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- Standards for welding work
- Components of standardization of welding work.
- Standard time for welding work as the basis of the labor process
- Quality control of welding work Quality control of welded parts
- Visual and mechanical quality control of welded joints
How is the main time for gas welding determined?
The main time of gas welding is for 1 linear line. m of seam is determined by the formula To=CF min, ... m of seam, min; C-time of deposition of 1 cm3 of metal (Table.
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Checking the quality of received connections
SNiP regulates the quality control of welded joints in sufficient detail. Control can be carried out by the welder himself or by workers specially designated for this. Another option is to seek help from special laboratories whose activities include carrying out such operations.
Before welding work begins, it is necessary to check whether the qualifications of the welders to whom they are entrusted correspond to the complexity of the task. The welder must present a work permit to perform specific welding work. If the purpose of the welding joint is of increased importance, then preliminary testing can be carried out on a sample of the same material and the same dimensions.
Before starting, it is also necessary to inspect the parts to be joined using the welding process. They must be made of material for which there are certification documents. Before starting welding, a thorough inspection must be carried out to identify defects on the parts to be welded. What the quality of parts should be is also indicated in regulatory documents, including SNiP.
Production control of welding work includes the following stages:
- Incoming control . It applies to process documentation, the design of joints to be welded, equipment used, as well as auxiliary devices and tools.
- Operational control . Welding processes and technological operations are subject to it. It is necessary to check the correctness of their implementation. Operational control also includes checking the use of equipment and compliance with safety regulations.
- Acceptance control . The quality of the welds and connections made is subject to examination.
When performing input and operational types of control, it is necessary to follow the instructions set out in the regulatory document SNiP 3.01-85. For each type of control, technical standards for welding work are applied.
Quality control of welding work begins with a visual inspection. It allows you to identify all external defects visible to the naked eye. SNiP allows the use of a high-magnification magnifying glass for visual inspection. Rejecting connections whose external defects cannot be corrected or would not be economically feasible saves time and money.
According to the requirement of SNiP, all welds without exception must be subjected to visual inspection. Templates and calipers are used to measure the defect. Before starting a visual inspection, it is necessary to prepare the surface by cleaning it.
The second popular method is capillary. The advantage of this method is its versatility. SNiP allows its use to identify defects such as cracks of various sizes and pores, as well as burns and lack of penetration. This method uses a special penetrating liquid; no additional equipment is required. A combination of the capillary method with others is allowed. Special solutions or filter suspensions can be used as a penetrating liquid.
The capillary method is divided into several varieties depending on the method of obtaining information. Before penetrant testing can begin, the area being tested must be thoroughly cleaned. Various solvents are used for it. The control itself is carried out by applying special indicators to the surface of the welded joint.
The tightness test is carried out by monitoring the tightness. A properly executed connection should not allow passage of either liquid or gaseous substances. If there are through-through defects, this requirement is not met. Requirements for welds of metal structures limit the size of such a defect according to the tolerances specified in the documentation.
A common method for testing welded structures is magnetic flaw detection. The method can only be used to control ferromagnetic parts. Magnetic flaw detection helps to detect small cracks inside the weld, as well as foreign inclusions.
An information method is ultrasonic testing of welded joints of metal structures. It is suitable for testing parts made of various types of metals. The method is based on the fact that when an ultrasonic wave hits a defective area, it distorts. Ultrasonic testing requires special equipment.
The ultrasonic method can detect the presence of many different defects, ranging from pores and cracks to changes in geometric dimensions. Radiation monitoring is an informative but not safe method. It is carried out by illuminating the welded joint with X-rays and gamma rays. The equipment required to implement this method is an X-ray machine, which contains an emitter that generates X-rays.
SNiP regulates that the choice of X-ray machine depends on the thickness of the welded parts. There are also special requirements for the film used in the X-ray machine. Radiographic testing, in addition to an X-ray machine, involves the use of a flaw meter, which is a metal plate with grooves.
All mechanical and metallographic control methods are destructive types.
Components of standardization of welding work.
Standards for welding work in electric arc welding include such components as time, amount of work, output, etc.
The time taken to produce a particular unit becomes the time standard when performing electric arc welding. One kilogram of metal deposited during the welding procedure, one meter of welding unit, as well as one part made during welding will be the amount of work.
Time standards are measured in minutes per meter. The production standard refers to the entire range of work completed within a certain time. This output is measured by the length of the weld (in meters) that was completed per working hour or shift.
Electricity consumption is also a very important unit, both from a technical and economic point of view. The units of measurement for electricity consumption are kilowatts per hour per kilogram of metal melted during the welding procedure.
How many joints should a welder weld per day?
Assessing the effectiveness of a welder’s production activities and calculating his remuneration is carried out taking into account the time standards for welding work.
The time indicator depends on several factors: the qualifications of the performer, the group of material being welded, the type of seam joint, working conditions, equipment.
When assessing the rate of time spent, all types of activities of the welder should be taken into account. The work can be roughly divided into several stages:
- The main procedures include procurement, pre-processing, assembly, welding itself and final finishing necessary to obtain a complete product;
- auxiliary operations consist of monitoring the condition of the received product and delivering it to the intended place;
- Additional time is required to maintain welding and organize conditions for proper storage of materials and devices.
Time standards for carrying out the main set of welding work take into account the time spent on preparing all the necessary materials and parts; bringing equipment and auxiliaries into working condition.
An important factor for calculating time standards is the period during which the work zone is initiated. An example would be arc burning time.
The main types of welding work are accompanied by mandatory auxiliary activities. You need to change the electrode, carefully inspect the seam, and prepare the edge if necessary.
All main and auxiliary procedures constitute operational welding time. It is impossible to postpone them without compromising the result.
Quantitative calculation of the rate of time spent determines the welding speed, which should ensure a high-quality seam. To a predominant extent, it depends on two values: the thickness of the product and the weld seam. You need to work so that the liquid melt does not overfill the working bath, does not form sagging, and smoothly passes to the main part of the parts.
Exceeding or decreasing the speed leads to a sharp deterioration in the quality of work, changing the welding time. At optimal speed, the seam is deep enough, but not very wide.
This guarantees compliance with quality standards. For manual arc welding, the best results are usually obtained by welding work carried out at a speed of 30-40 m/hour.
Standard values may vary depending on the specifics of the material. With semi-automatic welding, speeds are often higher. This is understandable and explainable by the specifics of the equipment used.
A welder, in accordance with his qualifications, has to work with a variety of materials. This significantly affects the standard welding time.
It is customary to distinguish several main groups, differing in the content of chemical components and purpose. For example, group M01 includes structural steel alloys with a carbon and low-alloy composition. The yield strength of these materials does not exceed 360 MP.
As the value of the number in the marking increases, the characteristics of the alloys improve. Thus, class M07 includes reinforcing steels intended for the manufacture of reinforced concrete structures. When calculating time standards for welding work, the quality of materials is of fundamental importance.
When making calculations, a number of standard indicators are used that take into account the specifics of welding, the qualifications of the performer, the characteristics of the chemical composition and shape of the parts. In its simplified form, the formula is a fraction.
The numerator contains the length of the seam joint, the denominator is the normalized speed for a given production situation. The resulting value must be multiplied by a factor of 0.35, thus obtaining the time standard for visually assessing the quality of the seam.
To take into account the duration of stripping a seam, you need to multiply its length by a factor of 0.6. The total indicator displays the total amount of time for the main part of the welding work.
Preparation requires 5% of the time from the obtained value. We calculate this indicator and add it to the previous number. After that, you should take into account the need for the worker to rest, which should be at least 10% of the time spent on welding.
The total indicator is the standard time spent on carrying out specific welding work on the object in question.
It should be taken into account that the standard indicator of the speed of welding work is significantly influenced by the size of the cross-sectional area of the part, the current strength, and the quantitative characteristics of the electrodes and melt in the working area.
Calculation of time standards for welding work can only be carried out by experienced specialists in the field of labor standards with knowledge in this industry.
Welder is a prestigious profession. They get paid better than many others, because a high-quality welder is worth his weight in gold. But knowing how to cook using conventional methods is not a difficult task.
As practice shows, after several attempts, even the most ordinary person can somehow weld one metal workpiece to another.
That’s why people learn this profession, that’s why there is such a thing as the ranks of welders.
Before moving on to analyzing the categories of welders, it is necessary to understand the categories.
Specifications
Standardization of assembly and welding work can be carried out competently only if technical documentation for a specific product is available. One of the most important documents is the technical specifications for the manufacture of a welded structure. This document contains a description of all stages of the welding process, requirements for them and methods of implementation. Technical conditions are carried out on the basis of current regulatory documents for this type of activity, in particular, they must be drawn up on the basis of the requirements and recommendations of SNiP.
Technical specifications are drawn up based on available drawings. They must indicate special conditions for performing the welding process, for example, increased mechanical loads.
Requirements for welds
It is also advisable for the welder to know the requirements for welds of metal structures. This will contribute to proper quality control and adequate assessment of your work.
Welding metal structures or welding pipelines implies the absolute strength and reliability of the welds. This can only be achieved if the requirements for the mechanical properties of the joints are fully met. Based on GOSTs and rules, we have identified the following basic properties of the seam that must be observed in order to obtain a high-quality connection:
- The relative elongation of the weld metal should not be less than 15-16%.
- Impact strength must be at a high level. To find out this parameter, you need to conduct a test: check the reaction of the seam at the average daily temperature, and the test must be carried out for a week at the lowest temperature in your region. The minimum value of impact strength is 29 J/sq.cm.
- The tensile strength of the weld should be similar to that of the metal used for welding. A lower resistance value is not allowed.
- The hardness of the metal should be 350 HV for welded structural elements belonging to group 1, and 400 HV for welded elements of all other structures. These rules are regulated by SNiP II-23.
When welding metal structures, it is extremely important to pay attention to the quality of the seam itself. Previously, we talked about how the quality control of welding joints is carried out, now we will talk about the classification of seams based on their quality. So, seams come in three categories:
- First category. Best quality. This category may include any type of seams that have special requirements for durability and reliability. Seams of the first category must withstand enormous loads and ensure reliable connection of complex metal structures, including industrial ones. Seams of the first category are used to weld metal frames of buildings and the hull of ships. Also in the first category are seams designed for long-term use in harsh climatic conditions. For example, in the Far North.
- Second category. Medium quality. This is the most common category and includes any type of tear-resistant seam. In general, most compounds can be classified into this category. A striking example is the seams used to weld car bodies. Such seams can withstand relatively large loads, but are not designed for use in harsh conditions.
- Third category. Below the average. Seams of this category are not necessarily the worst in quality, but they definitely cannot be applied to critical structures. But you can weld auxiliary metal structures, saving time and effort.
Standard time for welding work as the basis of the labor process
Welding generators are an indispensable tool for performing high-quality manual welding with stick electrodes. The welding generator is designed in such a way that during operation the strength of the welding current remains practically unchanged, that is, it does not depend on the length of the welding arc, which can change quite slowly, depending on the speed of the welder’s hand. Only this condition will allow the arc to be constantly in a state of combustion.
Welding work requires a well-equipped workplace. A wooden tabletop is clearly not suitable for such work. In this article we will tell you how you can assemble a steel welding table with your own hands with little time and money.
This article will focus on occupational health and safety during the welding process. Let us dwell in detail on traumatic situations that can be avoided by following safety rules. We will also tell you about the labor protection rules for welders.
