Surfacing welding manufacturing (vertical mill surfacing points)!

The greatest risk of this method of manufacturing abrasion-resistant parts is the peeling of the wear-resistant layer and the fracture of the workpiece. The first refers to the peeling off wear-resistant layer and the base metal cast steel stripping; the second is between the wear-resistant layer peeling. Generally, the thicker the wear-resisting layer is, the higher the possibility is. In order to reduce the risk of spalling, strict control is required in the thickness of the overlay layer, the selection of the welding wire, the construction process and the construction operation.

 First, the welding failure and risk analysis Surfacing failure forms include fatigue, wear, flaking and fracture, it includes the following reasons:

1, roller running period is too long cause the roll surface hardening and the formation of micro-cracks after the expansion;

2, casting defects: such as cracks, pores, slag, shrinkage and so on in the operation and welding process will continue to expand, especially in the stress concentration parts prone to crack, the occurrence of local out of pieces, off or broken phenomenon;

3, fracture failure and casting in the casting process and the heat treatment process has a direct relationship between the defects, such as residual thermal stress;

4, the roller in the course of the operation of the local poor contact will make the grinding roller in the gap with a stress concentration (from the roller structure shape, roller and the hub of the cylinder with the surface is due to roller and wheel hub Two pairs of the surface with the existence of processing errors, grinding roller and hub assembly is difficult to ensure that the column at the same time contact, this local contact will make the roller in the gap with the gap to produce stress concentration);

5, vertical mill production process not only exist when the vibration of large particles of material, but also in the role of hot gas into the grinding roller in the open and shut down by the role of temperature changes, the roller in the thermal stress, heat treatment residual Stress and grinding force, easy to have defects in the casting and grinding wheel and hub with a gap in the fracture site. The fracture extending from the inner side to the outer side of the grinding roll;

6, roller preload is too large to install one of the reasons roller failure;

7, the choice of surfacing materials and surfacing welding process caused by improper workpiece fracture.
Second, to avoid and reduce the risk of surfacing the necessary measures Surfacing the roll there is the use of age that is the problem of life. To roller long life, need two aspects, one is the proper use of the user, on the other hand is the welding quality assurance.

1, in terms of use

1), the installation process, as far as possible through the trial assembly so that the roller sleeve and the hub can be in contact with the cylinder at the same time, when there is poor contact should be good repair scraping guarantee contact.

2), in the open and stop grinding, in strict accordance with technical specifications to control the cooling time and grinding time.

3), in daily production, when the grinding of the finished product moisture ≤ 0.8% and does not affect the kiln mill system air flow balance, the most into the grinding gas temperature.

4), control into the grinding material ratio and size, try to avoid vertical mill production in the strong vibration.

5), the development of roller into and out of the mechanism to determine a reasonable replacement cycle and the number of on-line surfacing.

2, in the welding process:

1), before the welding of the base metal ultrasonic testing and detection of wear and tear to remove defective parts; first of all before welding on the workpiece to check the wear and tear, the test results directly determine the weldability of the workpiece, which is welding Before the detection, wear detection, testing is the status of the roller itself can have a clear diagnosis. Before and after welding on all items tested, such as hardness testing, color testing, magnetic detection, ultrasonic testing and so on. Coloring the surface of the workpiece with a colorant before welding, and inspecting the roller / liner for cracks, casting defects, local wear and other abnormalities using an ultrasonic inspection method. If casting defects or local wear phenomenon, the first defect or local wear and tear repair. If some of the workpiece itself has a relatively large defects, such as penetrating cracks or local wear, etc., the risk of welding remanufacturing is relatively large, it should consider whether it is worth repairing. The characteristics of the base metal itself will directly determine the use of wear-resistant parts and life characteristics, such as the toughness of base metal, base metal itself, the existence of cracks, the parent material and welding materials fusion and so on.

2), according to the base metal composition selection of appropriate welding material;

3), the development of scientific and reasonable welding process and strictly regulate the operating procedures;

4), control the level of arc welding arc and arc: the height of the device through its own track to automatically achieve a serious local wear parts of the welding repair;

5), surfacing quality inspection and assurance:

Wear - resistant parts of the old base material composition, surface hardness, structure size, wear - type line, the situation before welding record detection;

Quality certificate of surfacing material;

 Wear-resistant parts welding process assessment report, welding process measures or operating instructions;

 Wear - resistant parts after welding re - manufacture of the appearance of inspection and finished size records;

 Welding layer hardness test, nondestructive testing and other reports.

 Wear-resistant parts factory, should be based on the need to surfacing antirust paint.

 Good wear-resistant surfacing should be stored in dry, flat, solid venue, the venue must have a reliable measure of rain.

 The welding seam of the factory should be accompanied by a certificate, the certificate must indicate the following: the name of welding parts, job number, weight and quantity;

Surfacing technical documentation should be prepared and filed in time.

Third, the implementation of welding process

Construction → Cleaning → Weighing → Dyeing → Wear measurement → Welded on the first machine → testing the first → firmness welding the first side, the detection of solid → → to the original size of welding → under the machine, the refurbishment , Anti-rust treatment → false installation, paint and then check the size → weighing, packaging.
Fourth, the specific implementation steps

1, construction preparation

1), to develop wear-resistant welding process, welding process design should include: welding process parameters, including welding diameter, weld width, welding speed, welding volume, welding current, arc voltage, Welding wire out of the length and inclination, hardness, welding thickness deviation, round wear parts after welding oval, allow the depth and length of cracks, edge welding residual temperature and workpiece temperature.

2), welding process requirements

 2.1 The formation of uniform turtle cracks and prevent the surfacing layer peeling.

2.2 The use of low-temperature cold welding, welding process to strictly control the layer temperature.

2.3 to prevent the hardness of the surfacing layer does not meet the requirements.

2.4 to prevent deformation of surfacing parts.

3), wear-resistant welding process control Reasonable surfacing welding repair process is to achieve vertical grinding roller / disc surfacing repair key. According to the different wear conditions of roller / disc and the actual working condition, it is reasonable to design and select the wear-resistant surfacing technology in order to achieve the best surfacing repair effect.

3.1 to do partial surfacing, using one-way welding method to fill the flat roller pit, the patch should have the appropriate transverse cracks to release the welding stress;

3.2 by automatic welding method to the required size;

3.3 in the whole welding process, the weld layer temperature should be strictly controlled;

3.4 Surfacing Note: Avoid excessive dilution; hard surface layer must be established transverse crack, in order to release the welding stress; welding layer should not be flame cutting and machining; for the resulting welding gas should be promptly cleaned with arc gas flat formation.

2, the base metal before the penetration of the flaw detection (or magnetic detection), ultrasonic testing methods such as the matrix, and eliminate the casting defective parts (when there is wear-resistant parts of the old product through the crack, the local matrix wear, If the thickness of the substrate is too thin and so on, which may lead to the failure of the whole body, it is inadvisable to carry out welding and remanufacturing.

3, roller repair surface treatment before