Research and development of plastic spring

Because plastic springs have the advantage that steel springs are difficult to replace, the United States, Britain, Japan and other countries are racing to develop and have achieved many research results, and some have been put into practical applications. Its development has generally gone through three stages.
Before 1970, it was the exploration stage of principle experiments. At this stage, there are more published applied theory analysis articles and phased research reports. During this period, because the thermosetting plastics suitable for engineering applications are still in the early stage of development, the development of engineering plastic springs encountered many problems, such as poor temperature resistance, low hardness and wear resistance, high prices, and difficulty in making a wide range of Coil springs, coupled with design procedures, processing equipment, and process parameters have encountered some new problems to be solved, thus delaying the progress of plastic springs to practical applications.

Before 1980, it was the stage of practical development. At this stage, due to the development of the plastics industry, fiber-reinforced plastics (FRP=Fiberglass Rein-forced Plastics) that are temperature-resistant, wear-resistant and reasonably priced have been successfully developed, coupled with the development of automobile design in the direction of miniaturization and light weight, especially for petroleum Since the crisis, in order to reduce the weight of auto parts and save fuel, auto manufacturers have actively developed plastic leaf springs, which has promoted the development of plastic springs to practical applications. The outstanding development result at this stage is the practical application of FRP leaf springs in the United States.

Measures to improve spring quality

(1) Thermomechanical heat treatment–combining steel deformation strengthening and heat treatment strengthening to further improve the strength and toughness of steel. Thermomechanical heat treatment is divided into high, medium and low temperature. High temperature thermomechanical heat treatment is quenched immediately after deformation occurs in a stable austenite state, and can also be combined with forging or hot rolling, that is, quenched immediately after hot forming. Thermomechanical treatment has been used in the production of automobile leaf springs. (60Si2Mn)
(2) Austempering of springs-Austempering can be used for springs with small diameters or sufficient permeability. It can not only reduce deformation, but also improve strength and toughness. It is best to perform tempering again after austempering. The elastic limit can be increased, and the tempering temperature is the same as the austempering temperature.

(3) Spring relaxation treatment-the spring works under the action of external force for a long time, and the result of stress relaxation will produce a small amount of permanent (plastic) deformation, especially the spring that works at high temperature, the stress relaxation phenomenon is more serious at high temperature. Reduce the accuracy of the spring, which is not allowed for general precision springs. Therefore, this kind of spring should be relaxed after quenching and tempering-pre-load the spring so that its deformation exceeds the deformation that may occur when the spring is working. Then heat it at 20C higher than the working temperature for 8-24h.

(4) Low-temperature carbonitriding-the process of combining tempering and low-temperature carbonitriding (soft nitriding) can significantly improve the fatigue life and corrosion resistance of the spring. This process is mostly used for coil springs.

(5) Shot peening-surface defects such as scratches, folds, oxidative decarburization, etc. tend to become stress concentration places and sources of fatigue fracture during spring operation. If a small steel shot is used to spray the surface of the spring at high speed, it will not only improve the surface quality of the spring, increase the surface strength, and put the surface in a state of compressive stress, thereby increasing the fatigue strength and service life of the spring.

Operation precautions

(1) Check the surface for defects such as decarburization and cracks before heat treatment. These surface defects will seriously reduce the fatigue limit of the spring.

(2) The quenching heating should pay special attention to prevent overheating and decarburization, do a good job in salt bath deoxidation, control the furnace gas atmosphere, and strictly control the heating temperature and time

(3) In order to reduce the deformation, the method of loading the spring during heating, the form of fixture and the method of quenching during cooling.

(4) Tempering as soon as possible after quenching, and heating as much as possible. Quick cooling after tempering can prevent temper brittleness and cause surface compressive stress, and improve fatigue strength.

quality inspection

Before heat treatment–

(1) The rolled surface of steel is often the surface after the spring is made, so there should be no cracks, folds, scars, hair lines, bubbles, interlayers, and pressed oxide scales.

(2) Surface decarburization will significantly reduce the fatigue strength of the spring. The depth of the decarburized layer should be inspected as required.

After heat treatment–

(1) There should be no cracks, corrosive pitting and severe quenching deformation when observing the spring watch with the naked eye or low-power magnifying glass.

(2) The hardness and its uniformity meet the requirements. In mass production, it is allowed to use a file to sample the hardness, but it must be noted that the position of the file mark should not affect the final accuracy of the spring.

(3) The metallographic structure should be troostite or a mixed organization of troostite and sorbite.

(4) After the leaf spring is assembled, the permanent deformation and static deflection test under working load are usually carried out.

Types, characteristics and applications of hot work die steel

Types, characteristics and applications of hot work die steel
In recent years, my country has done a lot of work in the research and development of new type die steels,

The localization research has provided the market with high-quality and cheap die steel. The following briefly introduces the types and application progress of hot work die steel

Overview.

1. Has been included in the national standard hot work die steel

The hot work die steel series has been included in the national standard “GB/T1299-2000 Alloy Tool Steel”, which can be divided into main chemical components

W series, Cr-Mo series, Cr-W-Mo series and other types.

3Cr2W8V(H21) steel, with high thermal strength, high thermal stability, good wear resistance and process performance, working temperature

Reach 650°C. Disadvantages: severe segregation of carbides, better plasticity, toughness, thermal conductivity, resistance to cold and heat fatigue and corrosion resistance

difference. my country was introduced from the former Soviet Union in the 1950s. It has a short service life, high alloying degree and high cost. At present, it has basically

Eliminated. Due to the limitation of steel grade and technology, my country is still in mass production and use.

4Cr5MoSiV(H11) and 4Cr5MoSiV1(H13) steel have high hardenability and hardenability, high toughness, high thermal strength and wear resistance

Performance, the use temperature of 590 steel has fine and even carbide distribution, good cold and hot fatigue resistance and corrosion resistance, cold and hot processing performance

it is good. H13 steel (an improved version of H11 steel) is currently the main material for hot forging steel and cold forging die sleeves in China, and it is also a highly versatile hot

As die steel, it is an ideal steel to replace 3Cr2W8V steel, and its life can be increased by 2-3 times.

4Cr3Mo3SiV(H10) steel has high toughness, high resistance to high temperature softening and medium level of wear resistance. Can replace

3Cr2W8V steel making hot extrusion die. The thermal stability of 4Cr5W2VSi steel is higher than that of H13 and H21 steel, and its toughness is between H13 and H21.

Appropriate high-speed upsetting die, the service life is 0.5-1 times longer than H21 steel.

3Cr3Mo3W2V (HM1) steel has excellent strength and toughness, high thermal strength, wear resistance, tempering stability, and resistance to cold and heat fatigue

Good working performance, hot and cold processing performance, working temperature above 700℃. The steel has strong versatility and is suitable for production at high temperature, high speed,

The performance of the mold working under high load, rapid cold and hot conditions is better than 4Cr5W2VSi and 3Cr2W8V steel, and the mold life is longer than

3Cr2W8V steel raises the standard by 2-3 times.

5Cr4W5MoV(RM2) steel has a working temperature of 700℃, which has high tempering resistance and thermal stability, and high thermal strength.

High temperature hardness and wear resistance, but its toughness and thermal fatigue resistance are lower than H13 steel. Suitable for production with high high temperature strength and

The anti-wear hot work die can replace 3Cr2W8V steel, and the die life can be increased by 2-4 times.

The 5Cr4Mo3SiMnVAl(012AI) steel has a working temperature of 700℃ or higher, and has high thermal strength, high temperature hardness, and anti-return

Fire stability, wear resistance and thermal fatigue resistance, toughness and thermal processing plasticity are good, and the nitriding performance is good. Can replace 3Cr2W8V steel mold

The life span can be increased by 3-5 times.

2. Part of the hot work die steel series has been included in the ministerial standard

4Cr40Mo2WSiV (YB/T210-1976) steel has high thermal stability, toughness, wear resistance and crack resistance, and its stability

Qualitatively better than 4Cr5W2VSi and 4Cr5MoSiV1 steel, it is similar to 3Cr2W8V steel.

3Cr2W8MoV (JB/T6399-1992) steel is an improved type of 3Cr2W8V steel.

3Cr3Mo3VNb (HB5137-1980) steel is a kind of ultra-high strength and toughness hot work die steel.

4Cr5MoSiV1, 4Cr5W2VSi, 3Cr2W8V steel has higher high temperature toughness, thermal stability, thermal strength, wear resistance and resistance

Thermal fatigue performance, good cold and hot processing performance. spring

3. Part of the trial hot work die steel series are not included in the standard

3Cr3Mo3V steel has moderate thermal stability, hardness, heat fatigue resistance and toughness.

5Cr4Mo3W2V steel is used as a hot press forging die.

The highest temperature of 4Cr3Mo2V steel reaches 700℃, which is suitable for hot extrusion die.

The working temperature of 4Cr3MoSiV steel reaches 700℃, and the code is CH75.

For 3Cr3Mo3W2VRE steel, 0.06% RE is added to 3Cr3Mo3W2V steel to refine grains and significantly improve plasticity, toughness and life.

4Cr5MoWVSi steel has better thermal strength than H13 steel, with good toughness and thermal fatigue resistance, code H12, suitable for hot extrusion

Die, upsetting die. Tension spring

4Cr3Mo2NiVNb (code HD) steel, all kinds of hot work molds; 4Cr3Mo2NiVNbB (code HDB) steel, improved fracture

Crack toughness and thermal fatigue resistance.

The working temperature is above 700℃, and the service life is 2-2.5 times higher than that of 3Cr2W8V steel.

5Cr4W3Mo2VSi and 5Cr4W3Mo2VNb steel, codenamed 50Si, 50Nb, base steel. Suitable for hot extrusion die.

4Cr5Mo2SiMnV1 (code Y10) and 4Cr3Mo3W4VTiNb (code GR) steel, a new type of hot work die steel, longer service life

3Cr2W8V steel is 2-6 times higher than the standard, suitable for high manufacturing temperature, long contact time with workpiece, easy to cause thermal deformation, collapse or thermal wear

Failed mold. Tension spring

6W8Cr4VTi (code LM1) and 6Cr5Mo3W2VSiTi (code LM2) steel, with good thermal strength, high isothermal

Strength, high temperature hardness, tempering stability and wear resistance are good. Both cold and hot molds use steel, and the mold life is several times longer than 3Cr2W8V steel.

4Cr3Mo2MnVB (code ER8) and 4Cr3Mo2MnVNbB (code Y4) steel, die life is 2-4 times that of 3Cr2W8V steel,

Hot extrusion die steel. Extension spring

Common measurement units (new and old) comparison conversion

The name of the quantity
The symbol of the amount

The name and symbol of the legal unit

Name and symbol of abolished unit

Conversion relationship between statutory and abolished units

Force, gravity

F, W

New [ton] N
Kilonewton [ton]kN

Kgf
Ton-force tf

1kgf≈9.8N
1tf≈9.8kN

Pressure, pressure, stress

P

Pa [ska] Pa
Dry Pa[ska]kPa
Mega Pa [ska] MPa

Kgf/m? kgf/m?
Kgf/cm? kgf/cm?
Kgf/mm? kgf/mm?

1kgf/m?=9.8Pa一10Pa
lkgf/cm?=O.098MPa
lkgt/mm?≈9.8MPa
1MPa=10.1972kgf/cm?
lPa=1N/m2
1MPa=1N/mm?

Features

W, E

Joo [ear] J

Kgf·m

1kgf?m≈9.8J
1J=1N·m

Calories

Q

Joo [ear] J

Thermochemical calth
15°C cal15
International Steam Meter Card

lcalth=4.184J
lcal15=4.1855J
lcal1T=4.1868J

Thermal conductivity

Enter

Watt [te] per meter
Text)W/(m·K)

Kcal/(meter·hour·degree)
kcal/(m·h·℃)
Card/(cm·sec·open)
cal/(cm·s·K)

1kcal/(m.h·℃)=1.163W/(m·K)
lcal/(cm?s·K)=418.68W/(m·K)

Specific heat capacity

C

Joules per kilogram
[尔文]J/(kg·K)

Card/(gram·degree)
cal/(g·℃)

lcal/(g?K)=4186.8J/(kg?K)

Resistivity

P

Micro ohm [m] meter μΩ·m

Ohm·mm?/m
Ω·mm?/m

1Ω·mm?/m=lμΩ·m

Conductivity

K

West [menzi] per meter s/
m

1/(ohm·meter)
l/(Ω·m)

1S/m=l/(Ω·m)

Permeability

μ

Millihenry [li] per meter
mH/m

High [s] every o [ster] Gs/Oe

1mH/m=800Gs/Oe
1Gs/Oe=1.25μH/m

Magnetic flux density,
Magnetic induction

B

T [Sla] T

Gaussian Gs

1Gs=10-4T
1T=10000Gs

Magnetic field strength

H

A [A] per meter A/m

Oster 0e

1Oe=79.6A/m
1A/m=0.0125 Oe

Coercivity

Hc

Ampere per meter
A/m

Oster 0e

10e=79.6A/m
1A/m=0.01250e

Impact toughness

ak

Joules per square
M J/m?

Kgf·m/c
M?kgf·m/cm?

1kgf·m/cm?=9.8067J/cm?
1J/cm?=0.102kgf?m/cm?

Shock absorption work

Ak

Joo [ear] J

Kgf·m

1kgf?m=9.8067J
1J=0.109kgf?m

Commonly used steel theoretical weight calculation formula

Material name

Theoretical weight (kg/m)

Remarks

Flat steel, steel plate, strip steel

W=0.00785×width×thickness

1. The specific gravity of steel is calculated at 7.85 g/cm3

Fang Gang

W=0.00785×side length 2

Round steel, wire, steel wire

W=0.00617×diameter 2

2.f value: the general model and the one with a is 3.34, the one with b is 2.65, and the one with c is 2.26

Hexagonal steel

W = 0.0068 × distance between opposite sides 2

Octagonal steel

W=0.0065×diagonal distance 2

Steel Pipe

W=0.02466×wall thickness×(outer diameter–wall thickness)

Equilateral Angle Steel

W=0.00785×side thickness×(2 side width-side thickness)

3.e value: the general model and the one with a is 3.26, the one with b is 2.44, and the one with c is 2.24

Unequal angle steel

W = 0.00785 × side thickness × (long side width + short side width-side thickness)

I-beam

W=0.00785×waist thickness×〔height+f×(waist width-waist thickness)〕

Channel steel

W=0.00785×waist thickness×〔height+e×(leg width-waist width)〕

4. All length units in the table are calculated in millimeters

Pressure Switch

The pressure switch is a simple pressure control device. When the measured pressure reaches the rated value, the pressure switch can send out an alarm or control signal.
The working principle of the pressure switch is: when the measured pressure exceeds the rated value, the free end of the elastic element is displaced, and the switching element is pushed directly or after comparison to change the on-off state of the switching element to achieve the purpose of controlling the measured pressure.

The elastic elements used in the pressure switch include a single coil spring tube, diaphragm, diaphragm, bellows, etc.

Switching elements include magnetic switches, mercury switches, micro switches and so on.

There are two types of pressure switches: normally open and normally closed.

There are two adjustment modes of the pressure switch, two-position type and three-position type.

Accuracy: A value indicating the accuracy of the equipment, including linearity, tolerance, hysteresis, repeatability, etc. At present, the highest accuracy of pressure switch in Nagano can reach ±0.5% F.S. The model is CB33.

Maximum pressure (Max.P): the maximum value of the pressure range.

Full scale (F.S): The difference between the maximum and minimum pressure range.

Disconnection difference (dead zone): refers to the difference between the switch setting action value and the reset value. For example, when the set value is 1MPa and the actual reset value is 0.9MPa, the connection and disconnection difference is 0.1MPa.

Operating temperature: refers to the temperature range within which the internal mechanism and sensitive components of the instrument will not undergo continuous deformation during operation. Generally, the recommended operating temperature range of pressure switches is -5~400C. If the medium temperature is too high, you can consider adding an accessory siphon (filled) to achieve the purpose of cooling.

S.P.D.T (Single Pole Double Throw): Consists of a normally open, a normally closed contact and a common terminal.

D.P.D.T (Double Pole Double Throw): It consists of a symmetrical left and right common terminal and two groups of normally open and normally closed terminals.

Upper limit one contact (normally open): When the pressure rises to the set value, the contact will act and the circuit will be turned on.

Lower limit one contact (normally closed): When the Yali drops to the set value, the contact will act and the circuit will be turned on.

Upper and lower limit two contacts HL: It is a combination of upper limit and lower limit, divided into two types of independent action of two contacts (dual setting, double loop) and simultaneous action of two contacts (single setting, double loop).

Upper limit 2 contact: Combining two upper limit forms, divided into two types of independent action of two contacts (dual setting, double circuit) and simultaneous action of two contacts (single setting, double circuit).

Lower limit 2 contacts: Combining two lower limit forms, divided into two types of independent action of two contacts (dual setting, double circuit) and simultaneous action of two contacts (single setting, double circuit).

Pressure resistance: The maximum pressure that the pressure switch can withstand while maintaining its normal performance. However, when the pressure switch is used in overpressure situations, the sensitive components will undergo continuous deformation, and the pressure setting value will change at this time, and the pressure switch will not be able to perform its normal performance and may even be damaged.

Finite Element Analysis of the Stiffness Characteristics of Leaf Spring

Leaf springs are elastic components widely used in automobiles, and stiffness is an important physical parameter. Therefore, before the product is trial-produced, how to calculate its actual stiffness more accurately has become a common concern. Traditional calculation methods, such as “common curvature method” and “concentrated load method”, have certain limitations, and it is often necessary to add empirical correction coefficients to adjust the calculation results. With the development of computers, the finite element method has gradually been applied to the design of leaf springs due to its high accuracy, good convergence, and convenient use. Zou Hairong et al. applied the finite element method to analyze the abnormal fracture problem of a certain graded stiffness leaf spring, and proposed improvement measures to avoid such fracture. Hu Yumei et al. applied Ansys software to analyze the static strength characteristics of the leaf spring of a certain automobile rear suspension, and gave the stress distribution of the leaf spring under different loads. The calculation results are in good agreement with the test. Gu Antao discussed the general process of applying the finite element method to design leaf springs and gave a design example.

One of the biggest advantages of the finite element method is that it can simulate the actual working state of the design object, so it can partially replace the experiment and guide the precise design. Automotive leaf springs have nonlinear and hysteresis characteristics. When applying the finite element method for analysis, large deformation and contact need to be considered, that is, geometric nonlinearity and state nonlinearity need to be considered at the same time. This will make the calculation not easy to converge, so higher solving skills and analysis strategies are required.

This paper uses Nastran’s nonlinear analysis module to analyze the stiffness characteristics of a leaf spring, and discusses the effect of friction on its performance. The analysis process and results can provide references for the design of similar products.

2 Calculation method of leaf spring stiffness

The traditional calculation methods include “common curvature method” and “concentrated load method”. In addition, domestic scholar Guo Konghui proposed a calculation method called the master piece analysis method for the inherent defects in the common curvature method, and Tian Guangyu et al. proposed an improved concentrated load method for the inherent defects of the concentrated load method. The starting point of these methods is to regard the leaves of the leaf spring as a cantilever beam of equal cross-section. The friction between the leaves of the leaf spring and the large deformation characteristics during the deformation of the leaf spring are not considered. The classical beam formula is used to calculate the first leaf End deflection, and then obtain the stiffness of the leaf spring.

2.1 Common curvature method

The common curvature method was proposed by Parsilowski of the former Soviet Union. The basic assumption is that after the leaf spring is loaded, each blade has the same curvature in any section, that is, the entire leaf spring is regarded as a variable section beam. The formula for calculating the stiffness of the symmetrical leaf spring is as follows:

2.2 Concentrated load method

The basic assumption of the concentrated load method is that the leaves of the leaf spring only contact each other at the ends, that is, it is assumed that there is only one contact point at the end between the ith piece and the i-1th piece, and the contact force is Pi, and at the contact point The deflection of two adjacent blades is equal. Among them, P1 is the external load on the first piece. Therefore, there are n-1 unknown forces in the system P2, P3,…, Pn, n-1 equations can be obtained by equal deflection at the contact point, and the unknown forces P2, P3,…, Pn, and then calculate the end deflection of the first piece based on the load received by the first piece, and then the stiffness of the leaf spring can be obtained. The formula for calculating the stiffness of the leaf spring is as follows:

2.3 The main film analysis method

The common curvature method assumes that each blade has the same curvature on any cross section after the leaf spring is loaded. There is an obvious inconsistency in this assumption, that is, there is no concentrated bending moment at the free end of each leaf. It cannot be equal to the curvature of the same section of the previous one. For this reason, the main film analysis method has made the following assumptions.

a. Each leaf spring is divided into a constrained part and a non-constrained part. The definitions of the constrained part and the non-constrained part of the i-th leaf spring are shown in Figure 1.

b. The leaves of the leaf spring are free to deform downward in the unconstrained part, and the constrained part conforms to the assumption of common curvature, that is, the curvature of each section in this section is the same as that of the previous one.

Based on the above assumptions, the formula for calculating the stiffness of the leaf spring is as follows:

The meaning of each symbol in the formula is the same as above, where an+2=an+1=l1.

2.4 Improved concentrated load method

The concentrated load method assumes that each leaf of the leaf spring is in contact with each other only at the ends, but in fact the points in the leaf spring may also be in contact with each other. Based on this idea, the improved concentrated load method proposes the following assumptions.

a. There are not only interactions between the end points, but also several contact points. As shown in Figure 2, there are Ni contact points between the i-th slice and the i-1th slice. Record these points to The distance of the symmetry plane of the leaf spring is lij, j=1, 2,…, Ni.

b. The interaction between the i-th slice and the i-1th slice is concentrated only at the preset Ni contact points, denoted as Pi1, Pi2, PiNi, as shown in Figure 2.

Similar to the concentrated load method, there are total unknown forces in the system. From the equal deflection at the contact points, one equation can be obtained, and the magnitude of each unknown force can be obtained by solving this equation system. According to the force on the first piece, the end deflection of the first piece can be obtained, and then the stiffness of the leaf spring can be obtained.

Unlike the concentrated load method, the results calculated by this method cannot guarantee that each unknown force is greater than or equal to zero (that is, there can only be pressure between the contact points). For this reason, iterative algorithms are needed to solve this problem.

The common point of the above calculation methods is that the leaves of the leaf spring are approximately equivalent to a cantilever beam, and the contact between the leaves is simulated by different methods. In fact, the leaf spring has large deformation characteristics when it is working, and there is a certain deviation in the linear cantilever beam simulation, and the contact simulation method between the leaf springs is also rough. Using the finite element method to calculate the leaf spring stiffness can overcome the above shortcomings and make the calculation more accurate. Moreover, the working stiffness of variable section springs, less leaf springs and gradual stiffness leaf springs can be obtained very well, which has practical significance.

The working principle of shot blasting machine

The working principle of shot blasting machine:
Shot blasting is a shot blasting surface treatment method that has been applied in developed countries in Europe and America. The world’s first shot blasting equipment was born 100 years ago, and it was first used in various metal or non-metal surfaces to remove impurities, oxide scale, and increase roughness. After a hundred years of development, the shot blasting process and equipment have become quite mature, and its application has not only been in various heavy industry factories. With the birth of the world’s first horizontally mobile shot blasting equipment in the United States, BLASTRAC, its application fields have rapidly expanded to concrete surface coating treatment and ship deck metal surface treatment, and directly lead the industry’s standards Formulate and industry construction method specifications.

With the continuous improvement of Baretech shot blasting equipment and mature technology, shot blasting technology and equipment have entered the fields of road maintenance, bridge construction and airport maintenance in developed countries in Europe and America. However, China’s application in this area is still very small. Only a few projects have used shot blasting processing technology, and there is still a blank in the waterproof coating of highways, municipal roads and concrete bridges. Gui Shi Di (GSD) hopes to use this article to introduce this new shot blasting process to colleagues in the maintenance and construction of highway and bridge engineering, and hopes that this new process and technology will be promoted.

1. Shot blasting process and working principle of shot blasting equipment

Shot blasting means that the shot material (steel shot or sand grain) is projected onto the working surface at a high speed and at a certain angle by a mechanical method, so that the shot material hits the working surface, and then cleaned by the airflow of the matching vacuum cleaner inside the machine , The technology of recycling the pellets and the cleaned impurities separately, and making the pellets reusable. The shot blasting machine is equipped with a dust collector, which can achieve dust-free and pollution-free construction, which improves efficiency and protects the environment. Shot blasting machines can be divided into three types according to their walking forms: hand-push type, vehicle-mounted type and self-propelled type.

During the operation of the shot blasting machine, by controlling and selecting the particle size and shape of the shot, and adjusting and setting the walking speed of the machine, the shot flow rate is controlled to obtain different shot strengths and different surface treatment effects.

1.2 Control of the quality of surface shot blasting

The shot blasting process and shot blasting equipment use three parameters to control the surface condition after treatment according to the different surfaces to be treated. Choose the size and shape of the pellets; the walking speed of the equipment; the flow rate of the pellets. The above three parameters cooperate with each other to obtain different treatment effects and ensure the ideal roughness of the surface after shot blasting.

For example: using S330 steel shot, flow rate 10A, processing C50 concrete surface, it can reach a roughness of 90; processing asphalt surface can remove the oily layer while reaching a roughness of 80; when processing steel plates, it can reach the cleanliness standard of SA3.

Roller-type shot blasting machine: It uses a high-speed impeller to throw projectiles to the castings and forgings that are constantly turned over by the roller to remove oxide scale, so that the surface of the workpiece can be uniformly cleaned, showing the original metal color.

Crawler shot blasting machine: the workpiece is loaded by high-strength wear-resistant rubber track or manganese steel track, and the high-speed projectile is thrown on the track by the shot blasting device to achieve the purpose of cleaning.

Rotary shot blasting machine: The surface of the workpiece is hit by a uniform steel shot through the frequency conversion shot blasting machine, and the coverage rate of the steel shot on the surface reaches more than 98% to achieve the strengthening effect.

Hanging chain stepping shot blasting machine: adopts multi-station fixed-point projection cleaning method to remove the sticky sand and oxide scale on the surface of the casting, so that the casting reproduces the metal color.

Quality control method of heat treatment production process

As we all know, heat treatment is an important part of mechanical manufacturing engineering by changing the material organization to obtain the required performance of mechanical parts or products and to ensure the use of safe and reliable processes. Because the quality characteristics of heat treatment are that the results cannot be fully verified by subsequent inspections and tests, and the negative effects and economic losses caused by quality problems in the heat treatment are very large, in the GB/T19000 series of standards, heat treatment is To be recognized as a “special process”, special measures need to be taken to implement quality control of all employees, comprehensive, and entire process. Due to the differences in heat treatment equipment, personnel quality, parts technical requirements, production guidelines, process technology and production management levels of domestic enterprises, there are also differences in the special measures adopted to control the quality of parts or products, and heat treatment has continuous production. The characteristics of the operation, therefore, it is very important to seek a quality control method in the production process to meet and improve the quality of heat-treated parts, especially mass-produced parts.

2 The main content of the production process quality control method

2.1 Change the ideas and concepts of quality assurance model

In the past, our thoughts and concepts for the quality assurance model and quality management focus of heat-treated parts remained in the tradition of relying solely on final inspection to check, focusing only on quality results, and not focusing on the control of quality formation and eliminating heat treatment defects. In the process of quality formation, there have been parts defects or missed inspections, resulting in a certain quality loss. All kinds of personnel are busy processing the results of the parts every day, the result is that the busier the more chaotic, repetitive and low-level errors occur repeatedly, and the work is abnormally passive. We learned from the pain, calmly summarized and learned the lessons of failure, looked for and explored successful methods, and re-understood and positioned the key tasks of quality management.

Through learning the relevant content of heat treatment standards and learning from the experience of successful heat treatment management enterprises, it is clear that improving the quality of heat treatment must first change the thinking and concepts of various personnel on the quality assurance mode. That is to say, the traditional passive check by the final inspection is transformed into a prevention Mainly, the active control quality assurance model that combines prevention and inspection has established clear responsibilities, standardized management, strict rewards and punishments, and unified professional technology, management technology, and scientific methods, as well as full participation, full process control, and comprehensive management. Three-pronged approach” process quality control management ideas and concepts. The results of several years of implementation show that:

Tool selection and cutting amount determination

The selection of cutting tools and the determination of cutting parameters are important contents in the CNC machining process. It not only affects the machining efficiency of CNC machine tools, but also directly affects the machining quality. The development of CAD/CAM technology makes it possible to directly use CAD design data in CNC machining, especially the connection between a microcomputer and a CNC machine tool, so that the entire process of design, process planning and programming is completed on the computer, generally without output Special process documents.

Nowadays, many CAD/CAM software packages provide automatic programming functions. These softwares generally prompt the relevant issues of process planning in the programming interface, such as tool selection, machining path planning, cutting amount setting, etc. The programmer only needs to set the relevant The parameters can be automatically generated and transferred to the CNC machine tool for processing. Therefore, the selection of tools and the determination of cutting parameters in CNC machining are completed in the state of human-computer interaction, which is in sharp contrast with ordinary machine tool processing. At the same time, programmers must master the basic principles of tool selection and cutting parameters. Fully consider the characteristics of CNC machining when programming. This article discusses the tool selection and cutting parameters that must be faced in NC programming, gives some principles and suggestions, and discusses the issues that should be paid attention to.

1. Types and characteristics of commonly used tools for CNC machining

CNC machining tools must adapt to the high-speed, high-efficiency and high degree of automation characteristics of CNC machine tools. Generally, they should include general-purpose tools, general-purpose connection tool holders and a small number of special-purpose tool holders. The tool holder must be connected to the tool and mounted on the power head of the machine tool, so it has gradually been standardized and serialized. There are many ways to classify CNC tools. According to the tool structure, it can be divided into: ①Integral type; ②Inlaid type, using welding or machine clamp connection, machine clamp type can be divided into two types: non-indexable and indexable; ③Special types, such as composite tools, reduce Vibrating knives, etc. According to the materials used to manufacture the tools, it can be divided into: ① high-speed steel tools; ② carbide tools; ③ diamond tools; ④ tools of other materials, such as cubic boron nitride tools, ceramic tools, etc. From the cutting process, it can be divided into: ① turning tools, including outer circle, inner hole, thread, cutting tools, etc.; ② drilling tools, including drills, reamers, taps, etc.; ③ boring tools; ④ milling tools, etc. . In order to meet the requirements of CNC machine tools for tool durability, stability, easy adjustment, and exchangeability, in recent years, machine-clamped indexable tools have been widely used, reaching 30% to 40% of the entire CNC tools. Metal removal The amount accounts for 80% to 90% of the total.

Compared with the tools used on ordinary machine tools, CNC tools have many different requirements, mainly with the following characteristics:

⑴ Good rigidity (especially rough machining tools), high precision, vibration resistance and small thermal deformation;

⑵Good interchangeability, convenient for quick tool change;

⑶ High life, stable and reliable cutting performance;

⑷The size of the tool is easy to adjust to reduce the tool change adjustment time;

⑸ The tool should be able to reliably break or roll chips to facilitate the removal of chips;

⑹Serialization and standardization to facilitate programming and tool management.

Second, the choice of CNC machining tools

The selection of the tool is carried out under the man-machine interaction state of CNC programming. The correct selection of tools and tool holders should be based on the processing capacity of the machine tool, the properties of the workpiece material, the processing procedure, the cutting amount and other related factors. The general principle of tool selection is: convenient installation and adjustment, good rigidity, high durability and precision. On the premise of meeting the processing requirements, try to choose a shorter tool holder to improve the rigidity of tool processing.

When selecting a tool, the size of the tool must be adapted to the surface size of the workpiece. In production, end mills are often used to process the peripheral contours of flat parts; when milling planes, you should choose carbide blade milling cutters; when processing bosses and grooves, choose high-speed steel end mills; processing rough surfaces or rough machining When drilling holes, you can choose corn milling cutters with carbide inserts; for the processing of some three-dimensional profiles and variable bevel contours, ball end milling cutters, ring milling cutters, tapered milling cutters and disk milling cutters are often used.