allowing it to cool in still air. Both the temperature and heating time depend on the composition of the material and will determine the amount of hardness removed.

1-5 Answer :

Difference between anealing process and normalizing process :

Anealing process : It is the process of heating a metal in a furnace above it's recrystallization temperature and allow it to cool inside the furnace. First the temperature of the material is raised (say 912–915°C for cast iron or steel). Secondly the material is soaked in that temperature for few hours. Third, the temperature is lowered and the material is allowed to cool inside the furnace. Annealing improves ductility, strength and good elongation properties.

Normalizing process : Normalizing process is similar to that of annealing, but after soaking stage the material is taken out from the furnace and allowed to cool in atmosphere. The properties of the material are bit lower than that of annealing because of different cooling areas in the material.

1-7 Answer :

A steel plate is a broad and generic term for steel in the form of a plate. However, steel can be combined with other metals to form alloys, which can make them corrosion resistant, stronger or lighter. In addition to what alloy of steel plate is made, the thickness can range from 3/16 inch to several inches.

Carbon Steel	A36, A572 GR 50, A588 (Corten type), 1045, A516 GR 70, A514 T-1
Carbon Alloy	4130, 4140, 4340
Abrasion Resistant	AR400, AR500
Other Grades	33Max, A285 GR C, A515 GR 70, ABS Grades, & AR360

1-8 Answer :

The following are the jumbo sections:

• Jumbo columns: AS/NZS 3679 hot rolled column sections are manufactured up to 310UC 158, a 327mm x 311mm column weighing 158 kg/m and a maximum flange thickness of 25mm. (1) .HL extra wide flanged beams. (2 ).HE wide flanged beams. (3) UB Universal Beams. (4) W wide flange beam
• Jumbo equal angles
• Jumbo hot rolled beams

1-10 Answer :

• Carbon steel and stainless steel is used for pipes.
• Carbon steel pipes and stainless steel pipes are most common type of stanadard pipes.