Valve manufacturing process features

At first glance, there are few valve parts, simple structure and general precision. It is a simple part in the machinery industry, but the core sealing part of the valve is required to be particularly high. The valve manufacturing process is complicated and the technical difficulty is also great. Which process features do we need to pay attention to?

1. Manufacturing materials

Due to the variety of valve specifications, it is used in various fields of the national economy. Its use occasions vary widely, such as high temperature and high pressure, cryogenic cryogenic, flammable and explosive, highly toxic, corrosive media and other working conditions, the valve material proposed Demanding requirements.

In addition to cast iron, carbon steel, and alloy structural steel, CrNi stainless steel, CrMoAl nitrided steel, CrMoV heat resistant steel, CrMnN acid resistant steel, precipitation hardened steel, duplex stainless steel, low temperature steel, titanium alloy, Monel alloy are also widely used. , Inconel, Hastelloy, and G0CrW carbide. The casting, welding, and processing properties of these high-alloyed materials are very poor, causing great difficulties in the manufacturing process. In addition, most of these materials are high-alloy, high-strength, high-hardness precious materials, and there are many difficulties in material selection, material preparation, and procurement. Some materials are difficult to purchase due to their small usage.

2. Structure of the cast blank

Most of the valve blanks use thin shell castings with complex structures. Not only do they require a good appearance quality, but also have a dense internal quality and a good metallurgical structure. They cannot have defects such as pores, shrinkage holes, sand inclusions, and cracks. . Therefore, the casting process is complicated and the heat treatment technology is difficult. In the machinery industry, the casting of the pressure-bearing shell casting blanks of the valve is far more complicated and difficult than the casting of other mechanical components.

3. Machining process

Since most of the high-strength, high-hardness, and high-corrosion materials have poor cutting performance, such as high-alloyed stainless steels and acid-resistant steels have drawbacks such as high toughness, high strength, poor heat dissipation, high chip viscosities, and strong tendency to work hardening. Difficult to achieve the required dimensional accuracy and finish, to bring certain difficulties to the machining of tools, processes and equipment. In addition, the valve sealing surface in the processing accuracy, matching angle, finish and mating seals are also very high requirements, to bring great difficulties to the machining.

4. Process Arrangement of Valve Parts

The number of main parts of the valve is small, the structure is relatively simple, the machining accuracy of most of the dimensions is not high, and the exterior is rough, which gives the impression of being a simple machine. In fact, the heart seal of the valve can be extremely precise. Its sealing surface has a high degree of "third degree" (flatness, finish, hardness), and the degree of fit of the sealing pair consisting of the two sealing surfaces must reach zero to zero. In order to meet the zero leakage of the airtight test. This kind of precise zero-to-zero requirement for the heart area with a rough reference is the biggest technical difficulty in valve machining.

5. Valve test and inspection

The valve is an important opening and closing and regulating element of the pressure pipeline, and the operating conditions of the pressure pipeline are very different, high temperature and high pressure, cryogenic cryogenic, flammable and explosive, highly toxic corrosion. However, the valve manufacturing test and inspection conditions are unlikely to meet the same requirements for working conditions, and the international and domestic standards for testing of various valves are tested with gas or water as a medium under conditions close to normal temperature. There is a fundamental risk that this is a valve product that has passed the normal factory test. Under harsh practical conditions, it may be difficult to meet the requirements due to material selection, casting quality, and seal failure. Quality accident. No wonder some of the old valve experts have worked for a lifetime, the older they are, the more cautious they are, the more worried they are.

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What looks like a simple valve is actually not that easy to manufacture?

So, how exactly does the valve be manufactured step by step...

Valve manufacturing process

The first step: valve body manufacturing

Valve body (casting, sealing surfacing)

Procurement of castings (according to the standard) Incoming inspection (according to standards) Slurry welder Ultrasonic inspection (according to drawings) Surfacing and post-weld heat treatment Finishing Grinding sealing surfaces Sealing surface hardness testing, coloring inspection.

Step 2: Valve Internals Manufacturing Process

A, need to surfacing the internal surface of the sealing surface such as flaps, valve seats, etc.

Raw material procurement (according to standards) Incoming inspection (according to standards) Production of blanks (round bars or forgings, according to the drawing process requirements) Rough machining ultrasonic flaw detection surface (when drawings are required) Roughing surfacing welders Surfacing and post-weld heat treatment Finishing Grinding sealing surface sealing surface hardness test, color detection.

B, valve stem

Raw material purchase (according to standard) Incoming inspection (according to standard) Blank (round steel or forging, according to the drawing process requirements) Roughing surfacing welding and post-weld heat treatment Finishing All parts grinding External cylindrical stem Surface treatment (nitrogen Finishing, quenching, electroless plating) Final treatment (polishing, grinding, etc.) Grinding sealing surface sealing surface hardness test, color inspection.

C, do not need to weld the internal surface of the sealing surface, etc.

Raw material procurement (according to standards) Incoming inspection (according to standards) Production of blanks (round steel or forgings, according to the requirements of the drawings) Roughing of the ultrasonic flaw detection surface (at the time of drawing request) Finishing of various parts.

Step 3: Fastener Manufacturing

Fastener Manufacturing Standard.

Raw material procurement (according to standards) Incoming inspection (according to standards) Blanks (round bars or forgings, according to the drawing process requirements) are prepared and sampled for necessary inspections. Roughing Finishing Spectral inspection.

Step 4: Final assembly

Receiving parts Cleaning, cleaning Coarse assembly (according to drawing) Hydraulic pressure test (according to drawing, process) After passing, dismantle, wipe clean Final assembly and electrical installation or actuator adjustment (for electric valve) Paint packaging Shipping.

Step 5: Product Production and Inspection Process

1, the company purchased a variety of specifications of raw materials.

2. Perform the material test on the raw materials with an optical spectrum analyzer and print out the raw material test report for backup.

3, use cutting machine for raw material cutting.

4. Inspectors inspect the cutting diameter and length of raw materials.

5, forging workshop for raw materials forging forming processing.

6, inspection personnel on the formation of various sizes of blank inspection.

7. The worker removes rough edges.

8. The sand throwing workers perform surface sandblasting on the blanks.

9. Inspectors perform surface treatment inspection after sandblasting.

10. Workers perform rough machining.

11, valve body sealing thread processing --- employees in the process of self-inspection inspection personnel on the product after processing products after the inspection.

12, valve body connection thread processing.

13, in the hole processing.

14. Inspectors conduct general inspections.

15. Qualified semi-finished products are sent to the semi-manufactured warehouse.

16, semi-finished products are electroplated.

17, semi-finished plating surface treatment inspection.

18. Inspection of various accessories (balls, stems, seal seats).

19, assembly shop for product assembly - assembly line inspection personnel to test the product.

20, the assembled product undergoes stress testing and drying into the next process.

21, the assembly shop for product packaging ---- packaging line inspection personnel on the product's tightness, appearance, torque testing. Unqualified products must never be packaged.

22. Qualified products are bagged and sent to the finished product warehouse.

23. All inspection records will be stored in a computer for reference at any time.

24. Qualified products are sent to domestic and foreign countries through containers.