Current situation analysis of casting industry

I. analysis of the current situation of foundry industry (ratio of yield patching)

At present, the production scale of China's casting industry and the production of castings are all in the forefront of the world. The strong industrial base provides a large number of castings (rough and spare parts) for many industries.

In recent years, China's foundry industry has entered into ChangDian, yield more big, all kinds of casting power in the world, and at the same time our country casting export growth faster, only 1 - steel, cast iron parts in China in March this year production reached 2469140 tons, 1040613 tons, up 13.32% from a year earlier, 12.54%. Export products are also made from simple components to higher requirements of complex castings. But compared with the great powers such as America, Japan, Germany and France, there is still a considerable gap.

The main reason is that the casting in our country is famous for 'old' 'big' 'black' and 'thick', mainly because of the high rate of waste products in the casting industry in China. The reject rate of ordinary cast iron parts in China is about 10%, complex pieces, high-grade pieces are around 10% to 15%, and aluminum alloy die casting is in the range of 8% to 10%. At the same time, the defects mainly focus on the surface of the casting or the internal air hole, the sand eye, etc. About 80 percent of these defects can be saved through repair. For many reasons, lead to defects in the process arrangement, selection of materials, casting mould design and fabrication, such as casting process, if not scientific and rigorous design and execution, will lead to the emergence of the rejection rate and improve.

With the development of the world economy, China has become a casting power, and casting production must take the sustainable development path of high quality, high efficiency, low consumption and clean. The basic method is: castings are developed from low value-added products to medium and high-end castings. This requirement must raise the technical level of the whole casting, but the casting technology level is a systematic project, which is subject to the actual situation, and it is difficult to get a significant improvement in the short term. Top priority is to reduce the waste product rate of castings, thus casting repair efficiency has been more and more be enterprise value, even if the technology power is very strong foreign enterprises and large state-owned enterprises have also adopt the way of casting repair to make up for the inadequacy of the existing foundry technology. Companies often take different approaches to the rescue of defective castings.

Ii. Repair situation and equipment analysis

1. Casting glue:

It is an instinctive choice for enterprises to repair castings. The main features are simple, convenient, low price and low demand for employees. However, this method is only suitable for rough casting, and the general patch can not be processed for further processing, and the strength hardness is very low. Such a process is suitable for simple and coarse casting, or for low-value castings. With the development of foundry industry, foundry glue is becoming more and more unsuitable for customers' demands.

2. Welding:

Almost all foundry manufacturers have chosen to solve the casting defects encountered in production. The welding repair of the casting is that the metal filling material is usually matched with the casting material, thus achieving the basic mechanical performance standard required by the mother. This requires a variety of complementary methods; The welding method is simple; The welding efficiency is high, the welding cost is low, the welding supplement is small to the environmental pollution, and the subsequent treatment after welding is simple, which can be accepted and trusted by the foundry manufacturer. At present, there are many kinds of welder for casting welding, and there are some of the following:

2.1 welding machine

Electric welding machine is indispensable for foundry equipment, it is to use when the instantaneous short circuit arc ignition electrode poles, using the arc to melt welding electrode and welding material, then reach the purpose of make them combined with cooling. It is the most traditional welding method, usually used for cast iron, cast steel welding, or some traditional welding and welding.

Advantages: suitable for work in a dry environment, don't need too many requirements, a relatively small volume, simple operation, easy to use, fast, weld after welding, suitable for the welding repair welding of large area. It can instantly connect the same metal material (also can connect the foreign metal to different metals, only the welding method is different) for a permanent connection. After the weld is treated with heat treatment, it is the same strength as the mother material, and the sealing is very good.

Faults: electric welding machine in the process of using welding machine will produce a magnetic field around, arc combustion would produce radiation into the surrounding, arc of infrared, ultraviolet light, such as and harmful material such as metal steam and smoke, so operation must do enough protective measures, and need special welders. It is not suitable for welding welding of high carbon steel. Due to the process of weld metal crystallization and segregation and oxidation, the internal stress is easy to crack after welding, resulting in hot cracks and cold cracks. It is easy to produce secondary defects such as stomata and slag. Solder joints have high hardness and generally need annealing heat treatment to meet the processing requirements. This determines that the welder can only repair some of the rougher castings. Even if the precision casting is repaired, it needs to be preheated. After welding, annealing is required and the welding is complicated. This requires more advanced welding equipment to make up for its deficiencies.

2.2. Argon arc welding:

Argon arc welding is also known as argon arc welding. It is to prevent the oxidation of welding zone by shielding the air from the arc of the arc welding.

Precision casting (alloy steel, stainless steel casting), aluminum alloy die casting parts adopt argon arc welding machine. Some molds manufacture and repair the factory, also use this welder to fix the mould defect.

Advantages: high efficiency and high accuracy. There are many kinds of welding wire, the most widely used in stainless steel and aluminum alloy products. Can be used for welding, high strength.

Disadvantages: the argon arc welding is large because of the thermal influence region, because D has a large impact on the casting, and the edges of the molten pool are marked. Hard points are made for welding steel. Thermal distortion can be easily produced when welding or lining is made by heat. The operation technique demands high. After the workpiece is repaired, it often causes deformation, hardness reduction, sand eye, local annealing, cracking, pinhole, abrasion, scratch, biting edge, or insufficient joint force and internal stress injury. In particular, the repair process of fine casting defects is prominent on the surface. Argon arc welding and welding rod arc welding compared to human body harm degree, argon arc welding current density is big, the light is strong, its arc ultraviolet (uv) radiation, about 5 ~ 30 times that of the ordinary, welding, infrared is about 1 ~ 1.5 times of the welding rod arc welding, the welding when the ozone content is higher, therefore, to choose better air circulation, local construction as far as possible, otherwise there is a lot of harm to the body. This requires that the argon arc welding needs to be in a specialized place, which requires special personnel operation, which greatly reduces its flexibility.

3. Cold welding repair

Cold welder: it can be released at an instant (ms-level) to a minimum range (<1 square millimeter) to make the material completely fused to the workpiece. In the process of welding, the workpiece produces a small amount of heat and the workpiece is generally in a normal temperature state, so it can avoid the disadvantages such as deformation, crack and discoloration of traditional welding. After several years of development, the application direction and technology of welder have been greatly developed, and it has a large share in the repair market.

According to the product classification of cold welder: patch machine and conventional electric spark surfacing repair machine.

1. Patch machine

On the principle of instantaneous high frequency discharge welding sheet (steel sheet, powder, solder powder or processed waste cutting), (0.05-0.20 mm) by high-frequency discharge paste to the workpiece surface or fill to the defects such as sand holes, each maximum equivalent and welding paste thickness slice thickness, welding quality depends on whether discharge uniformity. Suitable for workpiece wear, machining super-poor repair. The advantages are that after the repair, the casting color difference is small, basically does not produce the internal stress, no deformation bite, the repair after welding is small, can be processed directly.

Disadvantages: the welding speed is slow, usually 2mm hole needs 3-5 minutes, not suitable for large-scale repair; After repair, the hardness is low, usually only around the HB150, and the high hardness of the casting can only hope to sigh; Low degree of conjunctedness, because the material is attached to the workpiece, and the lathe milling machine is easy to fall off. Bright and clean degree is low, after welding for processing after the finish requirement of casting half-heartedly, fill material, due to its often use copper bar contact appears unavoidably copper scrap or small pores of pitting, can repair some casting processing requirement is too high

2. Conventional electric spark surfacing repair machine

Using spark instantaneous high frequency discharge principle, the nickel - based welding material or special welding material is immediately applied to the surface of the workpiece, and the welding material and the workpiece are fused together in metallurgy mode. The surface of the workpiece produces little heat during the whole process of welding. The welding gun USES the rotating electrode, the diameter of the wire is different from 1.6-3.0mm. Suitable for casting defect repair. The machine can be applied to the power and discharge frequency setting. Steel, copper, aluminum and other metals can be repaired.

Advantages: easy installation, easy operation, general personnel training can be operated. High strength weld repairs, welding repair parts without annealing, no crack, no deformation, internal stress, solder joint does not produce processing hard point, relative to the SMT machine repair speed is faster, to repair the accuracy is higher, and can through X-ray flaw detection, penetration, such as tensile test. Has been accepted and used by many foundry manufacturers. In addition, there is also some use value in mold repair.

Faults: slow, 2mm cast iron takes about 3 minutes. In the case of less welding materials, the iron parts can only be used for the high welding cost of nickel based welding materials (300 / kg), and the utilization rate of welding materials can only reach 80%. Color difference is relatively large, each low, due to its principle of high frequency discharge, also is a granular surfacing, combining with the relative to argon arc welding is low, the non-ferrous metal iron pieces of poor compactness. The smooth finish is not high, the casting cannot meet the requirement for high and clean. Moreover because of the traditional design principles of cold welding machine, power is in commonly 2000 w, the internal electronic components are exposed, in this environment, the foundry machine often out of order, especially the electrode gun (gas-electric separate, easy to damage), is a waste of energy and is not suitable for large-scale repair request casting manufacturer.

3. Esd-05 high efficiency, one-engine multi-use spark surfacing repair machine

ESD - 05 adopt unique chopping soft switch technology, precise output control in addition to the traditional cold welding machine is easy to operate, the normal temperature welding repair, hand can touch generating internal stress after welding repair, can be directly to car milling planer milling characteristics of various kinds of processing. Its uniqueness:

3.1, output, control precision, the internal integration design, electronic components enclosed layout, unique board structure design, so to avoid the traditional edm welding repair machine common fault, electrode gun by gas thermal electrical integration design, greatly reduces the failure rate. And combines the principle of WS welding characteristics, the use of half welding (ion conversion plus' particles' transformation), so the ESD - 05 high-energy spark surfacing welding repair machine is only the power of 600 w, but the weld speed, effect is traditional edm welding repair machine, 2000 w for several times. It is necessary to point out that the electric spark electric welding repair machine is not the traditional welder, the speed and effect are not determined by power, the key is the optimization design of the internal system.

3.2, welding materials applicability is wide and ordinary electrode remove coated directly use, such as 308208303506, non-ferrous metal materials article argon arc welding electrode or even his ontology of electrode can be used. This greatly reduces the cost and manpower cost of casting manufacturers.

3.3, the welding speed is fast, the aluminum alloy of 2mm only needs 10s, 2mm gray iron only takes 1 minute. Due to ESD - 05 USES a single point energy output is high, the weld material of every single point in the molten state to the substrate, forming metallurgical combination, the combination of the extremely high spent (half melting welding properties), especially to overcome the traditional edm problem of poor compactness after weld repairs, which greatly improve the efficiency of the casting factory repair.

3.4. The problem of low welding of high content magnesium alloy and copper alloy is generally considered to be unsoldable. Because of the instantaneous high energy output of esd-05, the welding of high conductivity metal such as copper and aluminum has been effectively solved, which has overcome the shortcomings of ordinary point spark surfacing.

3.5, ductile iron, grey iron weld repairs after phosphating of off color problem has always been a difficult problem, due to ESD - 05 can use a variety of welding materials, we have found a welding material, can make the grey iron ball after weld repairs, iron phosphating without off color or color difference is very small. It can also be used to make the ash iron welding after the grinding machine or milling machine with no color difference or color difference, and can also use oil stone polishing.

3.6. Disadvantages: the efficiency is still less than the welding machine, argon arc welding machine.

Esd-05 efficient, multi-purpose spark surfacing repair machine with its outstanding advantages makes people prefer to choose.