Terminology and standard
Để đọc và dịch Tiếng Anh chuyên ngành hàn hiệu quả, việc nắm vững các thuật ngữ, ký hiệu viết tắt về phương pháp hàn, cũng như các tiêu chuẩn và quy phạm kỹ thuật là rất quan trọng.
- Đọc hiểu các thuật ngữ trong ngành hàn bằng Tiếng Anh;
- Đọc hiểu các ký hiệu viết tắt Tiếng Anh về các phương pháp hàn;
- Đọc hiểu các tiêu chuẩn, quy phạm kỹ thuật Tiếng Anh trong cơ khí nói chung và ngành hàn nói riêng;
- Dịch các tài liệu tiếng việt về thuật ngữ hàn sang Tiếng Anh
- Welded joint: Liên kết hàn
- Welding process: Quy trình hàn
- Welding structure: Kết cấu hàn
- Clamp: Kẹp lại, giữ lại
- Base metal: Kim loại cơ bản
- Amperage: Cường độ dòng điện
- Base metal: Kim loại cơ bản - Kim loại hoặc hợp kim được hàn hoặc cắt
In chemistry, base metals are defined as metals that oxidize or corrode easily and react variably with diluted hydrochloric acid (HCl) to produce hydrogen Common examples of base metals include iron, nickel, lead, and zinc While copper is also classified as a base metal due to its propensity to oxidize, it does not react with hydrochloric acid.
- Welding process: Quá trình Hàn - Tập hợp các nguyên công cơ bản được sử dụng trong hàn, cắt bằng nhiệt hoặc phun phủ bằng nhiệt
According to AWS, welding is a materials joining process that creates coalescence through heating materials to appropriate temperatures, either with or without pressure, and may involve the use of filler material.
A welded joint is a connection formed through the welding process, where two or more metallic components are joined by introducing fused metal, such as a welding rod, into the fillet between them This can also be achieved by raising the temperature of the surfaces or edges to their fusion temperature and applying pressure, a method known as flash welding.
- There are many different kinds of welding machines nowsaday
- Several approaches have been developed to analyze welding structures
S + Be + V_ ed ( past participle) + (by….)
The passive voice is constructed by using the appropriate form of the verb "to be" that matches the tense of the active verb, followed by the past participle of the main verb.
In passive voice constructions, the subject of the active verb is referred to as the 'agent' of the passive verb Typically, the 'agent' is omitted, but when included, it is introduced by the word 'by' and positioned at the end of the clause.
E.g:This metal of plate was welded by my father
- Passive voice is used when the focus is on the action It is not important or not known, however, who or what is performing the action
Active: We build this bridge
Passive: This bridge is built
Active: They broke the window
Passive: The window was broken
2.3 The passive of continuous tenses
S + is / are + being + V_ ed ( past participle)
Active: they are repairing the bridge
Passive: The bridge is being repaired
S + should / can + be + V_ ed ( past participle)
Active: You should shut these doors
Passive: These doors should be shut
The process allows for the deposition of metal to create surfaces with alternative properties This technique can be utilized to enhance the characteristics of materials, offering diverse applications in various industries.
This lesson outlines a method for welding two metal pieces into a single solid unit By concentrating the heat from an electric arc on the edges of the metals, they melt, and additional molten metal is introduced As this mixture cools, it solidifies, resulting in a strong, unified piece.
An electric arc is created between the electrode, a small metal wire held in a hand-held holder, and the base metal being welded By maintaining a gap of 1/16" to 1/8" between the electrode tip and the workpiece, the electric current jumps across this space to form an arc This arc is then moved along the joint, effectively melting the metal as it progresses.
Arc welding is a manual skill requiring a steady hand, good general physical conditions, and good eyesight The operator controls the welding arc and, therefore, the quality of the weld made
Figure 3 Illustrates the action that takes place in the electric arc It closely resembles what is actualy seen during welding
The "arc stream" visible in the center of the image represents the electric arc generated by the flow of electric current between the electrode's tip and the workpiece With temperatures reaching approximately 6000°C, this arc is capable of melting metal Its intense brightness and heat make it hazardous to view directly, as doing so can result in painful, albeit typically temporary, injuries.
The arc welding process melts the base metal, creating a molten pool that resembles a crater, similar to how water from a garden hose can erode the earth As the molten metal flows away from the arc, it cools and solidifies, while a protective slag forms on top of the weld during the cooling process.
Welding machines come in various types, including motor-generators, engine-driven generators, transformers, rectifiers, and combination transformer-rectifiers, each serving a specific purpose Their primary function is to provide a controlled source of electric power for welding, characterized by high amperage at low voltage This high amperage is essential for generating sufficient heat at the arc, while the voltage remains low enough for safe handling and high enough to sustain the arc Additionally, these machines allow operators to control the current, which directly influences the arc's heat, and some models enable the selection of either a forceful or soft arc, tailoring its characteristics to meet specific job requirements.
- A gap is made in the welding circuit
- The quality of the weld made
- Flow away from the arc
1.Give main ideas of the paragraph?
3.What happens in the arc?
4.What do the electrodes affect to the arc?
5.Name some types of welding machines?
These are some standards that are used for welding 1 ASME (American society of machanical engineers): include:
2.ASME boiler& pressure vessel code
3.ASME code for pressure piping
5.AWS D1.1- steel structural welding code
7.API 650 – welding storage tanks for oil storage
8.API 1104 – welding of pipelines and related facilities
- welding storage tanks - welding of pipelines
1 List and explain the uses of the standards?
Welded joint and weld
Liên kết hàn là sự kết nối giữa các vật liệu, chủ yếu là kim loại, thông qua quá trình hàn Có năm loại liên kết hàn cơ bản: giáp mối, chữ T, chồng, góc và mép Liên kết hàn không chỉ bao gồm phần kim loại của mối hàn mà còn bao gồm vùng ảnh hưởng nhiệt và phần kim loại cơ bản xung quanh, nơi có ứng suất và biến dạng khác biệt so với phần còn lại của kim loại.
- Đọc hiểu các thuật ngữ trong ngành hàn bằng Tiếng Anh ;
- Đọc hiểu các liên kết mối hàn, đường hàn bằng Tiếng Anh;
- Thực hành đọc hiểu các tài liệu Tiếng Anh về liên kết mối hàn;
- Dịch các tài liệu Tiếng Việt về thuật ngữ hàn sang Tiếng Anh
- Welding position : Vị trí hàn
- Butt joint: Liên kết giáp mối
- Corner joint: Liên kết góc
- Lap joint: Liên kết chồng
- Tee joint: Liên kết chữ T
- Edge joint : Liên kết cạnh
- Butt weld: Mối hàn giáp mối
- Fillet weld: Mối hàn góc
- Groove weld: Mối hàn giáp nối có vát mép
- Spot weld: Mối hàn điểm
- Configuration : Hình dạng, Hình thể
- Weld reinforcement: Độ lồi mối hàn
- Weld concavity: Độ lõm mối hàn
- Weld width: Chiều rộng mối hàn
- Leg of a fillet weld: Chiều cao mối hàn góc
- Sealing run: Mối hàn lót
Vị trí hàn là mối quan hệ giữa vũng hàn và các phần tử liên kết với nguồn nhiệt hàn Các loại vị trí hàn bao gồm hàn bằng, hàn ngang, hàn đứng và hàn trần, mỗi loại có đặc điểm và yêu cầu kỹ thuật riêng.
+ Flat Welding Position; Horizontal Welding Position; Vertical Welding
- Butt welds: are welds where two pieces of metal are joined at surfaces that are at 90 degree angles to the surface of at least one of
Weld reinforcement refers to the protruding metal of a weld that extends beyond the required dimensions of a joint, such as a butt or fillet weld This excess weld metal is added to ensure adequate filling of the joint, enhancing the overall strength and durability of the welded structure.
- weld defects, concavity, weld gap, torch offset, tailored blank laser established according to the analysis of reasons causing weld concavity
- When you start getting right into welding, you will eventually need to know what all the different welding positions
- A fillet weld is a means of connecting two pieces of metal at a 90° angle - The fifth major type of welding connection is the corner joint
- Short adjectives: are short words which have only one syllable E.g: high, small, big, nice, hot
- Long adjectives: are long words which have more than one syllables E.g: expensive, beatilful, difficult
- This metal is stronger than that kind
- Overhead welding is more difficult than flat welding
- This welding position is the most difficult
- That butt weld is the most beautiful of all
* Notes on the comparison of shorter adjectives * Spelling of comparative and superlative forms:
- Most one-syllable adjectives form their comparatives and superlatives like clean: -er and –est are added to their basic form
- Many one-syllable adjectives end with a single consonant after a single vowel-letter This consonant doubles in the comparative and superlative, as in the case of big: bigger, biggest
- Many one-syllable adjectives end in –e, like nice or safe These add –r and –st to the basic form: safer, safest
- Some adjectives, like dry, end in –y with a cosonant letter before it These adjectives are usually two-syllable In the comparative and superlative –y is replaced by i: drier, driest
Most longer adjectives combine with quantifiers more / less to form their comparatives and most / least to form their superlatives
Ex: This joint is more beautiful than that one
This position is the most difficult job when welding a fabrication
- A compound noun is a noun that is made up of two or more words Most compound nouns in English are formed by nouns modified by other nouns or adjectives
Noun + Noun/ Adjective + Noun Ex: butt joint, lap joint, classroom, hard metal, sharp edge
There are numerous types of welded joints and various positions in which they are welded Figure below shows a variety of these joints as they may appear on welding jobs
Welding can be performed in four primary positions: Flat (F), Vertical (V), Overhead (OH), and Horizontal (H) While any joint can be welded in any position, the flat position is preferred whenever feasible due to its speed and ease of execution.
A summary of the basic types of joints and basic types of welds is shown in figure below
In welding, joints such as butt, T, corner, lap, and edge joints allow adjoining members to connect in various configurations While these joint geometries provide a general framework, the specific weld joint configuration can vary significantly For example, a weld butt joint can be crafted in multiple styles, including square, double-square, single-bevel, double-bevel, single-V, double-V, and several other configurations Similarly, a T connection can utilize a double fillet or be formed with single or double-bevel or J joints Notably, V and U weld joints are primarily applicable to butt and corner welds due to the necessity of preparing both surfaces involved.
1.How many types of welded joints are there?
2.How many types of welding positions are there?
3.Which welding position is the easiest?
4.How can a weld butt joint be made?
1.What is the difference between Fillet Weld and Square Weld ?
2.What is the difference between Bevel Groove Weld and Vee Groove Weld?
3.What is the difference between J Groove Weld and U Groove Weld?
Imperfection welding
Mối hàn có nhiều loại khuyết tật do nhiều nguyên nhân khác nhau, liên quan đến kim loại hàn, chế độ hàn và quy trình công nghệ Những khuyết tật này ảnh hưởng trực tiếp đến độ bền của đầu mối hàn Vì vậy, thợ hàn cần chọn quy phạm hàn chính xác và tuân thủ nghiêm ngặt các quy trình hàn để đảm bảo chất lượng.
- Đọc hiểu các thuật ngữ trong ngành hàn bằng Tiếng Anh;
- Đọc hiểu các ký hiệu về khuyết tật trong Tiếng Anh;
- Thực hành đọc hiểu các tài liệu Tiếng Anh về các khuyết tật về mối hàn;
- Dịch các tài liệu Tiếng Việt về thuật ngữ khuyết tật hàn sang Tiếng Anh
- Pit, surface pore: Rỗ bề mặt
- Incomplete joint: Hàn không ngấu
- Incomplete fusion: Hàn không ngấu
- Weld crack: Vết nứt mối hàn
- Transverse crack: Vết nứt ngang
- Underbead crack: Vết nứt dưới lượt hàn
- Toe crack: Vết nứt chân mối hàn
- Hot crack: Vết nứt nóng
- Cold crack: Vết nứt nguội
- Reheat crack: Vết nứt gia nhiệt
- Root crack: Vết nứt đáy mối hàn
- Crater crack: Vết nứt hố
- Lamellar tear: Vết tách lớp
- Sub-surface: Bề mặt nhỏ
- Fatigue life: Sức bền, sự chống chịu
- In service: Trong thời gian sử dụng, trong khi sử dụng
- Adjacent: Lân cận, gần kề
- Elongate: Giãn ra, kéo dài ra, nối dài
- Solidification: Sự cứng lại, sự đông đặc, sự hóa rắn
- nozzle: Đầu phun, khe mở
- Incomplete fusion: Hàn không ngấu sinh ra ở góc mối hàn, mép hàn hoặc giữa các lớp hàn Phần lớn kết cấu bị phá huỷ đều do hàn không ngấu
Incomplete fusion in welding results from inadequate integration between the weld metal and adjacent weld beads This issue can arise due to several factors, including poor operator technique, improper base metal preparation, insufficient welding heat, limited access to adjoining beads, and flawed joint design.
- Weld crack: Nứt mối hàn là các vết nứt tạo ra trong mối hàn
The cracking is the result of solidification, cooling, and the stresses that develop due to weld shrinkage
- Slag inclusion: Lẫn xỉ là hiện tượng xỉ còn lẫn lại trong kim loại đắp hoặc vùng nóng chảy với kim loại cơ bản
Slag inclusions are nonmetallic solid material entrapped in weld metal or between weld metal and base metal
Rỗ khí là hiện tượng xảy ra khi khí trong kim loại không kịp thoát ra trước khi kim loại đông đặc, dẫn đến sự hình thành các lỗ rỗng Hiện tượng này có thể xuất hiện cả bên trong và trên bề mặt mối hàn, ảnh hưởng đến chất lượng và độ bền của sản phẩm kim loại.
Cavities can arise from two main causes: gas entrapment or shrinkage during solidification Gas cavities occur when gas becomes trapped within a material, while shrinkage cavities are a result of the material contracting as it solidifies Understanding these types of cavities is crucial for improving material quality and performance.
Gas pore Worm hole Surface pore
- Incomplete fusion is caused by faulty operator technique
- Crater cracks occur when a crater is not filled before the arc is broken
2 GRAMMAR: THE ARTICLE - A / AN AND THE
The form a is used before a word beginning with a consonant, or a vowel with a consonant sound:
Example: a steel a bar of steel a joint The form an is used before words beginning with a vowel ( a, e, i, o, u) or words beginning with a mute h:
Example: an iron an imperfection an irregular or individual letters spoken with a vowel sound:
A/ an is used before a singular noun which is countable when it is mentioned for the first time and represents no particular person or thing:
Example: a butt joint a lap joint a position a way
The definite article is used before a noun which has become definite as a result of being mentioned a second time:
There is a student repairing electric in the shop The student that you asked to help me yesterday And before a noun made definite by the addition of a phrase or clause:
The body of the weld The area of the arc strike The damage on the parent material
At the end of The side of the weld
Fill each blank with „a', „an', „the' or leave it blank
1 He left _ home without informing anyone
2 There is _ box of electrodes on _ table
3 Do you need _ degree in Economics or _ degree in finance to be a better manager?
4 When we arrived, she went straight to _ welding cabin and started to prepare _ base metals to weld
5 He has _ cut on his leg and _ bruise on _ chin
6 _ Mt Everest is _ highest mountain in _ world
7 Switch off _ air-conditioner please I have _ cold
8 We reached _ top of _ hill during _ afternoon
9 Do you like _ weather here? Isn't it too hot during _ day but it is very cold at _ night?
10 _ attempt has been made to collect _ funds to start _ public welding association in _ town where I live
3.1 External defects: Defects detected by surface inspection 3.1.1 Undercut
An irregular groove at the toe of a weld joint, whether in the parent metal or in previously deposited weld metal, can create a sub-surface defect that acts as an effective slag trap within the weld This undercut essentially forms a notch, which serves as a focal point for stress loading and significantly reduces the fatigue life of the joint.
Causes - current too high, voltage too high, travelspeed too high, electrode too small, electrode angle
A crack is a linear discontinuity produced by fracture Cracks may be longitudinal, transverse, edge, crater, centreline, fusion zone, underbead, weld metal or parent metal (Figure 5 -7)
Longitudinal, in the weld metal (centreline) Longitudinal, in the parent plate
An imperfection at the toe or root of a weld caused by weld metal flowing on to the surface of the
Causes - slow travel speed, large electrode, tilt angle, poor pre-cleaning
The failure of weld metal to penetrate the root of the weld can be attributed to several factors, including inadequate weld preparation, an excessively small root gap, a root face that is too large, a small included angle, and insufficient heat input.
Lack of union at the root of a joint
Causes - poor weld prep, uneven bevel, root face too large, linear misalignment
Excess weld metal protruding through the root of a fusion weld made from one side only Causes - high heat input, poor weld prep - large included angle
Root concavity (suck-back, underwashing)
A shallow groove which may occur in the root of a butt weld
Causes - purge pressure, wide root gap, and residual stresses in root
2.How does the undercut affect the jont?
3.What are the causes of the undercut?
4.What is an overlap? What are the causes of the overlap?
5.What is a crack? How many types of cracks are there?
6.How many types of root defects are there? What are the causes of root concavity?
* Definition of lack of fusion
Lack of fusion in welds refers to incompletely fused spots where the weld does not bond properly with the parent metal or a previous weld bead These adhesion joints can be surprisingly strong, resembling brazed joints or those formed through metallization However, the purer the lack of fusion, the more challenging it becomes to detect.
With regard to the position of the lack-of-fusion defects in a weld, three types of lack of fusion are distinguished:
1.lack of side-wall fusion,
2.lack of inter-run fusion,
3.lack of fusion at the root of the weld
The appearance of fracture faces can reveal two types of lack of fusion defects: those caused by unmelted oxide inclusions, which consist of oxides and non-metallic materials, and those due to melted oxide inclusions According to IIW references 4011, 4012, and 4013, three distinct types of lack of fusion exist, which should not be confused with lack of penetration, referenced as IIW 402 Surface defects are effectively identified through visual inspection, while internal lack of penetration in welds requires advanced detection methods such as X-ray or ultrasonic inspection.
Lack of fusion defects can be categorized into two main types: one type involves voids or non-metallic inclusions that can be identified using non-destructive testing methods, while the other type is characterized by structural defects that do not present any visible discontinuities in the material, making them undetectable through non-destructive techniques Understanding these characteristics is crucial for effective detection and assessment of fusion-related issues in materials.
It was found in metallographic examinations that in a weld three types of lack of fusion can be found:
1.pure lack of fusion or lack of fusion due to melted oxide inclusions,
3.lack of fusion consisting of non-metallic inclusions
A pure lack of fusion is a structural defect that occurs when molten metal adheres to the parent metal, which has not sufficiently melted during welding, resulting in a joint between the solid and liquid phases similar to a brazed joint This defect is not detectable through non-destructive testing methods and requires microscopic inspection for identification A straight fusion line may indicate potential lack of fusion between the parent metal and the weld, while inter-run lack of fusion is even less visible, only identifiable through precise microscopic examination at 50-times magnification.
Fig 10: Pure lack of fusion between the final run and the parent metal a) macrograph: x3.5; micrograph: x100
Weld solidification and cooling generate internal stresses that can cause the welded faces to separate, resulting in a small void measuring just a few hundredths of a millimeter This gap, resembling a crack, can be identified through non-destructive testing methods However, distinguishing this type of lack of fusion from a crack can be challenging An illustration of open lack of fusion is provided in Fig 11.
Fig 11: Open lack of fusion between the central and final runs a) macrograph, x3.5; b) micrograph: x100
The presence of lack of fusion often correlates with the occurrence of oxides and non-metallic inclusions As illustrated in Fig 12, if the oxide layer remains unmelted, these inclusions are evenly spread across the surface of the defect Conversely, when the oxide layer melts, the non-metallic inclusions transform into a spherical shape.
Fig 12: Inclusions at the faces sticking together a) The macrograph shows lack of fusion between the central and final runs; b) The micrograph shows inclusions at the faces sticked together
* Location of lack-of-fusion defects
Lack of fusion is a planar defect that can occur at the edge of the parent metal or between weld runs When it happens between the parent metal and the weld metal, it presents a flat face, while inter-run fusion defects exhibit an irregular shape Typically, lack of fusion is found within the weld itself and seldom affects the final runs or the root run For a visual representation of common lack of fusion types, refer to Fig 13.
Definition: A depression left at the termination of the weld where the weld pool is left unfilled Cause: Improper weld termination techniques
Repair: If no cracks exist, simply fill in the crater Generally welding from beyond the crater back into the crater
Definition: A crack running in the direction of the weld axis May be found in the weld or base metal
Cause: Preheat or fast cooling problem Also caused by shrinkage stresses in high constraint areas
Prevention: Weld toward areas of less constraint Also preheat to even out the cooling rates Repair: Remove and reweld
Definition: A crack running into or inside a weld, transverse to the weld axis direction
Cause: Weld metal hardness problem Crater Crack
Definition: A crack, generally in the shape of an ―X‖ which is found in a crater Crater cracks are hot cracks
Cause: The center of the weld pool becomes solid before the outside of the weld pool, pulling the center apart during cooling
Prevention: Use crater fill, fill the crater at weld termination and/or preheat to even out the cooling of the puddle
Definition: A longitudinal crack located in the weld throat area
Transverse stresses, often caused by shrinkage, can indicate inadequate filler metal selection or welding procedures and may lead to crater crack propagation To prevent these issues, it is essential to address the initial causes, such as increasing preheat and ensuring that no craters are left behind Additionally, using a more ductile filler material can help mitigate these stresses effectively.
Repair: Remove and reweld using appropriate procedure Be sure to correct initial problem first
Fig 1 3 : Lack of fusion in a weld: lack of side - wall fusion (above), lack of inter - run fusion (below)
Definition: A crack in the base metal beginning at the toe of the weld
Cause: Transverse shrinkage stresses Indicates a HAZ brittleness problem
Prevention: Increase preheat if possible, or use a more ductile filler material Root Crack Definition: A crack in the weld at the weld root
Cause: Transverse shrinkage stresses Same as a throat crack
Prevention: Same as a throat crack Underbead Crack
Definition: A crack in the unmelted parent metal of the HAZ
Prevention: Use LOW HYDROGEN electrodes and/or preheat Repair:
(only found using NDT) Remove and reweld Hot Crack
Definition: A crack in the weld that occurs during solidification
Cause: Micro stresses from weld metal shrinkage pulling apart weld metal as it cools from liquid to solid temp
Prevention: Preheat or use a low tensile filler material
Repair: Remove and reweld, correct problem first, preheat may be necessary, increase weld size
Definition: A crack that occurs after the metal has completely solidified
Cause: Shrinkage, Highly restrained welds, Discontinuities
Prevention: Preheat, weld toward areas of less constraint, use a more ductile weld metal
Repair: Remove and reweld, correct problem first, preheat may be necessary
Take precautions to prevent reoccurrence
Generally required to repair using a smaller electrode
3.2.3 Porosity A group of gas pores
Elongated cavities A string of gas pores situated parallel to the weld axis
A cavity generally over 1.5mm in diameter formed by entrapped gas during the solidification of molten metal
Wormhole An elongated or tubular cavity formed by entrapped gas during the solidification of molten metal
Porosity in welding occurs when dissolved gases or gases released during the welding process become trapped in the metal before solidification, leading to defects This can manifest as spherical porosity, characterized by rounded holes, or as elongated defects known as wormholes or piping Various factors contribute to the formation of porosity during welding.
- excessively long or short arc length
- insufficient or moist shielding gas
- base metal covered with oil, grease, moisture etc
- wet, unclean or damaged electrodes
Welding technology
Hàn là quy trình công nghệ sản xuất kết cấu không thể tháo rời từ kim loại, hợp kim và các vật liệu khác Phương pháp hàn nóng chảy cho phép liên kết hầu hết các kim loại và hợp kim với độ dày đa dạng Ngành hàn đã chứng kiến những bước tiến lớn trong công nghệ, với các phương pháp hiện đại ngày nay đạt hiệu quả tinh vi và chất lượng hàn cao.
- Đọc hiểu các thuật ngữ trong ngành hàn bằng Tiếng Anh;
- Thực hành đọc hiểu các tài liệu Tiếng Anh về các phương pháp hàn mối hàn;
- Thực hành giao tiếp thuyết trình nguyên lý vận hành các phương pháp hàn;
- Dịch các tài liệu Tiếng Anh về thuật ngữ phương pháp hàn từ Tiếng Anh sang Tiếng Việt và từ Việt sang Anh
- Mechanized welding : Hàn cơ giới
- Automated welding : Hàn tự động
- Fusion welding: Hàn nóng chảy
- Arc welding: Hàn hồ quang
- Arc welding using a consumable electrode: Hàn hồ quang dùng điện cực nóng chảy
- Arc welding using non-consumable electrode: Hàn hồ quang dùng điện cực không nóng chảy
- Submerged arc welding: Hàn dưới lớp thuốc (Hồ quang chìm)
- Gas shielded arc welding: Hàn hồ quang trong môi trường khí bảo vệ
- TIG (Tungsten inert gas welding): Hàn điện cực wonfram trong môi trường khí trơ (Hàn điện cực không nóng chảy trong mội trường khí bảo vệ)
- MIG – Metal inert gas welding: Hàn điện cực nóng chảy trong mội trường khí trơ
- MAG – Metal active gas welding: Hàn điện cực nóng chảy trong mội trường khí hoạt tính
-Self-shielded arc welding: Hàn hồ quang tự bảo vệ
-Pulsed arc welding: Hàn hồ quang xung
-Manual arc welding: Hàn hồ quang tay
-Automatic arc welding: Hàn hồ quang tự động
- Double arc welding: Hàn hai hồ quang
- Multi-arc welding: Hàn nhiều hồ quang
- Twin electrode welding: Hàn 2 que hàn
-Semi-automatic arc welding:Hàn bán tự động
- Electroslag welding: Hàn điện xỉ
- Resistance welding: Hàn tiếp xúc
- Resistance seam welding: Hàn đường
- Step-by-step welding: Hàn bước
- Spark gap: điện Bộ phóng điện, khe đánh lửa, khe phóng
- Stainless steel: Thép không gỉ
Hàn hồ quang tay, hay còn gọi là hàn que, là quá trình hàn điện nóng chảy sử dụng que hàn có vỏ bọc mà không cần khí bảo vệ, với tất cả các thao tác do thợ hàn thực hiện bằng tay Trong khi đó, hàn hồ quang plasma (PAW) là một quy trình tương tự như hàn điện cực nóng chảy trong môi trường khí bảo vệ (GTAW), sử dụng điện cực không nóng chảy bằng vonfram Quá trình này diễn ra trong một buồng khí kim loại được làm mát bằng nước, với phần cột hồ quang nằm bên trong và kết thúc bằng một lỗ phun hình trụ đồng trục với điện cực.
Plasma arc welding (PAW) is an advanced arc welding technique akin to gas tungsten arc welding (GTAW), characterized by the creation of an electric arc between a tungsten electrode and the workpiece Unlike GTAW, PAW positions the electrode within the torch body, allowing for the separation of the plasma arc from the shielding gas envelope This process involves directing the plasma through a fine-bore copper nozzle, which constricts the arc and enables the plasma to exit at high velocities, enhancing the welding efficiency and precision.
Plasma Arc Welding (PAW) is an advanced welding technique that operates at speeds nearing the speed of sound and temperatures around 20,000 °C Utilizing a non-consumable tungsten electrode, PAW features an arc that is precisely constricted through a fine-bore copper nozzle This innovative process is capable of joining all metals that can be welded using Gas Tungsten Arc Welding (GTAW), making it suitable for most commercial metals and alloys.
Protecting fresh welds from contamination is crucial, necessitating the use of gas to shield against atmospheric elements and impurities on the steel, including oil and paint In industries like shipbuilding, the manual welding techniques employed differ significantly from those utilized in skyscraper construction.
TIG welding, which gained popularity in the early 1940s, has significantly advanced the use of aluminum in welding and structural applications This method is favored for its ability to produce high-quality welds and is often performed manually The process involves creating an arc between a pointed tungsten electrode and the workpiece, facilitating precise welding.
2 GRAMMAR: Passive voice with modal verbs ( be continued )
- The passive voice with may, can, should and must
The process enables the deposition of metal to create surfaces with alternative properties This technique can also be utilized to achieve similar results in surface modification.
Active: The welder may use this parent metal
Passive: This parent metal may be used by the welder
Active: You should shut these doors Passive: These doors should be shut
Active: The operator must check the base metals before welding
Passive: The base metals must be checked before welding by the operator
Shielded metal arc welding (SMAW), also known as manual metal arc (MMA) welding, flux shielded arc welding, stick, and electric arc welding is a constant current drooping arc process (Figure 17)
Manual metal arc welding utilizes an electric arc as its heat source, created between a consumable electrode and the parent plate This arc is initiated by briefly touching the electrode's tip to the plate, then lifting it to establish a gap of 3 mm to 6 mm When the electrode contacts the plate, current begins to flow, and as it is retracted, a small spark maintains the current across the gap This spark ionizes the air, allowing the current to continue flowing even with a larger gap The resulting heat is sufficient to melt the materials being welded.
The parent plate can be joined through the melting of the electrode's end, where the resulting molten metal is transferred in small globules across the arc into the molten pool.
To initiate the electric arc in Shielded Metal Arc Welding (SMAW), the electrode lightly touches the workpiece before being pulled back, which melts both the workpiece and the electrode, creating a weld pool As the electrode melts, the disintegrating flux generates shielding gases that protect the weld area from atmospheric contamination and produces molten slag that covers the filler metal This slag floats to the surface of the weld pool, providing additional protection as it solidifies, but must be chipped away to reveal the finished weld The welder frequently needs to replace the electrode stub during the process, which, along with removing slag, limits the time spent on actual welding, leading to an operator factor of about 25%, making SMAW one of the less efficient welding methods.
The choice of welding technique is influenced by factors such as the electrode type, workpiece composition, and joint position, which also affect welding speed Flat welds are the easiest to perform, requiring minimal skill and allowing for the use of fast-melting electrodes that solidify slowly, resulting in higher welding speeds In contrast, sloped, vertical, or overhead welding demands greater skill and typically requires faster-solidifying electrodes to prevent molten metal from spilling out, which can slow down the welding process due to the electrodes melting more slowly.
Common quality issues in Shielded Metal Arc Welding (SMAW) include weld spatter, porosity, poor fusion, shallow penetration, and cracking Weld spatter, although not compromising weld integrity, affects appearance and increases cleaning costs, often caused by high current, long arcs, or arc blow Arc blow can also lead to porosity, which is exacerbated by joint contamination and high welding speeds, posing a significant risk to weld strength Poor fusion, visible and caused by low current or contaminated surfaces, further weakens the weld Shallow penetration can be improved by adjusting welding speed, increasing current, or using smaller electrodes Cracking can result from high carbon, alloy, or sulfur content in the base material, especially without low-hydrogen electrodes or preheating Additionally, excessive restraint of workpieces introduces residual stresses, increasing the likelihood of cracking during cooling.
SMAW welding poses significant health and safety risks if proper precautions are not followed The open electric arc can cause burns, which can be mitigated by wearing heavy leather gloves and long-sleeve jackets Welders are also at risk of arc eye, a condition caused by ultraviolet light exposure that can damage the eyes, thus requiring the use of welding helmets with dark face plates, including advanced models that self-darken in response to UV light To protect bystanders in industrial settings, transparent welding curtains made from polyvinyl chloride are used to shield against UV exposure, although they should not replace the filter glass in helmets Furthermore, the welding process generates harmful gases and particulate matter, with smaller particles posing a greater toxicity risk Inadequate ventilation can lead to the accumulation of dangerous gases like carbon dioxide and ozone, prompting the use of modern welding masks equipped with electric fans to help disperse these harmful fumes.
Shielded metal arc welding is a widely used welding process, representing over half of all welding activities in some countries Its versatility and simplicity make it particularly favored in maintenance, repair, steel structure construction, and industrial fabrication Although its popularity has declined in recent years due to the rise of flux-cored arc welding and gas metal arc welding in various sectors, its low equipment cost and broad applicability ensure it will continue to be a preferred choice among amateurs and small businesses where specialized welding methods are not cost-effective.
SMAW is a versatile welding technique primarily utilized for carbon steel, low and high alloy steel, stainless steel, cast iron, and ductile iron Although it is less common for nonferrous materials, it can effectively weld nickel, copper, and their alloys, and in rare instances, aluminum The minimum thickness for welding typically does not fall below 0.05 inches (1.5 mm), largely depending on the welder's skill, while there is no maximum thickness limit; with appropriate joint preparation and multiple passes, virtually any thickness can be welded Additionally, SMAW allows for welding in any position, contingent on the electrode choice and the welder's expertise.
2.What kind of the heat source is it in MMA welding?
3.How is the arc for med?
4.What are the advantages of the flux?
5.Is the slag good for the weld?
6.What determine the welding speech?
7.Which welding position requires the least operator skill?
8.Can arc blow cause porosity in the weld?
9.How can shallow penetration be addressed?
10 What kind of contents in the base material can lead to cracking?
11 Why is SMAW welding welding said to be dangerous and unhealthy?
12 What kinds of steel and iron is often used with SMAW?