What makes a difference on Quality of impactor blow bars.

When it comes to Quality of blow bar, the wear life is always the most considered but also reliability is as same important. A good blow bar should last long and maintain an even wearing face till the end of wear life, at the same time doesn’t break. What is essential to make a good blow bar? Below is the answer.

Correct ingredients of material

This is the basis and foundation of a good blow bar. The elements must be at a correct percentage by weight and the hazard chemicals such as S and P must be as low as possible. Some elements such as Mo and Ni are must be added within a correct range to achieve the targeted property. Also, the scrap content in material should be at a decent grade and not exceed a certain percentage. However, higher grade of material will push up the cost of material and make a big difference on the cost of blow bar.Quality of blow bar

Correct and good design of casting system

This is always ignored by foundry. A good casting system will maximumly reduce the defects or failures in the casting. This is always relying on foundry engineers’ experience, knowledge and research on metallurgy.

Quality of blow bar

Mold quality and design

A blow bar is born in a mold. A good mold should be robust in material, correct for size and easily operated for molding. As explained above, an integrated mold is always the first choice for reliably creating the blow bar even though is more expensive.

Quality of blow bar

Pouring

Pouring is not simply dumping the melt steel liquid into the sand flask. A correct pouring with correct speed and precise temperature control is very important to secure the quality of casting. A small error of pouring will lead to big defect or failure inside the casting, especially for the ceramic blow bars which is extremely sensitive to metallurgy and temperature.

Quality of blow bar

Head treatment

Head treatment shapes the mechanical characteristics of a blow bar. A correct heat treatment will empower the blow bar with excellent anti-wear performance against abrasion as well as good toughness against impact. Heat treatment will make a big difference on the performance of blow bars. Heat treatment is the art of temperature which also heavily rely on the experience, knowledge and operation control of engineers.

Quality of blow bar

Machining

Machining is always difficult on the blow bars as the base material is always hard for milling. A good machining will make the correct fitting size and sufficient contact areas in rotor of impact crusher.

Quality of blow bar

Inspection

In foundry no one is 100% sure that every casting is done perfect. Inspection is the only way to find out the unqualified ones and make sure every piece of blow bar that handed over to customer is in correct size and good quality. Inspection must be carried out everywhere in the whole process of manufacturing.

Quality of blow bar

Foundry management

A high-level foundry management is to get production timely organized, correctly and safely operated, and every product is made in accordance with requirements and with unqualified product is internally rejected. All is all, a high-level managed foundry is more likely to get quality secured and reliable in a long time.

Quality is not simply created by using the good material. It’s a combination of all above and more factors. To make a good blow bar, all things must be done 100% correct.

Quality of blow bar

For more technical spec and application advice, please visit www.sunwillmachinery.com

Watch the foundry video for blow bar manufacturing Sunwill Machinery – YouTube

How is impact crusher blow bar made & What makes a difference on Quality?

Blow bar is the essential wear parts for impact crusher (HSI). Normally the blow bars are made by casting in foundry in a few types of alloy steel below to suit the various working conditions of crushers.

Chrome steel 

Feature: excellent wear resistance but brittle.

Typical applications: secondary or tertiary crushing with abrasive and small size feed and no tramp goes iron into feed.

Chrome steel matrix with ceramic honeycomb inlaid

Feature: an upgraded chrome steel blow bar with better wear performance but same brittleness.

Typical applications: where the chrome steel blow bars are used.

impact crusher blow bar

Martensitic alloy steel

Feature: lower wear performance but tougher than chrome steel

Typical applications: concrete recycling crushers or crushing with large feed or a little tramp iron content.

impact crusher blow bar

Martensitic alloy steel matrix with ceramic honeycomb inlaid

Feature: an upgraded martensitic steel blow bar with better wear performance but same toughness.

Typical applications: where the martensitic alloy steel blow bar is used.

impact crusher blow bar

Manganese steel

Feature: the lowest wear performance but toughest

Typical applications: primary limestones crusher or crushing with largest feed or big tramp iron into feed.

Manganese steel with Titanium carbide columns inserted

Feature: an upgraded manganese steel blow bars with better wear performance but same toughness.

Typical applications: where the manganese steel blow bar is used.

impact crusher blow bar

Customized steel

Feature: special chemicals or mechanical property for specific working conditions.

Blow bars are always made with sand casting started from a timber or steel mold. Some foundry makes it with lost-foam casting from a pattern cut from foam. Normally the blow bars made by sand casting have better metallurgy quality and finer finishing but the cost is relatively higher than blow bars made from foam casting. Blow bars made in martensitic steel must be made by sand casting because it has a lower carbon content and very sensitive in metallurgy, while the foam casting will have a big contamination in the metal from the foam burning.

impact crusher blow bar made

Below is the manufacturing process of blow bars made by sand casting:

Mold/Pattern preparation.

The blow bars mold is normally made from timber and created by CNC machine. The molds are generally sorted in two types – single mold & integrated mold. The single mold is just the core part of casting created, while the integrated mold is a whole casting system created including the holding frames and positioning pins. The integrated mold is more expensive than single mold but it is more friendly for operation and more reliable for the pattern quality.

impact crusher blow bar made

Molding

A blow bar pattern is created in the sand flask with the mold. After a series of processing including cleaning, coating and drying, the pattern is ready for pouring. In addition, the ceramics or titanium carbides are fixed in the pattern if it is a ceramic or Tic inserted blow bar.

impact crusher blow bar made

Pouring

The raw materials are mixed up and melt in the furnace. Many types of chemical additives are added and some physical measures is necessary to purify the metal liquid. Before and during pouring the temperature of steel liquid must be precisely controlled and pouring must be continuous for a blow bar. Also, the samples of metal must be prepared for every melting for chemical analysis and traceable records.

impact crusher blow bar made

Cleaning

After the casting is cooling down and solidified, the sands, ingates and risers on blow bar billet is cleaned and removed.

Heat treatment

The blow bar billets are treated with several loops of heating up and cooling down to get the proper mechanical properties. Heat treatment is a crucial part to secure the quality and performance of blow bars. The temperature and heating time must be precisely set based on the material and size of blow bar, and rate of heating and cooling also must be correct.

impact crusher blow bar made

Grinding and machining

Heat-treated blow bars are blasted and ground with the burrs and edges removed. The blow bar must be carefully ground to avoid any cracks due to grinding heat. Machining on the fitting areas on some types of blow bar must be done to ensure it is straight and flat for fitment in rotor of crushers.

impact crusher blow bar made

Coating and packing

Blow bars are always coated for anti-rust purpose also in different color for materials identification. Robust and seaworthy package is also necessary for the final packing.

Coating and packing Blow bars

Inspection

Inspection is an important part of blow bar manufacturing. Inspection must be in place in every procedure of manufacturing from raw materials to final packing, including chemical analysis, surface defect, inner quality, dimension, hardness, microstructure, toughness, finishing, color, labeling and more if necessary.

impact crusher blow bar Quality

Foundry management

A high-level foundry management is to get production timely organized, correctly and safely operated, and every product is made in accordance with requirements and with unqualified product is internally rejected. All is all, a high-level managed foundry is more likely to get quality secured and reliable in a long time.

Quality is not simply created by using the good material. It’s a combination of all above and more factors. To make a good blow bar, all things must be done 100% correct.

 

For more technical spec and application advice, please visit www.sunwillmachinery.com

Watch the foundry video for blow bar manufacturing Sunwill Machinery – YouTube

How and how much does ceramic blow bar increase its wear life?

Blow bar or break bar is the hammer mounted on HSI – Horizontal Shaft Impactor functioned to break the rocks, stones, concretes or other stuff that need to be reduced size. The working principle is simple. The horizontally positioned rotor in impactor is driven by a motor to rotate at a very high speed. Blow bars that are vertically inserted or clamped in rotor rotate as well. When the rocks or stones fed into the impactor, it’s hit by the rotating blow bars back and forth and shattered into small pieces.

In this crushing process, blow bars are subjected to serve abrasion from the rocks also strong impact force at high speed. Blow bars wear quickly and need to be replaced frequently. The blow bars replacement is very costly in terms of spare cost, down time and labor. and also bring the potential injuring risk to workers during the process of replacement. Hence, the longer lasting blow bars are desperately wanted by the crusher operators.

In this crushing process, blow bars are subjected to serve abrasion from the rocks also strong impact force at high speed. Blow bars wear quickly and need to be replaced frequently. The blow bars replacement is very costly in terms of spare cost, down time and labor. and also bring the potential injuring risk to workers during the process of replacement. Hence, the longer lasting blow bars are desperately wanted by the crusher operators.

 

Blow bars are normally made of the alloy steels including manganese steel, martensitic steel or chrome steel. The wear life of blow bars depends on the hardness of alloy steel made of. Due to the limit of mechanical property of alloy steel, it is too difficult to make it very hard but doesn’t break when receive the impact force meanwhile at a bearable cost.

 

In this circumstance, ceramic blow bar is invented by engineers and has been proven the most efficient solution to increase wear life of blow bars. Ceramic blow bar is also made of alloy steel casting but with high hardness industrial ceramics embedded. The ceramics is originally made in tiny particles and processed to a honeycomb cube. Ceramic honeycomb is placed at the wearing areas and bonded with the metal fluid when the blow bar is cast in foundry. After the casting solidified, the ceramics forms a very hard section on blow bar. The hard ceramic sections provide excellent wear performance and increases wear life when blow bar works for crushing in impactor, but doesn’t compromise the ability of whole blow bar to withstand impact force.

 

Ceramic blow bars can usually achieve a doubled life span of the conventional mono-alloy blow bars. In some cases the wear life can be increased by 200%. However, as the ceramic only increases the wear performance of blow bar but doesn’t do anything to the impact-resistant performance, when select blow bars the crushing conditions is still necessary to be taken into consideration. For example, when crush demolished building concretes in large size, the blow bars are usually made of martensitic steel, In this condition, martensitic steel blow bar with ceramic is also the only option for longer wear life.

 

Besides the longer wear time, ceramic blow bars also help to increase the productivity per hour of impact crusher because the rougher surface and sharper edges of blow bar also increase the crushing efficiency. Ceramic blow bars usually produce 5%-10% more in every hour than the mono-alloy blow bars.

Normally ceramic blow bars are recommended for secondary and tertiary crushing or recycling concretes and asphalt. Chrome ceramic blow bars are usually a good solution for secondary and tertiary crushing and martensitic ceramic blow bars for recycling concrete. While ceramic is not a solution for manganese steel blow bars for primary crushing with very large stone crushed.

Compared with mono-alloy blow bars, ceramic blow bar is a big challenge to be manufactured. It requires the foundry to have more advanced casting technology and equipment, higher-level manufacturing management and quality control standards. Only a few foundries are capable of manufacturing the ceramic blow bars reliably in the world. Sunwill Machinery is among the top with their over 10 years of manufacturing experience of ceramic blow bars. Watch the video of foundry to see more https://youtu.be/d8aqjsawwj0

How to avoid breakage on blow bars in impact crusher？

Blow bar is the core wear parts in the horizontal shaft impactor or impact crusher. Working in very high speed to break the stones and feed stuff down to smaller size, blow bars have to withstand severe abrasion and impact force during the operation. Also, as the feed materials are not always pure and in a controlled size, the condition in crusher is more complicated. As a result, breakage of blow bars happens sometimes in impact crushers which can lead to reduced performance and increased maintenance costs.

(Below is a case of high chrome blow bar breakage caused by tramp iron that was not allowed to feed in)

What could be done to avoid the breakage of blow bars? Here are some steps you can take:

Choose the right blow bars: The right blow bars for your impact crusher will depend on the type of material you are crushing and the operating conditions. Choose blow bars made from high-quality materials that are designed for your specific application. The materials of blow bars include manganese steel, manganese steel with tic inserts, martensitic steel and martensitic with ceramic inserts, chrome white iron and chrome with ceramic inserts.

Check for proper fit: Ensure that the blow bars are properly fitted in the rotor and do not have any wobbling or loose parts. If the blow bars are not securely fastened, they are more likely to break.

Maintain the right feed size: The feed size of the material you are crushing is important to avoiding blow bar breakage. If the feed size is too large, it can cause excessive stress on the blow bars and increase the risk of breakage. Keep the feed size within the recommended range for your impact crusher.

Monitor the rotor speed: The rotor speed of the impact crusher should be carefully monitored and kept within the recommended range. If the rotor speed is too fast, it can cause excessive stress on the blow bars and increase the risk of breakage.

Use the correct blow bar design: Different blow bar designs are suitable for different applications. Choose the correct blow bar design for your application to ensure maximum performance and reduced risk of breakage.

Regularly inspect the blow bars: Regular inspections of the blow bars can help to identify any potential issues before they become serious. Check for cracks, chips, or other signs of wear and replace the blow bars as needed to maintain optimal performance.

Implement a preventive maintenance program: Implementing a preventive maintenance program can help to reduce the risk of blow bar breakage by ensuring that all parts of the impact crusher are functioning properly and are in good condition. Regular maintenance and inspections can help to identify potential issues early and reduce the risk of downtime due to breakage.

By following these steps, you can avoid blow bar breakage and ensure that your impact crusher operates at peak performance.

Also, blow bars are made by steel foundries. A good foundry will not only understand the blow bars on metallurgy basis but also be very familiar with the crushing applications very well. A good foundry will ensure that the blow bars are made in good and reliable quality to avoid any breakage due to quality issue.

Sunwill Machinery is a foundry with over 15 years’ experience in the manufacturing and service of blow bars also a leading MMC ceramic blow bars manufacturer in the world. Sunwill Machinery is able to provide various materials suit different applications, also the metallurgists and engineers know how to make the blow bars right for customer’s specific applications.

How to select right blow bars for horizontal shaft impactor?

Horizontal Shaft Impactor (HSI) is a type of heavy machines works to crush the rocks, stones, concretes, asphalts or other objects which need to be size reduced for preparation of next procedure in quarry, mining, cement, construction industry.

HSI impact crusher mainly consists of a motor, a rotor, aprons, impactor housing and blow bars. Working principle of a impactor is the motor drives the horizontally mounted rotor as well as the blow bars which are mounted on the rotor rotating at very high speed. The objects feed from the open inlet of impactor are hit by the blow bars towards the impact plates which are mounted on the aprons and bounced back. The objects are shattered and size reduced during this process and discharged from the outlet of impactor.

Blow bar is the key and largest wear part on impactors. As the rotor runs at very high speed, blow bars withstand huge shock and sever abrasion from the crushed objects. Blow bars are the most frequently replaced wear parts and account for a big part of operation cost of impactor. Making the blow bars works longer is so crucial to keep the impactor run time and cost efficiently.

Any failure with the blow bars costs a high lost on time and money. A good blow bar should not only last as long time as possible but also works safely without breakage. That means the blow bar must have good resistance to wear and enough resistance to impact at the same time. How to make the blow bars last longer? The answer is on the materials that blow bars are made of and the foundry where it is made by.

The crushing applications are always various due to the different natures and different sizes of crushed objects. To have the best performance in different applications, blow bars are normally made in following materials to have different natures in terms of wear and impact resistance.

Manganese steel

Manganese steel is a kind of austenitic steel with around 13% or 18% content of Manganese. It is featured with very good impact resistance but low wear resistance. Manganese steel is the first option for blow bars which used on primary or second crushers with large feed size, usually over Dia. 800mm, or applications with high content of unbreakable objects come into the impactors. A typical application of manganese blow bars is crushing the limestones in quarry plants of cement plants.

Manganese steel with Titanium Carbide (TIC) columns inserted

Due to the nature of low wear resistance of manganese steel, Titanium Carbide columns (TIC) are sometimes inserted into the wear face of manganese steel blow bars to increase its wear performance. With TIC inserts, service life of manganese blow bars could be up to 60% increased but the cost of blow bars is higher.

Martensitic alloy steel

Martensitic steel is a type of alloy steel with Molybdenum, Nickel and other alloy ingredients in its compositions. It is featured with better wear performance than manganese steel but impact performance is compromised. This nature enables martensitic blow bars to achieve better wear life in applications where the feed size is smaller or a little content of unbreakable objects contaminated. A typical application of martensitic steel blow bars are used on impactors recycling the concretes with rebars content.

Martensitic alloy steel with ceramic inserted

To obtain longer wear life of martensitic steel blow bars, industrial ceramic grits could be inserted in the martensitic steel matrix of wear areas. Thanks to the excellent wear performance of ceramics, the martensitic steel blow bars could have 100% longer wear life. However, the cost of blow bars is about 50% increased with the ceramic inserted.

Chrome white iron

Chrome white iron has higher content of carbon and chromium than manganese steel and martensitic steel, which gives chrome white iron blow bars outstanding wear performance but very low impact resistance. Chrome white with about 20% content of chromium is normally named medium chrome and around 25% is named high chrome. Blow bars made of chrome white iron are the first option for impactors crush very abrasive rocks on secondary or tertiary crushers. The size of rocks feed into the impactor must be strictly controlled, usually less than dia. 300mm, and any unbreakable objects or iron tramp is NOT allowed in feeding. A typical application of chrome white iron blow bars is used to crush natural stones or granites in aggregates or sand-making plants.

Chrome white iron with ceramic inserted

To further obtain longer wear life of chrome white iron blow bars, ceramic grits are also inserted at the wear areas. The wear life of chrome blow bars could be 100% increased but cost is also about 50% increased. Furthermore, Sunwill has special grade chrome ceramic blow bars in C650 grade, which is able to achieve up to 170% increase on wear life in very abrasive secondary or tertiary crushing applications.

All blow bars are originally made in foundries. A good foundry will not only provide the good and reliable quality of blow bars, but also be able to provide versatile and innovative solutions for specific applications at metallurgical basis.

Sunwill Machinery is a foundry with over 15 years’ experience in the manufacturing and service of blow bars. Sunwill Machinery is able to provide all above materials suits different applications, also the metallurgists and engineers know how to make the blow bars right for customer’s specific applications.

 

Please visit Sunwill Machinery at www.sunwillmachinery.com or drop an email at info@sunwillmachinery.com when you have any questions about the blow bars for impactors or need a site specific solution. We are happy to assist at any time.

Other topics about Sunwill Blow Bar

Part 1:Blow bars selection guidance and Impactor brands list

Part 2:How to make a good blow bar

Part 3:Optimal wear solutions for impact crushers