Архитектура Аудит Военная наука Иностранные языки Медицина Металлургия Метрология
Образование Политология Производство Психология Стандартизация Технологии
Fill in the gaps with the necessary prepositions.
1.17 Read the text again and choose the correct variant to the following:
1) What is the portion of the joint where the metals are closest to each other?
a groove; b) a root; c)a root opening; d)an included angle.
2) What configuration doesn’t the root have in the cross section?
a) line; b)point; c)curve; d)area.
3) The root edge
a) is basically a root face of zero width; b) is basically a groove face of zero width;
c) is basically a root face of two in. width;
d)is basically a root face of zero thickness.
4) A groove is
a) an opening or space provided under the edges of the metal parts to be welded;
b) an opening or space provided between the edges of the metal parts to be welded;
c) an opening or space provided between the edges of the metal parts to be cut;
d) an opening or space provided between the surface of the metal parts to be welded.
5) The bevel angle is the angle formed
a) between the weld reinforcement and a plane perpendicular to the surface of the member.
b) between the prepared edge of a member and a plane perpendicular to the surface of the member.
c) between the prepared edge of a member and a plane parallel to the surface of the member.
d) between the prepared edge of a member and a plane perpendicular to the centre line of the root cross section.
6) What is a groove angle? It is
a) the angle between the surface of the member and the plane perpendicular to the edge of it;
b) the prepared edge of a member and a plane perpendicular to the surface of the member;
c) the partial angle of the groove between the parts to be joined;
d) the total angle of the groove between the parts to be joined.
7) What is not necessary to consider to determine the bevel angle, groove angle and root opening for a joint?
a) the type of joint to be made; b) the thickness of the weld material;
c) the weld reinforcement; d) the welding process to be used.
8) Weld reinforcement is a term used to describe
a) weld metal in excess of the metal necessary to fill a joint;
b) the filler metal used to make up a weld;
c) the molten metal necessary to fill a joint;
Scan the text and fill in the left part of the table using the information from the text. Find the information in the Internet and your textbooks to fill in the right part.
Before reading the text “Heat-affected zone” try to answer the following questions.
What in your opinion influences the heat-affected zone?
What are the characteristics of the process of shielded metal arc welding?
What are the characteristics of the process of gas metal arc welding?
What are the characteristics of the process of submerged arc welding?
What are the characteristics of the process of gas tungsten arc welding?
How do these characteristics influence the heat-affected zone?
Read the text “Heat-affected zone” paying attention to the active terminological vocabulary to check if your predictions were correct.
The zone of interest for the welder is the heat-affected zone. This zone includes that portion of the base metal that has not been melted; however, the structural or mechanical properties of the metal have been altered by the welding heat. Because the mechanical properties of the base metal are affected by the welding heat, it is important that you learn techniques to control the heat input. One technique often used to minimize heat input is the intermittent weld. In the picture you can see the HAZ of a pipe weld, with the blue area being the metal most affected by the heat.
Zones in a weld.
The effects of welding on the material surrounding the weld can be detrimental—depending on the materials used and the heat input of the welding process used, the HAZ can be of varying size and strength. The thermal diffusivity of the base material plays a large role—if the diffusivity is high, the material cooling rate is high and the HAZ is relatively small. Conversely, a low diffusivity
leads to slower cooling and a larger HAZ. The amount of heat injected by the welding process plays an important role as well, as processes like oxyacetylene welding have an unconcentrated heat input and increase the size of the HAZ. Processes like laser beam welding give a highly concentrated, limited amount of heat, resulting in a small HAZ. Arc welding falls between these two extremes, with the individual processes varying somewhat in heat input. To calculate the heat input for arc welding procedures, the following formula can be used: , where Q = heat input (kJ/mm), V = voltage
(V), I = current (A), and S = welding speed (mm/min). The efficiency is dependent on the welding process used, with shielded metal arc welding having a value of 0.75, gas metal arc welding and submerged arc welding, 0.9, and gas tungsten arc welding, 0.8.
Последнее изменение этой страницы: 2016-03-15; Просмотров: 165; Нарушение авторского права страницы